Prevalence and incidence of cognitive impairment in an elder Portuguese population (65–85 years old)

RESEARCH ARTICLE Open Access P e alence and incidence o cogni i e impai men in an elde Po uguese popula ion (65–85 yea s old) Rica do Pais 1,2,3* , Luís Ruano 1,2,4 , Ca la Mo ei a 1,2 , O élia P. Ca alho 1,2 and Hen ique Ba os 1,2 Abs ac Backg ound: The inc ease in a e age li e expec ancy inc eases he isk o illness and ail y in he elde ly, especially in he cogni i e a ena. This s udy has he objec i e o es ima e he p e alence and incidence o cogni i e impai men , in a ep esen a i e sample o 65 o 85 yea s old ollowed o a mean pe iod o 6-yea s. Me hods: Subjec s aged 65–85 yea s (n= 586) we e sc eened a baseline (1999–2004) o es ima e he p e alence o cogni i e impai men using he Mini-Men al S a e Examina ion. A o al o 287 indi iduals wi h a no mal MMSE a baseline we e eassessed a e 6.2 mean yea s (± 4.30 yea s) o e alua e he incidence o cogni i e impai men , de ined as sco ing below he age and educa ion-adjus ed MMSE cu -o poin s adap ed o he Po uguese popula ion. We did no exclude Demen ia. Resul s: The baseline p e alence o cogni i e impai men was 15.5% (95% CI: 12.7–18.7). Highe in women (18.9%; 95% CI: 14.9–23.3), ha in men (10.4%; 95% CI: 6.7–15.1). Inc eased wi h age and was highes o pa icipan s wi hou any schooling. The o e all incidence a e was 26.97 pe 1000 pe son-yea s; highe in women (33.8 pe 1000 pe son-yea s) han in men (18.0 pe 1000 pe son-yea s). Highe o he oldes pa icipan s and hose wi h no schooling. Taking he s anda d Eu opean popula ion, we es ima ed a p e alence o 16.5% and an incidence o 34.4 pe 1000 pe son-yea s. Conclusion: The p e alence o cogni i e impai men in Po ugal is wi hin he es ima ed in e al o he Eu opean popula ion, and he incidence is lowe han o he majo i y o he Eu opean coun ies. Women, senio and elde s wi hou educa ion ha e a highe isk o cogni i e impai men . In ou sample, nei he employmen no ma i al s a us has a signi ican e ec on cogni i e impai men . Keywo ds: Cogni i e impai men , P e alence, Incidence, Popula ion-based coho , EPIPo o Backg ound The ageing o he wo ld popula ion is a demog aphic end ha will in ensi y in he coming decades. Eu os a p ojec s ha by 2050 Po ugal will be he Eu opean coun y wi h he highes pe cen age o people aged 55 yea s o mo e (47%) [1]. The g owing numbe o olde people poses heal h challenges such as inc easing he p e alence o dis- ease and disabili y in he elde s, especially he bu den o cogni i e dys unc ions [2]. Cogni i e impai men inc eases he isko demen iaandmo ali yin heelde s[3,4]. I is cha ac e ised by indi iduals ha ing mo e di icul ies wi h memo y, lea ning, and he abili y o ocus on a ask, han wouldbeno mallyexpec ed o heindi idual’sageand educa ional le el [5]. I anges om mild de ici s ha a e no clinically de ec able o demen ia [5]. I has a social im- pac and is associa ed wi h o he pa hologies, such as © The Au ho (s). 