Postnatal growth velocity and overweight in early adolescents: A comparison of rural and urban African boys and girls

O iginal Resea ch A icle Pos na al G ow h Veloci y and O e weigh in Ea ly Adolescen s: A Compa ison o Ru al and U ban A ican Boys and Gi ls E.D. CHIRWA, 1 * P. GRIFFITHS, 1,2 K. MALETA, 3 P. ASHORN, 4 J.M. PETTIFOR, 1 AND S.A. NORRIS 1 1 Wi s/MRC De elopmen al Pa hways o Heal h Resea ch Uni , Depa men o Pedia ics, Facul y o Heal h Sciences, Uni e si y o he Wi wa e s and, Johannesbu g, Sou h A ica 2 Cen e o Global Heal h and Human De elopmen , Loughbo ough Uni e si y, Loughbo ough, Leices e shi e, LE 11 3TU, Uni ed Kingdom 3 Depa men o Communi y Heal h, College o Medicine, Uni e si y o Malawi, Malawi 4 Depa men o In e na ional Heal h, School o Medicine, Uni e si y o Tampe e, Finland and Depa men o Pedia ics, Tampe e Uni e si y Hospi al, Finland Objec i es: To compa e g ow h eloci y o wo A ican child coho s and examine he ela ionship be ween pos na al g ow h eloci y in in ancy/ea ly childhood and he isk o o e weigh /s un ing in ea ly adolescence. Me hods: The s udy used da a om wo child coho s om u ban (Bi h o Twen y Coho , Sou h A ica) and u al (Lungwena Child Su i al S udy, Malawi) A ican se ings. Mixed e ec modelling was used o de i e g ow h and peak g ow h eloci ies. T- es s we e used o compa e g ow h pa ame e s and eloci ies be ween he wo coho s. Linea and logis ic eg ession models we e used o de e mine he ela ionship be ween g ow h eloci y and ea ly adolescen (ages 9–11 yea s) body mass index and odds o being o e weigh . Resul s: Child en in he BH coho we e signi ican ly alle and hea ie han hose in he Lungwena coho , and exhibi ed as e weigh and heigh g ow h eloci y especially in he i s yea o li e (P<0.05). No signi ican associa- ion was shown be ween baseline weigh (a w ) and o e weigh in ea ly adolescence (OR 51.25, CI 50.67, 2.34). The weigh g ow h eloci y pa ame e b w was highly associa ed wi h odds o being o e weigh . Associa ion be ween o e - weigh in adolescence and weigh eloci y was s onge in in ancy han in ea ly childhood (OR a 3 mon hs 54.80, CI 52.49, 9.26; OR a 5 yea s 52.39, CI 51.65, 3.47). Conclusion: High weigh and heigh g ow h eloci y in in ancy, independen o size a bi h, is highly associa ed wi h o e weigh in ea ly adolescence. Howe e , he long e m e ec s o apid g ow h in in ancy may be dependen on a pa icula popula ion’s socio-economic s a us and le el o u baniza ion. Am. J. Hum. Biol. 26:643–651, 2014. V C2014 The Au ho s Ame ican Jou nal o Human Biology Published by Wiley Pe iodicals, Inc. Se e al s udies ha e shown he associa ion be ween ea ly childhood g ow h and la e heal h ou comes such as diabe es, ca dio ascula diseases, and obesi y (Came on and Deme a h, 2002; Came on e al., 2003; Adai , 2007; Adai e al., 2009). In pa icula , s udies ha e examined he c i ical pe iods in in ancy and ea ly childhood ha a e associa ed wi h hese heal h ou comes (Black and K ish- nakuma , 1999; McCa hy e al., 2007; Bo on e al., 2008; Ridgway e al., 2009). Bo h g ow h e a da ion and apid g ow h in he di e - en s ages o ea ly li e a e p edic i e o he la e heal h ou - comes (Came on and Deme a h, 2002; Li, 2003; Came on e al., 2005; S ein e al., 2010). Fo example, Flexede e al. (2012) ound ha apid weigh gain in in ancy is associa ed wi h physician-diagnosed as hma in school-aged child en (Flexede e al., 2012). A numbe o s udies ha e examined he ela ionship be ween ea ly g ow h and la e heal h ou comes in high income as well as low and middle income coun ies (LMIC; Ma o ell, 1995; Ong e al., 2000; Li, 2003; Salonen e al., 2009; Mesa e al., 2010; S ein e al., 2010). Howe e , he e ha e also been inconsis en indings ega ding he ela ionship be ween g ow h e a da ion, o s un ing and o e weigh and obesi y in la e li e. Whe eas, i has been sugges ed ha childhood unde -nu i ion p e- disposes a child o weigh gain in la e li e (Ho man e al., 2000), o he s udies ha e ound ha childhood s un ing was associa ed wi h lowe body mass index (BMI; Sch oede e al., 1999; Walke e al., 2007). Se e al s udies ha e also shown he sho e m and long e m bene i s o apid g ow h o child en in esou ce-poo se ings (Vic o a e al., 2001; Kalanda e al., 2005; Hoddino e al., 2008; Vic o a e al., 2008). The sho e m bene i s include, educed mo bidi y and mo - ali y, and imp o ed cogni i e de elopmen , while long e m bene i s include imp o ed human capi al and imp o ed ep oduc i e ou comes in women. Al hough a wide body o e idence suppo s he long e m bene i s and de imen al e ec s o ea ly apid g ow h in LMIC, ew s udies ha e looked a his ela ion- ship in a sub-Saha an A ican con ex , due o he limi ed numbe o bi h coho s udies. Thus, his s udy compa ed he g ow h eloci ies o wo coho s om u al and u ban A ican se ings, and examined he ela ionship be ween size a bi h (bi h weigh ), g ow h eloci y in in ancy and This is an open access a icle unde he e ms o he C ea i e Commons A ibu ion