2020 Open Access This a icle is licensed unde a C ea i e Commons A ibu ion 4.0 In e na ional License, which pe mi s use, sha ing, adap a ion, dis ibu ion and ep oduc ion in any medium o o ma , as long as you gi e app op ia e c edi o he o iginal au ho (s) and he sou ce, p o ide a link o he C ea i e Commons licence, and indica e i changes we e made. The images o o he hi d pa y ma e ial in his a icle a e included in he a icle's C ea i e Commons licence, unless indica ed o he wise in a c edi line o he ma e ial. I ma e ial is no included in he a icle's C ea i e Commons licence and you in ended use is no pe mi ed by s a u o y egula ion o exceeds he pe mi ed use, you will need o ob ain pe mission di ec ly om he copy igh holde . To iew a copy o his licence, isi h p://c ea i ecommons.o g/licenses/by/4.0/. The C ea i e Commons Public Domain Dedica ion wai e (h p://c ea i ecommons.o g/publicdomain/ze o/1.0/) applies o he da a made a ailable in his a icle, unless o he wise s a ed in a c edi line o he da a. * Co espondence: pais. ica [email protected] 1 EPIUni - Ins i u o de Saúde Pública, Uni e sidade do Po o, Rua das Taipas, n° 135, 4050-600 Po o, Po ugal 2 Depa amen o de Epidemiologia Clínica, Medicina P edi i a e Saúde Pública, Faculdade de Medicina da Uni e sidade do Po o, Alameda P o . He nâni Mon ei o, 4200-319 Po o, Po ugal Full lis o au ho in o ma ion is a ailable a he end o he a icle Pais e al. BMC Ge ia ics (2020) 20:470 h ps://doi.o g/10.1186/s12877-020-01863-7 Alzheime o Demen ia [6,7]. Age, sex and le el o educa- ion a e conside ed isk ac o s o cogni i e impai men [4]. Con inued p o essional ac i i ies may be p o ec i e agains cogni i e decline [8] howe e he e is a lack o in- o ma ion abou he impac on cogni i e unc ion o pos - ponemen o e i emen age. Also, changing demog aphics cha ac e is ics added o a highe di o ce a e inc eases he numbe o olde people li ing alone, especially women, which adi ionally al eady p esen ed wi h an inc eased isk o cogni i e decline [1,9,10]. Repo s on he p e alence and incidence o cogni i e impai men , as well as i s ela ion wi h como bidi ies and sociodemog aphic ac o s, a e essen ial o public heal h and clinical ca e policy. They a e necessa y o allow p ima y and seconda y p e en ion measu es wi hin he heal hca e sys em. In Eu ope, published s udies epo he p e alence o cogni i e impai men o be be ween 5.1 and 24.5% [11– 16], whe eas in No h Ame ica, he es ima ed cogni i e impai men p e alence anges om 13.8 o 28.3% [17– 19]. In Eu ope epo s ha used he Mini-Men al S a e Exam o cogni i e impai men e alua ion in samples wi h he same age cha ac e is ics as ou s es ima ed cog- ni i e impai men p e alence be ween 7.7 and 33.1% [12,16,20]. The incidence o cogni i e impai men anges om 56.5 o 76.8 pe 1000 pe son-yea s in Eu - ope [16,20,21] and om 41.8 o 65.4 pe 1000 pe son- yea s, in No h Ame ica [22–24] In Po ugal, p e iously published s udies epo a p e alence o cogni i e im- pai men anging om 9.3 o 12.0% [10,25,26] and as a as we know, he incidence is unknown. Me hods Aim This s udy aims o es ima e he p e alence and inci- dence o cogni i e impai men a e 6.2 mean yea ’s ollow-up assessed using he Mini-Men al S a e Exam (MMSE) in a coho o ci y dwelle s om Po o, Po ugal, aged 65 o 85 yea s old, and o e alua e he im- pac o age, sex, schooling, e i emen and ci il s a us in cogni i e unc ion. Fo he main a iables o in e es , we hypo hesize ha cogni i e impai men p e alence and incidence a e simila o o he Eu opean coun ies. S udy popula ion The EPIPo o coho s udy design and me hodology ha e been published p e iously [27,28]. In b ie , be- ween 1999 and 2004, we assembled a ep esen a i e sample o communi y dwelle