License, which pe mi s use, dis ibu ion and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. Con ac g an sponso s: Conso ium o Ad anced Resea ch T aining in A ica (CARTA) which is—join ly led by he A ican Popula ion and Heal h Resea ch Cen e and he Uni e si y o he Wi wa e s and and unded by he Welcome T us (UK); Con ac g an numbe : 087547/Z/08/ Z; Depa men o In e na ional De elopmen (D ID) unde he De elop- men Pa ne ships in Highe Educa ion (DelPHE); he Ca ne gie Co po a- ion o New Yo k; Con ac g an numbe : B 8606; Fo d Founda ion; Con ac g an numbe : 1100-0399; Google.O g; Con ac g an numbe : 191994; SIDA; Con ac g an numbe : 54100029; MacA hu Founda ion; Con ac g an numbe : 10-95915-000-INP. *Co espondence o: Esna D. Chi wa, MRC/Wi s De elopmen al Pa h- ways o Heal h Resea ch Uni , Facul y o Heal h Sciences, Uni e si y o he Wi wa e s and, 7 Yo k Road, Pa k own 2193, Johannesbu g, Sou h A ica. E-mail: Esna .Chi[email p o ec ed] Recei ed 31 Oc obe 2013; Re ision ecei ed 30 Ap il 2014; Accep ed 28 May 2014 DOI: 10.1002/ajhb.22575 Published online 20 June 2014 in Wiley Online Lib a y (wileyonlinelib a y.com). V C2014 The Au ho s Ame ican Jou nal o Human Biology Published by Wiley Pe iodicals, Inc. AMERICAN JOURNAL OF HUMAN BIOLOGY 26:643–651 (2014) ea ly childhood, and ea ly adolescen obesi y. The wo coho s a e likely o be a di e en s ages o nu i ional ansi ion, conside ing he u al coho is om a e y low income coun y while he u ban coho is om a middle income coun y. U baniza ion is gene ally linked o changes in li es yle ac o s ha a ec obesi y isk, such as die a y pa e ns and seden a y beha io s. Thus, apa om he nu i ional di e ences, he e may also be social, cul u al, economic and en i onmen al di e ences be ween he wo coho s ha may a ec g ow h and de elopmen o he child en and also a ec hei isk o obesi y. Mixed-e ec s modelling and childhood s uc u al g ow h model we e used o examine he ela ionship be ween pos na al g ow h eloci y and obesi y o s un ing in ea ly adolescence (ages 9–11 yea s). Mixed-e ec s mod- elling is lexible in dealing wi h unbalanced longi udinal measu emen s, and akes in o accoun co ela ions be ween epea ed measu emen s. The use o he s uc- u al g ow h cu e allowed o he es ima ion o he g ow h a es a any gi en age. SUBJECTS AND METHODS Weigh and heigh measu emen s om 2 A ican longi- udinal coho s we e used. The Bone-Heal h (BH) S udy is a sub-sample o he Bi h- o-Twen y (BH) bi h coho in Johannesbu g, Sou h A ica, which includes 453 black pa icipan s. The coho has an h opome ic measu e- men s a bi h, 3 mon hs, 6 mon hs, 1 yea , 2 yea s, 4 yea s, 5 yea s, 7/8 yea s, 9 yea s, and 10 yea s. Bi h weigh s we e ex ac ed om bi h eco ds, while subse- quen weigh /heigh measu emen s we e ob ained using s anda d an h opome ic echniques (Came on, 1984). Mo e speci ic de ails abou his u ban coho a e epo ed elsewhe e (Came on e al., 2003; Came on e al., 2005). The u al componen o he s udy used he Lungwena Child Su i al S udy (LCSS), which is a coho o abou 729 child en li ing in Mangochi, a u al dis ic in sou h- e n Malawi. The on-going s udy has g ow h da a o chil- d en om bi h o 16 o 17 yea s o age. The an h opome ic da a in his coho we e collec ed mon hly om bi h un il 18 mon hs, 3 mon hly un il 60 mon hs, hen a 6 yea s, 8–9 yea s, 10 yea s, 12 yea s, and 15 yea s. Weigh and heigh we e measu ed du ing home isi s, using po able sp ing-scales and sel -made leng h boa ds, ha ing eading inc emen s o 100 g and 5 mm, espec i ely. Mo e speci ic de ails o he Lungwena coho a e epo ed elsewhe e (Espo e al., 2002; Male a e al., 2003). In bo h coho s, g ow h eloci ies we e de i ed om a s uc u al g ow h model i ed o g ow h da a om bi h o 60 mon hs. The exclusion c i e ia and he o e all num- be o pa icipan s a ailable o analysis a e shown in Figu e 1. Because o di e ences in he socio-economic s a us (SES) a iables collec ed in he wo coho s, an SES sco e was calcula ed sepa a ely o each coho . The SES a ia- bles in he BH coho included household asse s such as ca , TV, idge and washing machine, and household acili- ies such as ype o wa e sys em, oile ype and elec ic- i y. The SES a iables o he Lungwena coho included owne ship o land, a m animals, bicycle, and adio, amongs o he s and household a iables such as ma e nal and pa e nal li e acy le el. In each coho , an asse sco e was ini ially de i ed based on household asse s. P incipal componen analysis was hen used o de i e an o e all SES sco e by combining he asse sco e wi h o he house- hold and communi y SES a iables. Fig. 1. Flowcha o he samples a ailable o analysis om he wo coho s. 644 E.D. CHIRWA ET AL. Ame ican Jou nal o Human Biology A Be key-Reed i s o de model (Be key, 1982) was i - ed using mixed e ec s modelling. The model has he unc ional o m; y5a1b 1cln ðÞ1d= : whe e y5weigh o heigh o child a age , he unc ion pa ame e ais ela ed o he baseline weigh o heigh a bi h, bis ela ed o he linea componen o he g ow h eloci y, cis ela ed o he decele a ion in g ow h eloci y and d ep esen s an in lec ion poin ha allows g ow h eloci y o peak a e bi h a he han a bi h (Mook- Kanamo i e al., 2011). The model was modi ied as sugges ed by Simondon e al. (1992), so ha i is de ined a bi h ( 50) as ollows: y5a1b 1cln 11ðÞ1d=ð 11Þ: P e ious analyses ha e shown his model o ha e op i- mum i o he BH coho g ow h da a (Chi wa e al., 2014). The model was used o desc ibe g ow h pa e ns in ea ly childhood a e adjus ing o ma e nal cha ac e is- ics (ma e nal heigh and age), SES and ges a ional age. Sepa a e models we e i ed o boys and gi ls in each coho . The i s o de de i a i e o he model was hen used o de i e weigh and heigh eloci ies o e ime (Bo - on e al., 2008; Mook-Kanamo i e al., 2011). The g ow h eloci y unc ion was hen used o de i e he peak weigh eloci y (PWV), peak heigh eloci y (PHV) and he age a which a child eached i s PWV (APWV) and i s peak heigh eloci y (APHV). The p ima y ou comes we e BMI and he p opo ion o child en who we e o e weigh in he 9–11 yea age g oup. BMI cu -o cha s o child en we e used o calcula e co esponding o e weigh cu -o s (Cole e al., 2000, 2007). The de i ed pa ame e es ima es, g ow h eloci y, in an peak eloci y and he age a peak eloci y we e used as p edic o s o adolescen BMI o obesi y. T- es s we e used o compa e weigh , heigh g ow h eloci y, peak g ow h eloci y be ween boys and gi ls wi hin and be ween coho s. Linea eg ession was used o examine he ela ionship be ween BMI- o -age z-sco es (BMIZ) in la e childhood and ea ly adolescence (9–11 yea s) and p e- dic o s, adjus ing o bi h weigh , sex and coho di e - ences. Logis ic eg ession was hen used o explo e p edic o s o obesi y, adjus ing o coho di e ences and bi h weigh . Analysis was done using S a a Ve sion 11, and all s a is ical es s we e pe o med a 5% signi icance le el. The BH s udy was app o ed by he Human Resea ch E hics Commi ee o he Uni e si y o Wi wa e s and, while he LCSS was app o ed by he Malawi Na ional Heal h Science Resea ch Commi ee. RESULTS Desc ip i e s a is ics The p opo ion o boys in he BH coho was highe han ha o gi ls (57% s. 43%), while he p opo ion o boys and gi ls in he Lungwena coho was almos he same (51% s. 49%). O he 216 child en in he BH coho , almos hal we e i s bo n, while only 19% o he 341 chil- d en om he Lungwena coho we e i s bo n. The a e - age ma e nal age o he BH coho was 25 yea s (wi h s anda d de ia ion (SD) o 5.9), while he a e age age in he Lungwena coho was 26 yea s (SD 56.5). BH coho mo he s we e on a e age alle han hei Lungwena coun e pa s (158 cm s. 155 cm). Table 1 shows he mean an h opome ic measu emen s in in ancy/ea ly childhood and la e childhood/ea ly adoles- cence be ween boys and gi ls in he wo coho s. The e we e no signi ican di e ences in he a e age size a bi h be ween he coho s (P>0.05). Howe e , BH boys and gi ls expe ienced mo e apid weigh gain om 3 mon hs TABLE 1. Compa ison o physical g ow h measu emen s be ween boys and gi ls in he wo coho s NBoys Gi ls nBoys Gi ls Sig 1 Sig 2 Bi h and ea ly childhood Weigh (kg) Bi h weigh 216 3.2 60.5 3.1 60.4 341 3.3 60.5 3.2 60.5 0.115 0.070 3 mon hs 82 6.5 60.8 5.8 60.7 274 6.0 60.8 5.5 60.7 <0.001 <0.001 6 mon hs 52 8.1 60.9 7.4 61.0 286 7.2 61.0 6.6 60.9 0.011 <0.001 1 yea 193 9.7 61.4 9.2 61.3 302 8.4 61.1 8.0 61.1 0.012 0.002 2 yea 153 11.8 61.7 11.4 61.4 308 10.5 61.4 10.1 61.3 0.126 0.010 4 yea 210 15.5 61.9 14.9 61.8 326 14.6 61.5 14.0 61.6 0.021 <0.001 5 yea 187 18.6 62.0 17.9 62.1 338 16.0 61.8 15.5 61.9 0.022 0.016 Heigh (cm) Bi h leng h – – – 341 48.9 62.2 47.9 62.1 - <0.001 3 mon hs 82 60.8 62.9 58.7 62.8 274 57.3 62.4 56.1 62.6 0.001 <0.001 6 mon hs 52 66.3 62.8 63.4 64.1 286 62.5 62.6 60.6 62.6 0.015 <0.001 1 yea 187 74.4 63.1 72.6 63.0 302 69.0 62.6 67.8 62.6 <0.001 <0.001 2 yea s 143 83.6 63.7 82.2 63.1 308 78.2 63.7 76.9 63.4 0.010 0.002 4 yea s 210 99.2 63.9 97.9 63.9 326 93.9 64.3 92.4 64.4 0.017 0.002 5 yea s 187 108.8 64.0 107.4 64.2 338 100.9 64.4 99.4 64.7 0.022 0.003 Ea ly adolescence Age (yea s) 216 10.5 60.3 10.5 60.3 341 10.3 60.3 10.3560.3 <0.001 0.011 Heigh (cm) 216 137.8 66.1 138.4 65.9 341 129.765.5 128.46 66.0 <0.001 <0.001 Weigh (kg) 216 32.966.2 33.4 66.6 341 25.7 63.2 25.22 63.5 <0.001 <0.001 BMI (kg/m 2 ) 216 17.362.5 17.4 62.9 341 15.3 61.2 15.22 61.2 <0.001 <0.001 O e weigh (%) 26(21%) 22(24%) 2(1.2%) 0(0%) <0.001 <0.001 Unde weigh (%) 1(0%) 5(5%) 13(8) 17(10%) <0.001 0.246 Sig 1 : BH boys s. Lungwena boys. All mean compa isons done using - es . Sig 2 : BH gi ls s. Lungwena gi ls. All p opo ions compa isons done using Fishe s’ exac es . POSTNATAL GROWTH AND OBESITY IN EARLY ADOLESCENTS 645 Ame ican Jou nal o Human Biology onwa ds as shown by he signi ican di e ences in mean weigh om 3 mon hs, wi h BH boys and gi ls weighing on a e age mo e han hei Lungwena coun e pa s. Al hough he e we e no da a on bi h leng h o he BH coho , subsequen measu emen s showed BH boys and gi ls we e on a e age signi