s o Po o, an u ban cen e in he no hwes o Po ugal, wi h app oxima ely 300, 000 inhabi an s a he ime. We selec ed Households by andom digi dialling o landline elephones. Wi hin each household, selec ed by simple andom sampling a pe manen esiden aged 18 yea s o mo e and no eplaced e usals. The p opo ion o pa icipa ion was 70%, and he inal sample size was 2485 indi iduals. O he 633 pa icipan s wi h age be ween 65 and 85 yea s old, 586 comple ed he assessmen a baseline. The ollow-up e alua ion ook place in wo wa es, pa o he pa icipan s (N= 221) we e e alua ed du ing he i s ollow-up, be ween 2005 and 2008, and he o he s we e e alua ed only on he second ollow-up (N= 66), be- ween 2013 and 2015 (Fig. 1). Da a collec ion and de ini ion o a iables T ained in e iewe s pe o med a ace- o- ace ques ion- nai e which collec ed da a on sociodemog aphic and be- ha iou al cha ac e is ics [29] and adminis e ed he Mini- Men al S a e Exam (MMSE) a he beginning o each in e iew [30]. Educa ion was eco ded as comple ed yea s o schooling and u he ca ego ized in o h ee g oups: ze o yea s, one o 9 yea s and mo e han 10 yea s o schooling. Ci il s a us was ca ego ized in wo g oups: ma ied o li ing oge he , and no -ma ied (di- o ced, single o widowed). P o essional s a us was con- side ed o be ei he wo king (pa icipan s employed), e i ed (conside ing e i emen as a di ec ansi ion be- ween a si ua ion o ull employmen and a si ua ion whe e he indi idual is en i ely inac i e and whe e mos o his esou ces consis o pension bene i s), o house- wi es. The e we e no unemployed pa icipan s. Cogni- i e impai men was e alua ed using he MMSE [30], wi h cu -o poin s adjus ed by yea s o schooling ali- da ed o he Po uguese popula ion: 22 o 0–2 yea s; 24 o 3–6 yea s and 27 o se en o mo e yea s o schooling [31]. Subjec s wi h an MMSE sco e below he age and educa ion adjus ed cu -o poin we e consid- e ed o ha e cogni i e impai men . The MMSE is he mos ci ed small-sized scale used o demen ia and cog- ni i e impai men assessmen and is hough o be a eli- able and alid es o cogni i e impai men [30,32]. P e alence e alua ion A he baseline e alua ion, 633 pa icipan s we e aged 65 o 85 yea s old, bu we excluded 47 subjec s due o miss- ing in o ma ion on he Mini-Men al S a e Exam (MMSE). The inal sub-sample was 586 pa icipan s (Table 1) wi h 71.95 yea s (± 4.84 SD) mean age; 355 we e women (60.6%); 57 (9.7%) had no educa ion, 432 (73.7%) had one o 9 yea s o educa ion, and 97 (16.6%) had mo e han 10 yea s (16.6%) o schooling; 350 (59.7%) we e ma ied o li ing in ci il union; 464 (79.2) we e e i ed. Incidence e alua ion The e we e wo ollow-up e alua ions whe e he pa ici- pan s comple ed a ques ionnai e and had a physical examina ion. The i s ollow-up was be ween 2005 and Pais e al. BMC Ge ia ics (2020) 20:470 Page 2 o 10 Fig. 1 Flow-cha o pa icipan s h ough he s eps o he s udy and inal esul s on he equency o cogni i e impai men Table 1 Socio-demog aphic cha ac e is ics o pa icipan s Cha ac e is ic Baseline Follow-up Los o ollow-up P alue N 586 287 208 Sex Female 355 (60.6) 169 (58.9) 119 (57.2) 0.709 Male 231 (39.4) 118 (41.1) 89 (42.8) Age (yea s) [65–69] 216 (36.9) 125 (43.6) 67 (32.2) 0.010* [70–74] 200 (34.1) 100 (34.8) 70 (33.7) [75–79] 120 (20.5) 46 (16.0) 50 (24.0) [80–85] 50 (8.5) 16 (5.6) 21 (10.1) Educa ion 0 