ican ly alle han hei Lung- wena coun e pa s. In ea ly adolescence, he e we e no signi ican di e en- ces in weigh , age, heigh o BMI be ween boys and gi ls wi hin each coho , bu he e we e signi ican di e ences be ween he coho s, wi h BH boys and gi ls ha ing highe mean BMI, heigh and weigh compa ed o he Lungwena boys and gi ls. Howe e , unlike he pa e n in in ancy/ea ly childhood, gi ls in he BH coho we e on a e age alle and weighed mo e han boys a ages 9/10 yea s. Figu e 1 shows he dis ibu ion o BMI o boys and gi ls in he wo coho s, wi h BH child en ha ing la gely highe BMI han Lungwena child en. Howe e , he e is also wide a ia ion in he BMI alues in he BH coho (Fig. 2). A e age model pa ame e and g ow h eloci y es ima es Pa ame e es ima es o weigh and heigh models we e de i ed o each child using he andom componen s o he mixed models. A - es compa ison o hese pa ame e es i- ma es showed signi ican di e ences in he a e age pa am- e e es ima es be ween BH boys and Lungwena boys o bo h he heigh and weigh g ow h model (Table 2). Simila esul s we e also ound amongs he gi ls om he wo coho s. BH boys had he highes s a ing alues (a w and a h ), as well as he highes linea g ow h a es (b w and b h ). Howe e he a h o he heigh model o bo h coho s ep e- sen s s a ing heigh /leng h a 3 mon hs, due o he BH coho no ha ing heigh /leng h measu emen s a bi h. Wi hin each coho , he e gene ally we e no signi ican di - e ences in model pa ame e es ima es be ween boys and gi ls in bo h coho excep o b w and b h in he Lungwena coho . Non-signi ican di e ence in he linea componen o he eloci y cu e be ween boys and gi ls in he Lungwena coho was also shown by he non-signi ican di e ences in bo h weigh and heigh eloci ies. The e we e signi ican di e ences in he weigh eloci y be ween boys and gi ls in he BH coho excep a 24 mon hs. Al hough boys in he Lungwena coho ended o ha e highe weigh eloci ies han gi ls, he e we e no signi i- can di e ences in a e age weigh eloci y be ween boys and gi ls in he Lungwena coho om 12 mon hs onwa ds. Boys in he BH coho gene ally exhibi ed highe heigh eloci ies han gi ls, wi h signi ican di e ences in he a e age heigh eloci y be ween boys and gi ls in he i s 2 yea s o li e (P<0.001). As expec ed and consis en wi h he changes in a e age weigh and heigh o e ime, as shown in Table 1, weigh and heigh eloci ies we e highes in he i s 12 mon hs, wi h g ow h a es apidly declining om 12 mon hs (Table 2). The e we e no signi ican di e ences in he a e age weigh eloci ies be ween small o ges a ional age in an s (WAZ a bi h <22) and app op ia e o ges a- ional age (AGA) in an s (da a no shown). Simila esul s we e ound when compa ing hose wi h low bi h weigh (bi h weigh <2.5 kg) o hose wi h no mal bi h weigh (da a no shown). The signi ican di e ences in he pa ame e es ima es be ween BH boys and Lungwena boys as well as be ween gi ls in he wo coho s, we e also shown by he signi ican di e ences in he weigh and heigh eloci ies be ween he coho s, wi h he BH boys ha ing highe g ow h a es han hei Lungwena coun e pa s. Simila ly, BH gi ls exhibi ed highe g ow h a es han Lungwena gi ls. A s ong posi i e linea ela ionship be ween weigh and heigh eloci y ( 50.89, P<0.001) was obse ed. BH gi ls had he highes in ancy PWV (1.39 kg/mon h). Howe e , no signi ican di e ence was obse ed in he Fig. 2. BMI in ea ly adolescence o boys and gi ls in he wo coho s. 646 E.D. CHIRWA ET AL. Ame ican Jou nal o Human Biology in ancy PWV o PHV be ween sexes wi hin he Lungwena coho o as well as be ween gi ls in he wo coho s. BH boys which had he smalles PWV also had he younges age a APWV. BH boy’s heigh eloci y also peaked ea - lies compa ed o he o he h ee g oups. Rela ionship be ween bi h weigh , g ow h eloci y, peak eloci y and adolescen BMI The e we e no signi ican co ela ions be ween bi h weigh and weigh eloci y ( 520.08, P50.06) o heigh eloci y ( 520.05, P50.27). The e was a posi i e bu weak ela ionship be ween bi h weigh and adolescen BMI, wi h bi h weigh only explaining 1% o he a ia ion in BMI (Table 3). This ela- ionship did no change e en a e adjus ing o sex di e - ences. Howe e , when coho di e ences we e aken in o accoun , he o al a ia ion explained by he model inc eased om 1% o 24%, signi ying he la ge di e ences ha exis be ween he wo coho s. The e ec o bi h weigh on BMI was also suppo ed by he esul s om he ela ionship be ween a w o he weigh model and BMI, wi h no signi ican sex di e ence being obse ed. Wi hin each o he h ee models using pa ame e es ima es om weigh models, b w had he s onges linea ela ionship wi h BMI compa ed o he o he h ee pa ame e es i- ma es, wi h no linea ela ionship being obse ed be ween adolescen BMIZ and d w . Bo h c w and d w we e non-signi ican when e ec o coho and sex di e ences as well as bi h weigh , we e aken in o accoun . The e was a nega i e linea ela ionship be ween adoles- cen BMIZ and APWV, indica ing ha in an s ha eached hei PWV ea ly we e mo e likely o ha e high BMI in ado- lescence. A s ong nega i e co ela ion was also obse ed be ween PWV and APWV ( 520.53, P<0.001), indica ing ha in an s wi h low PWV we e mo e likely o each hei peak la e han in an s ha exhibi ed high PWV. The e was no signi ican linea ela ionship be ween adolescen BMIZ and age a which he in an eached PHV. The e was a gene al dec ease in he ela ionship be ween weigh eloci y and adolescen BMIZ o e ime e en a e adjus ing o bi h weigh (R 2(3m) 50.38, R 2(60m) 50.29). E en hough he e was a s ong ela ionship be ween adolescen BMIZ and heigh eloci y in he i s 6 mon hs, e en a e adjus ing o bi h weigh , as obse ed om he R 2 alues (models 1 and 2), he e we e no di e ences in he s eng h o he ela ionship o e ime when coho and sex di e ences we e aken in o accoun (model 3). TABLE 2. A e age di e ences in pa ame e es ima es, g ow h eloci y and peak eloci y be ween coho and sex BH coho Lungwena coho Coh. di . Sex di . Boys Gi ls Boys Gi ls M F BH LUN Mean (SD) Mean (SD) Mean (SD) Mean (SD) sig sig sig Sig Pa ame e s (weigh ) a w 6.70 (0.45) 4.44 (0.34) 5.49 (0.66) 5.13 (0.63) aaaa b w 0.16 (0.02) 0.13 (0.03) 0.14 (0.02) 0.14 (0.03) a 0.023 a 0.816 c w 0.42 (0.02) 1.16 (0.03) 0.54 (0.02) 0.48 (0.03) aaaa d w 23.50 (0.03) 21.36 (0.03) 22.68 (0.03) 22.43 (0.03) aaaa Pa ame e s (heigh ) a h 66.5 (2.07) 56.4 (1.95) 54.1 (2.28) 53.5(2.20) aaa 0.030 b h 0.59 (0.04) 0.52 (0.06) 0.52 (0.06) 0.52 (0.07) a 0.815 a 0.654 c h 1.37 (0.03) 4.42 (0.06) 3.79 (0.07) 3.56 (0.08) aaaa d h 239.8 (0.04) 222.6 (0.05) 215.3 (0.06) 216.8 (0.08) aaaa Peak eloci y PWV 1.31 (0.26) 1.39 (0.28) 1.36 (0.24) 1.35 (0.29) 0.067 0.217 0.024 0.579 APWV (mon hs) 2.49 (0.02) 2.86 (0.05) 3.10 (0.06) 2.96 (0.07) aaaa PHV 5.77 (0.37) 5.59(0.58) 5.51 (0.67) 5.53 (0.84) a 0.556 0.006 0.882 APHV (mon hs) 5.00 (0.08) 7.24 (0.34) 6.92 (0.47) 5.43 (0.27) aaaa Weigh eloci y (kg/mon hs) 3 mon hs 0.48 (0.03) 0.50 (0.03) 0.44 (0.03) 0.41 (0.03) aaaa 6 mon hs 0.29 (0.03) 0.33 (0.03) 0.27 (0.03) 0.26 (0.03) aaaa 12 mon hs 0.21 (0.03) 0.23 (0.03) 0.20 (0.03) 0.19 0.03) aaa 0.056 24 mon hs 0.18 (0.02) 0.18 (0.03) 0.17 (0.02) 0.17 (0.03) aa 0.795 0.431 48 mon hs 0.17 (0.02) 0.16 (0.03) 0.15 (0.02) 0.15 (0.03) a 0.103 0.002 0.796 60 mon hs 0.17 (0.02) 0.15 (0.03) 0.15 (0.02) 0.15 (0.03) a 0.540 a 0.873 Heigh eloci y (cm/mon hso) 3 mon hs 3.34 (0.17) 2.99 (0.14) 2.41 (0.10) 2.45 (0.11) aaa 0.002 6 mon hs 1.61 (0.07) 1.62 (0.07) 1.37 (0.08) 1.37 (0.09) aa 0.221 0.468 12 mon hs 0.94 (0.05) 1.00 (0.07) 0.91 (0.07) 0.89 (0.09) aaa 0.144 24 mon hs 0.71 (0.04) 0.73 (0.06) 0.70 (0.07) 0.69 (0.09) 0.134 aa 0.211 48 mon hs 0.64 (0.04) 0.63 (0.06) 0.61 (0.06) 0.60 (0.08) a 0.015 0.019 0.352 60 mon hs 0.63 (0.04) 0.60 (0.06) 0.58 (0.06) 0.58 (0.08) a 0.123 a 0.393 M5BH boys s. Lungwena boys F5BH gi ls s. Lungwena gi ls BH 5BH boys s. BH gi ls LUN 5Lungwena boys s. Lungwena gi ls PWV5Peak weigh eloci y (kg/mon hs) APWV 5Age a peak weigh eloci y (mon h) PHV5Peak heigh eloci y (cm/mon hs) APHV5Age a peak heigh eloci y (mon h) All compa isons done using he - es . a :P- alue <0.001. POSTNATAL GROWTH AND OBESITY IN EARLY ADOLESCENTS 647 Ame ican Jou nal o Human Biology Rela ionship be ween bi h weigh , g ow h eloci y, peak eloci y and adolescen obesi y Table 4 shows he associa ion be ween adolescen o e - weigh and g ow h eloci y. The s udy ound no associa- ion be ween sex and being o e weigh adolescen , e en hough gi ls had lowe odds o being o e weigh compa ed o boys (OR 50.88, P50.671). The Lungwena coho had lowe odds o being o e weigh han he BH coho (OR 50.02, P<0.001). The odds did no change e en a e adjus ing o sex di e ences. Despi e he odds o being o e weigh inc easing wi h inc ease in bi h weigh , he associa ion was no signi ican (OR 51.25, P50.486). Consis en wi h he obse ed ela ionship be ween BMI and linea g ow h a es in weigh (b w )asshownin Table 3, he s udy also ound s onges associa ion be ween being o e weigh and linea g ow h a e in weigh (b w ), e en a e adjus ing o coho di e ences and bi h weigh (OR 52.05, P- alue <0.001). While he e was a s ong associa ion be ween being an o e - weigh adolescen and a child’s es ima ed baseline weigh (a w ), his ela ionship was no signi ican when coho di e ences we e aken in o accoun . A e adjus - ing o coho di e ences and bi h weigh , only he lin- ea g ow h a e unc ion (b w )was ound obeassocia ed wi h adolescen o e weigh . The s udy also ound s ong associa ion be ween adoles- cen o e weigh and linea g ow h a es in heigh , wi h child en exhibi ing as e heigh g ow h a es being mo e likely o be o e weigh in adolescence. Howe e , his ela- ionship was non-signi ican when coho di e ences we e aken in o accoun . Consis en wi h weigh model pa am- e e s, baseline heigh (a h ) and he dec ease in heigh eloci y o e ime (c h ) we e also no associa ed wi h being o e weigh . The logis ic eg ession models showed a s onge associ- a ion be ween o e weigh in ea ly adolescence (ages 9–11 yea s) and weigh gain in