57 (9.7) 17 (5.9) 14 (6.7) 0.751 [1–9] 432 (73.7) 219 (76.3) 162 (77.9) ≥10 97 (16.6) 51 (17.8) 32 (15.4) Ma i al S a us Ma ied/Ci il Union 350 (59.7) 180 (62.7) 118 (56.7) 0.179 Single, di o ced, widowe 236 (40.3) 107 (37.3) 90 (43.3) Employmen S a us Wo k 50 (8.5) 26 (9.1) 18 (8.7) 0.626 Re i ed 464 (79.2) 233 (81.2) 164 (78.8) Housewi es 71 (12.1) 28 (9.8) 26 (12.5) Legend: Da a a e n(%); P- alue compa es ollow-up o los o ollow up, ob ained wi h Chi-squa e es *Signi ican a p< 0.05 Pais e al. BMC Ge ia ics (2020) 20:470 Page 3 o 10 2008 and he second ollow-up be ween 2013 and 2015. Some pa icipan s we e e alua ed only du ing he 1s o he 2nd ollow-up. O he ini ial 586 eligible pa icipan s, he e we e o e all 208 losses wi h 103 (49.5%) dea hs, 51 (24.5%) e usals, 26 (12.5%) we e no possible o con ac and 28 (13.5%) missed wi hou jus i ica ion. We e- e alua ed a o al o 287 pa icipan s (mean ollow-up o 6.2 yea s, SD 4.30 yea s). The e we e no signi ican di - e ences ega ding sex, educa ion, ci il s a us o employ- men s a us be ween ollow up pa icipan s and hose los o ollow-up (Table 1). Howe e , pa icipan s los o ollow-up we e olde (72.58 s 71.09 mean age in yea s). Compe ing isk model Du ing he ollow-up, in he disease/dea h p ocess, o en mo e han one ype o e en plays a ole. We a e in e - es ed as he i s e en a diagnosis o cogni i e impai - men . Howe e , dea h may p e en he e en o in e es om occu ing, because he pe son died be o e he diag- nosis o cogni i e impai men . The e o e, dea h is a compe ing isk o cogni i e impai men and may sub- s an ially change he isk o disease diagnosis. Dea h subs an ially educes he p obabili y o being diagnosed wi h cogni i e impai men , and hence is ea ed as a compe ing isk e en when calcula ing cogni i e impai - men incidence [33,34]. Igno ing dea h as a compe ing isk o ea i as no in o ma i e censo ed obse a ions will lead o a bias in he s anda d me hods o es ima e he p obabili y o he e en [35] such as he Kaplan- Meie es ima e [36]. The assump ion o independence o he ime o e en and he censo ing dis ibu ions is io- la ed and hen iola es one o he undamen al assump- ions o he Kaplan-Meie es ima o . We conside ed he ime o e en as he ime om en e ing in he coho o he i s e en , cogni i e impai men o dea h, du ing he ollow-up. The cumula i e incidence unc ion (CIF) allows o es- ima ion o he incidence o he occu ence o an e en while aking compe ing isk in o accoun [37,38]. This allows one o es ima e incidence in a popula ion whe e all compe ing e en s mus be accoun ed o in clinical decision making. I deno es he p obabili y o expe ien- cing he k h e en be o e ime and be o e he occu - ence o a di e en ype o e en , i.e., o ins ance, he p obabili y o expe ience dea h be o e 70 yea s old, be- o e he occu ence o he cogni i e impai men . The CIF has he desi able p ope y ha he sum o he CIF es ima es o he incidence o each o he indi idual ou - comes will equal he CIF es ima es o he incidence o he composi e ou come consis ing o all o he compe - ing e en s [39]. We pe o med he compe ing isks analysis o he 495 pa icipan s a isk o incidence o cogni i e impai men , excluding hose 105 ha e used o pa icipa e, missed o we e impossible o con ac along all pe iod o he ollow-up. F om hese 390, 103 died be o e cogni i e im- pai men diagnosis, 48 we e diagnosed wi h