in ancy han wi h weigh gain in ea ly childhood. A 3 mon hs, e e y 1 SD inc ease in weigh eloci y had an eigh old odds o being o e weigh in ea ly adolescence. These odds educed wi h age such ha by he ime a child is 5-yea s-old, e e y 1 SD inc ease in weigh eloci y esul ed in almos h ee old odds o being o e weigh . Despi e he e being a dec ease in he odds o being o e weigh a e adjus ing o coho di e - ences and bi h weigh , he end o e ime was he same. The same end was obse ed wi h heigh eloci y. How- e e , he e we e no signi ican associa ion be ween heigh eloci y and being o e weigh a e adjus ing o bi h weigh and coho di e ences. No associa ion was ound be ween obesi y and PHV, age a PHV o age a PWV, TABLE 3. Rela ionship be ween adolescen BMI and g ow h eloci y, peak eloci y and Reed1 model pa ame e s, adjus ing o sex and coho di e ences Main p edic o Model 1 Model 2 Model 3 b(SE) R 2 b(SE) R 2 b(SE) R 2 Sex : boys Re gi ls 20.18 (0.09) a 0.01 Coho : BH Re LUN 21.07 (0.08) 0.22 Bi h weigh 0.27 (0.10) 0.01 Pa ame e s (weigh ) a w 0.34 (0.05) 0.08 0.33 (0.05) 0.08 0.25 (0.06) a 0.27 b w 21.2 (1.55) 0.25 21.3 (1.61) 0.25 18.9 (1.45) 0.42 c w 0.96 (0.18) 0.05 1.00 (0.18) 0.07 0.31 (0.21) a 0.25 d w 20.05 (0.07) a 0.001 20.04 (0.07) a 0.01 0.06 (0.09) a 0.25 Pa ame e s (heigh ) a h 0.08 (0.01) 0.15 0.07 (0.01) 0.15 0.001(0.013) a 0.25 b h 4.32 (0.62) 0.08 4.18 (0.63) 0.08 2.20 (0.60) 0.26 c h 20.24 (0.04) 0.05 20.24 (0.04) 0.06 0.017 (0.05) a 0.25 d h 20.05 (0.01) 0.16 20.05 (0.002) 0.18 0.001 (0.01) a 0.25 In an peak eloci y PWV 1.85 (0.16) 0.20 1.84 (0.16) 0.20 1.86 (0.14) 0.44 PHV 0.35 (0.07) 0.05 0.33 (0.07) 0.05 0.23 (0.06) 0.26 APWV 21.33 (0.19) 0.08 21.39 (0.19) 0.10 1.32 (0.29) 0.27 APHV 20.004 (0.05) a 0.001 20.008 (0.05) a 0.01 0.05 (0.04) a 0.24 Weigh eloci y 3 mon hs 14.8 (0.80) 0.38 14.7 (0.81) 0.38 12.3 (1.05) 0.40 6 mon hs 18.3 (1.03) 0.36 18.2 (1.04) 0.36 14.8 (1.23) 0.40 12 mon hs 21.7 (1.28) 0.34 21.7 (1.31) 0.34 17.4 (1.37) 0.42 24 mon hs 23.5 (1.43) 0.33 23.7 (1.47) 0.33 19.3 (1.42) 0.43 48 mon hs 23.3 (1.50) 0.30 23.5 (1.55) 0.30 19.6 (1.44) 0.43 60 mon hs 22.5 (1.52) 0.29 23.1 (1.57) 0.29 19.5 (1.44) 0.43 Heigh eloci y 3 mon hs 1.31(0.10) 0.24 1.32 (0.10) 0.25 0.81 (0.25) 0.26 6 mon hs 3.68 (0.29) 0.22 3.68 (0.29) 0.24 1.86 (0.50) 0.26 12 mon hs 3.79 (0.54) 0.08 3.72 (0.55) 0.09 1.50 (0.54) 0.26 24 mon hs 3.67 (0.65) 0.05 3.54 (0.65) 0.06 2.22 (0.59) 0.26 48 mon hs 4.07 (0.66) 0.06 3.93 (0.66) 0.07 2.32 (0.61) 0.26 60 mon hs 3.98 (0.65) 0.06 3.83 (0.67) 0.07 2.30 (0.61) 0.26 a E ec o main p edic o was no signi ican . Model 1: Adolescen BMI s. main p edic o . Model 2: Adolescen BMI s. main p edic o (adjus ing o bi h weigh ). Bi h weigh was non-signi ican when adjus ed o he main p edic o s in Model 2. Model 3: Adolescen BMI s. main p edic o (adjus ing o bi h weigh , sex and coho di e ences). R 2 5 o al a ia ion in BMI explained by he o e all model. 648 E.D. CHIRWA ET AL. Ame ican Jou nal o Human Biology when adjus ed o coho di e ence. Howe e child en wi h high PWV we e mo e likely o be o e weigh in ado- lescence e en a e adjus ing o coho di e ences. DISCUSSION This s udy has been able o demons a e a posi i e lin- ea ela ionship be ween apid weigh gain in in ancy and ea ly childhood and ea ly adolescen BMI, as well as shown a ela ionship be ween apid g ow h in he ea ly yea s and he odds o being o e weigh /obese in ea ly adolescence. The high odds a io and R 2 alues be ween g ow h eloci y in he i s yea o li e ( he pe iod which was also cha ac e ised by high g ow h eloci y) and adolescen BMI, highligh he associa ion be ween apid weigh gain and obesi y in ea ly adolescence. The dec easing end in he OR alues in la e ea ly childhood highligh s he c i i- cal pe iod du ing in ancy ha is highly associa ed wi h adolescence/adul obesi y. This suppo s wha p io s ud- ies in he BH coho and o he s elsewhe e ha e ound, albei using di e en me hods o measu es (Came on e al., 2003; Ekelund e al., 2007; McCa hy e al., 2007; Bo on e al., 2008; Adai e al., 2009; Deme a h e al., 2009; S ein e al., 2010). In a s udy o he ela ionship be ween apid weigh gain in he i s 2 yea s o li e and obesi y in childhood in BH child en wi h app op ia e bi h weigh o ges a ional age (AGA), Came on e al. (2003), using weigh - o -age z-sco es, ound ha child en ha exhibi ed apid g ow h in in ancy we e signi ican ly alle , and weighed mo e in childhood. Ou s udy has been able o demons a e his using pa ame e es ima es om he Reed1 model, wi h he pa ame e b w , a unc ion ela ed o g ow h eloci y being highly posi i ely associ- a ed wi h ea ly adolescen BMI. Consis en wi h he s udy by Mook-Kanamo i e al., ou s udy ound high PWV o be highly associa ed wi h ea ly adolescence o e weigh . The signi icance o he ela ionship be ween apid weigh gain in in ancy and adolescen BMI was also highligh ed by he nega i e associa ed be ween APWV and adolescen BMI, indica ing ha in an s ha eached in an PWV ea ly we e mo e likely o ha e high BMI. Apa om ha , ou s udy has also explo ed he ela ionship using heigh eloci y and ex ended he pe iod o ea ly adolescence (9– 11 yea s). Ou s udy has also been able o show simila associa ion be ween apid g ow h and adolescen BMI in a u al popula ion, which is om a p edomina ely mal- nou ished popula ion, wi h high le els o s un ing and unde weigh . The c i ical pe iod o de elopmen is he same in bo h coho s. Howe e , he apid in an g ow h in his u al popula ion seems o ha e bene icial e ec s, as i p o ec s he adolescen child om he e ec s o unde - nu i ion,wi h ew cases o obesi y. The e a e se e al hypo hesised biological ela ionships be ween p ena al and pos na al g ow h and obesi y in la e li e, and a la ge body o e idence suppo s hese hypo hesised ela ionships (Ong and Loos, 2006; Adai , 2007; Ekelund e al., 2007; Jones-Smi h e al., 2007; McCa hy e al., 2007; Chom ho e al., 2008; D ue e al., 2012). These p e ious s udies showed ha ei he small size a bi h, small size a bi h combined wi h as g ow h o as g ow h i sel , ha e e ec s on la e li e heal h ou - comes. S udies ha e also shown ha low-bi h-weigh in an s usually exhibi apid g ow h du ing he i s yea o li e (Ong, 2006; Adai , 2007; Johnson e al., 2012). How- e e , ou s udy which used da a om wo coho s om di - e en se ings in e ms o en i onmen al and socio- economic ac o s, ound no ela ionship be ween size a bi h (bi h weigh ) and g ow h eloci y in bo h coho s. Simila ly, we ound no associa ion be ween size a bi h and o e weigh in ea ly adolescence. Bo h bi h weigh and i s es ima ed pa ame e (a w ) we e no associa ed wi h adolescen o e weigh . The non-signi ican ela ionship be ween bi h weigh and g ow h eloci y as well as wi h o e weigh in ea ly adolescence could also be due o he limi ed ange o bi h weigh measu emen s, since ou sample excluded p e e m babies. E en hough he e was a wide a ia ion in he age o ini ial weigh measu emen s o he Lungwena coho , o babies no deli e ed in a heal h acili y, he mixed e ec s model adjus ed o he age a which he measu emen s we e aken. Howe e , he e ec o he di e ences in he en i on- men al and socio-economic ac o s in he wo coho s we e shown by he di e ences in he g ow h a es and he pos - na al p e alence o s un ing/unde weigh and o e weigh in he coho s as well as he signi icance o coho e m in he models. Despi e he e being no signi ican di e ences in bi h weigh s be ween he wo coho s, he u ban BH child en exhibi ed mo e apid weigh gain in he i s yea TABLE 4. Odds a ios om he ela ionship be ween o e weigh and g ow h eloci y, peak eloci y and Reed 1 pa ame e s, adjus ing o sex and coho di e ence Main p edic o Model 1 Model 2 Model 3 a OR (95% CI) OR (95% CI) OR (95% CI) Sex :boys Re :gi ls 0.88 (0.49, 1.58) b Coho : BH Re LUN 0.02 (0.005, 0.09) Bi h weigh 1.25 (0.67, 2.34) b Pa ame e s (weigh ) a w 1.53 (1.19, 1.97) 1.55 (1.20, 2.02) 1.12 (0.89, 1.40) b b w 2.21 (1.65, 2.96) 2.27 (1.68, 3.08) 2.05 (1.46, 2.87) c w 1.46 (1.24, 1.72) 1.48 (1.25, 1.75) 1.08 (0.92, 1.27) b d w 1.06 (0.87, 1.29) b 1.07 (0.88, 1.31) b 1.05 (0.92, 1.21) b Pa ame e s (heigh ) a h 1.79 (1.46,2.21) 1.79 (1.45, 2.22) 0.88 (0.67, 1.15) b b h 1.71 (1.21, 2.42) 1.70 (1.20,2.41) 1.14 (0.77, 1.70) b c h 0.74 (0.62, 0.89) 0.74 (0.62, 0.89) 1.05 (0.90, 1.24) b d h 0.53 (0.43, 0.65) 0.53 (0.43, 0.65) 1.10 (0.84, 1.45) b In ancy peak eloci y PWV 1.42 (1.08, 1.87) 1.42 (1.07, 1.88) 1.68 (1.17, 2.42) PHV 1.58 (0.99, 2.52) b 1.56 (0.97, 2.50) b 1.44 (0.76, 2.74) b APWV 0.06 (0.01, 0.12) 0.03 (0.01, 0.12) 4.31 (0.78, 23.7) b APHV 0.99 (0.74, 1.35) b 0.99 (0.74, 1.34) b 1.17 (0.88, 1.55) b Weigh eloci y 3 mon hs 7.49 (4.50, 12.46) 7.96 (4.68, 13.52) 4.80 (2.49, 9.26) 6 mon hs 4.07 (2.82, 5.86) 4.09 (2.84, 5.90) 2.60 (1.77, 3.83) 12 mon hs 3.51 (2.48, 4.94) 3.58 (2.52, 5.08) 2.46 (1.89, 3.61) 24 mon hs 3.06 (2.20, 4.25) 3.18 (2.26, 4.47) 2.44 (1.68, 3.55) 48 mon hs 2.67 (1.95, 3.66) 2.78 (2.01, 3.86) 2.41 (1.68, 3.64) 60 mon hs 2.60 (1.90, 3.56) 2.71 (1.96, 3.75) 2.39 (1.65, 3.47) Heigh eloci y 3 mon hs 3.02 (2.19, 4.15) 3.01 (2.19, 4.14) 0.87 (0.50, 1.50) b 6 mon hs 5.49 (3.27, 9.22) 5.52 (3.29, 9.24) 1.62 (0.61, 4.32) b 12 mon hs 2.25 (1.60, 3.15) 2.25 (1.60, 3.16) 1.35 (0.89, 2.03) b 24 mon hs 1.55 (1.13, 2.14) 1.54 (1.12, 2.13) 1.34 (0.88, 2.04) b 48 mon hs 1.51 (1.10, 2.09) 1.50 (1.09, 2.07) 1.32 (0.86, 2.03) b 60 mon hs 1.55 (1.12, 2.14) 1.53 (1.11, 2.13) 1.26 (0.82, 1.94) b a No adjus ed o sex due o limi ed numbe o child en in Lungwena coho wi h ou come. b E ec o main p edic o was no signi ican . Model 1: O e weigh s. main p edic o . Model 2: O e weigh s. main p edic o (adjus ing o bi h weigh ). Model 3: O e weigh s. main p edic o (adjus ing o bi h weigh and coho di e ences). POSTNATAL GROWTH AND OBESITY IN EARLY ADOLESCENTS 649 Ame ican Jou nal o Human Biology o li e. This apid weigh gain was associa ed wi h a high p e alence o o e weigh adolescen s in his popula ion. The di e ences in he p e alence o