cogni i e impai men and 239 we e s ill ali e wi hou cogni i e impai men diagnosis. S a is ical analysis We assessed di e ences in he p eposi ions using he Chi-Squa e es . Losses o ollow-up we e compa ed o pa icipan s in he ollow-up using he Chi-Squa e es . Calcula ed c ude inciden a es di iding he numbe o e en s by o al numbe o pe son-yea s a isk. Coun ed ime a isk as he ime in yea s be ween he baseline e alua ion and he las ollow-up ha each pa icipan a ended and aking in o conside a ion he ull leng h o ime o subjec s who emained ee o cogni i e impai - men , and es ima e ime o onse o cogni i e impai - men being se o he midpoin be ween he baseline and ollow-up obse a ion wa es o hose pa icipan s who did de elop he disease. Poisson gene alized linea models we e used o de e mine con idence in e als, wi h Log o ime a isk as o he o se . We es ed he possible in e ac ion o each explana o y a iable wi h age, sex, educa ion and e i emen s a us was es ed. Sex-, age-, educa ion- and educa ion- adjus ed OR and RR we e es ima ed. S anda dized p e alen and inciden a es we e calcula ed o he Po uguese popula ion using da a om he las census, in 2011 [40], and o Eu opean popula ion using da a om he s anda d Eu o- pean popula ion, 2013 [41]. The CIFs we e es ima ed in R using he cuminc unc ion in he cmp sk R[42] pack- age which uses he cumula i e incidence unc ion in o- duced by Kalb leisch and P en ice [38].We used he G ay’s es [43] o equali y o CIFs ac oss g oups. We assessed di e ences in he MMSE mean sco e educ ion o pa icipan s wi h and wi hou cogni i e impai men wi h T- es o independen samples. The emaining s a is ical analyses we e pe o med using SPSS® e sion 21. We include he Box Plo o he Mini-Men al S a e Examina ion sco e o he popula ion a baseline e alu- a ion and o he pa icipan s wi h o wi hou cogni i e impai men a he ollow-up e alua ion as Supplemen- a y ma e ial (Figu e S1). Resul s P e alence e alua ion The c ude p e alence o cogni i e impai men was 15.5% (95% CI: 12.7–18.7) a baseline. The s anda dized p e alence a e o he Po uguese popula ion was 16.9% and o he s anda d Eu opean popula ion was 16.5%. P e alence was lowe in men (10.4%; 95% CI: 6.7–15.1) han in women (18.9; 95% CI: 14.9–23.3), wi h he odds o p esen ing cogni i e impai men , adjus ed o age and educa ion, o 0.95 (95% CI: 0.89–1.01). Pais e al. BMC Ge ia ics (2020) 20:470 Page 4 o 10 The p e alence o cogni i e impai men inc eases wi h age, being highe a 80–85 yea s han 65–69 yea s (26.0; 95% CI: 17.3–40.2 s 11.1; 95% CI: 9.3–17.2), wi h he odds o cogni i e impai men , adjus ed o sex and edu- ca ion, being 1.14 highe . The cogni i e impai men p e alence is highe o pa - icipan s wi h ze o yea s o schooling (45.6; 95% CI: 32.4–59.3) and sligh ly highe o pa icipan s wi h mo e han 10 yea s han o pa icipan s wi h one o 9 yea s (14.4; 95% CI 8.1–23.0 s 11.8; 95% CI 8.9–15.2) wi h s a is ically signi ican di e ences. No -ma ied pa icipan s had a highe p e alence o cogni i e impai men (16.5; 95% CI: 12.0–21.9 s 14.9; 95% CI: 11.3–19.0), bu he di e ence was no s a is i- cally signi ican a e adjus men o age and educa ion. Re i ed pa icipan s had a highe p e alence o cogni i e impai men han he wo king pa icipan s (14.4; 95% CI: 11.4–18.0 s 12.0; 95% CI: 4.6–24.3) and housewi es ha e he highes p e alence (23.9; 95% CI: 