o e weigh adoles- cen s in he wo coho s, conside ing he non-signi ican di e ences in hei size a bi h, highligh s he signi i- cance o apid weigh gain a he han bi h size, in he ela ionship be ween ea ly g ow h and obesi y in adoles- cence, in his pa icula se ing. These esul s a e in sup- po o he “ as g ow h and obesi y” hypo hesis, a he han he “size a bi h” o he “size a bi h and as g ow h” hypo heses. The ela ionship be ween as e g ow h eloci y and obesi y/o e weigh in la e li e, inde- penden o bi h weigh , has been hypo hesised o be mainly due o o e -nu i ion (Jones-Smi h e al., 2013). The mo e apid weigh gain in he BH coho ela i e o he Lungwena coho may be due o nu i ional and en i- onmen al di e ences, among o he ac o s. The slowe weigh eloci y in he Lungwena coho , om as ea ly as 3 mon hs, could be due o poo ma e nal nu i ional s a- us and he ea ly in oduc ion o complemen a y oods. As Lungwena is p edomina ely a poo u al communi y, he complemen a y oods used a e likely o be o poo nu i- ional con en and o expose he in an s o pa hogens (Espo e al., 2002). Ou esul s a e in gene al consis en wi h s udy by Adai e al. (2013), which also looked a associa ion be ween weigh and heigh gain, and adul heal h ou - comes in i e coho s om LMIC (Adai e al., 2013). The s udy ound a posi i e ela ionship be ween weigh gain and adul BMI, wi h he s eng h o he ela ionship inc easing wi h age a which measu emen was aken. Howe e , unlike ou s udy, hey also ound posi i e ela- ionship be ween bi h weigh and adul BMI, and hey also ound a dec easing ela ionship be ween heigh gain and BMI. The a ia ions in hese esul s could be due o he di e ences in he age anges used as well as he lim- i ed amoun o obse a ions a 3 and 6 mon hs in he BH coho o ou s udy. Apa om looking a coho s om di e en SES and en i onmen al se ings, he o he s eng h o his s udy is in he use o mixed e ec s modelling o model g ow h a- jec o ies and o de i e g ow h eloci ies. Mixed e ec s modelling allowed us o compa e g ow h eloci y a any age e en hough some o he da a collec ion wa es in he wo coho s we e a di e en imes. Ou esul s a e in gene al, consis en wi h esul s om o he s udies ha ha e used mixed e ec s. In a s udy o Du ch child en, Mook-Kanamo i e al., also using he Be key-Reed model and mixed e ec s modelling, ound ha apid weigh gain in he i s mon hs was mo e associa ed wi h isk o o e - weigh han ca ch-up g ow h (‘size a bi h and as g ow h hypo hesis’) du ing he i s 2 yea s (Mook-Kana- mo i e al., 2011). Simila ly, Bo on e al. (2008) using he adap ed Jenns-Bayley model and using mixed e ec s modelling, also ound inc eased isk o obesi y due o apid g ow h in he i s 6 mon hs in F ench child en. Howe e , hei s udy also ound ha his isk s a ed inc easing again om 3 yea s. Howe e , hey de i ed hei g ow h eloci y om a model i ed om bi h o 10 yea s, which may ha e made i possible o pick ou he inc ease in g ow h eloci y om 3 yea s. Ou s udy i ed he g ow h model up o 5 yea s only. The main limi a ion o he s udy is una ailabili y o da a on adolescen ac o s associa ed wi h BMI in one o he coho , which could ha e been adjus ed o in he ela- ionship be ween pos na al g ow h and adolescen BMI/ o e weigh . The o he limi a ion o he s udy is he amoun o missing weigh and heigh measu emen s du - ing he i s yea o li e in he BH coho which could ha e a ec ed he i ness o he g ow h model used o es ima - ing g ow h eloci y. In conclusion, al hough ou esul s suppo he hypo h- esis ha apid g ow h in in ancy inc eases he isk o o e weigh / obesi y in la e li e, he long e m e ec s o in ancy apid g ow h a e dependen on he pa icula pop- ula ion’s s age o nu i ion ansi ion. Fo a popula ion in ea ly s ages o nu i ion ansi ion o wi h poo nu i- ional s a us, apid g ow h in ea ly childhood may ha e long e m bene icial e ec s as was e idenced by he almos non-exis en p e alence o o e weigh in he Lung- wena coho , despi e some child en exhibi ing apid g ow h in ea ly childhood. Con e sely, o popula ions unde going apid nu i ion ansi ion as is he case wi h he BH coho , apid g ow h has de imen al long e m e ec s, as was e idenced by he p e alence o o e weigh and obesi y in ea ly adolescence. To u he explo e he ela ionship be ween pos na al g ow h eloci y and la e heal h ou come, we would ecommend modelling g ow h in o adolescence and also include pube al s ages and SES ac o s du ing adolescence ha a e highly associa ed wi h BMI, such as die a y pa e ns and physical ac i i y beha io s o he adolescen s in he coho s. Fu he s ud- ies in simila coho s in LMIC migh also help in explain- ing he e ec o shi s in die a y and seden a y beha io s associa ed wi h u baniza ion. LITERATURE CITED Adai L. 2007. Size a bi h and g ow h ajec o ies o young adul hood. Am J Hum Biol 19:327–337. Adai LS, Fall CH, Osmond C, S ein AD, Ma o ell R, Rami ez-Zea M, Sachde HS, Dahly DL, Bas I, No is SA, Mickles ield L, Hallal P, Vic o a CG. 2013. 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