14.6–35.5) bu wi h- ou s a is ically signi ican di e ences. (Table 2). Incidence e alua ion Du ing he s udy p o ocol, 48 indi iduals de eloped cog- ni i e impai men , an incidence a e o 26.97 pe 1000 pe son-yea s (95% CI: 20.3–35.8). The s anda dized inci- dence a e using he Po uguese popula ion was 35.7 pe 1000 pe son-yea s and using he s anda d Eu opean popula ion was 34.4 pe 1000 pe son-yea s. The incidence o cogni i e impai men was highe in women (33.8 pe 1000 pe son-yea s; 95% CI: 24.2–47.4) han men (18.0 pe 1000 pe son-yea s; 95% CI: 10.7–30.5) and inc easing wi h age a 80–85 yea s old (66.0 pe 1000 pe son-yea s; 95% CI: 27.5–158.7) s 65–69 yea s old (21.1 pe 1000 pe son-yea s; 95% CI: 13.5–33.1). As obse ed on baseline p e alence, he incidence is highe o pa icipan s wi h ze o yea s o schooling (126.4; 95% CI: 68.0–234.8) and almos he same o pa - icipan s wi h 1 o 9 yea s and mo e han 10 yea s (21.6; 95% CI: 15.0–31.0 s 25.3; 95% CI 13.2–48.7). No ma ied pa icipan s ha e a highe incidence a e o cogni i e impai men (32.5; 95% CI: 21.4–49.4 s 23.6; 95% CI: 16.1–34.6), bu he di e ence did no e- eal s a is ically signi ican di e ences a e adjus ing o age and educa ion. Re i ed pa icipan s ha e a highe incidence o cogni- i e impai men han wo king pa icipan s (30.0; 95% CI: 21.3–37.9 s 18.1; 95% CI: 6.8–48.3) bu wi hou s a is i- cally signi ican di e ences. (Table 3). Table 2 Obse ed p e alence o cogni i e impai men by socio-demog aphic cha ac e is ics Cha ac e is ics n P e . % (95% CI) p- alue OR (95% CI) Adjus ed Sex Female 67 18.9 (14.9–23.3) 0.006* 1 [ e e ence] a Male 24 10.4 (6.7–15.1) 0.95 (0.89–1.01) Age (yea s) [65–69] 24 11.1 (9.3–17.2) 0.026* 1 [ e e ence] b [70–74] 30 15.0 (11.0–21.1) 1.03 (0.97–1.10) [75–79] 24 20.0 (13.3–28.3) 1.10 (1.02–1.19) [80–85] 13 26.0 (17.3–40.2) 1.14 (1.03–1.27) Educa ion 0 26 45.6 (32.4–59.3) 0.000* 1 [ e e ence] c [1–9] 51 11.8 (8.9–15.2) 0.72 (0.66–0.80) ≥10 14 14.4 (8.1–23.0) 0.74 (0.67–0.84) Ma i al S a us Ma ied/Ci il Union 52 14.9 (11.3–19.0) 0.584 1 [ e e ence] d Single, di o ced, widowe 39 16.5 (12.0–21.9) 0.96 (0.90–1.02) Employmen S a us Wo k 6 12.0 (4.6–24.3) 0.471 1 [ e e ence] a Re i ed 67 14.4 (11.4–18.0) 99.6 (0.90–1.10) Housewi es 17 23.9 (14.6–35.5) 1.07 (0.94–1.22) Legend: P e P e alence, OR odds a io. 95% CI: 95% con idence in e al a adjus ed o age and educa ion b adjus ed o sex and educa ion c adjus ed o sex and age d adjus ed o sex, age and educa ion * Signi ican a p< 0.05 Pais e al. BMC Ge ia ics (2020) 20:470 Page 5 o 10 The c ude cumula i e incidences o cogni i e impai - men and dea h in he o e all sample a e desc ibed in Fig. 2, along wi h he incidence o he composi e ou - come o all-cause o ailu e (dea h o cogni i e impai - men ). The cumula i e incidence o all-cause ailu e is equal o he sum o he cumula i e incidences o he 2 cause-speci ic ailu es. Al hough he cumula i e inci- dence o dea h be o e he cogni i e impai men exceeded ha o cogni i e impai men diagnosis a each poin in ime, he incidence o cogni i e impai men was no negligible in his popula ion. In he g oup analysis by sex, he cumula i e incidence cu es o women and men we e s a is ically di e en o cogni i e impai men be o e dea h (P- alue 0.0008), and o dea h be o e cog- ni i e impai men (P- alue 0.0004). The es ima ed CIFs o each cause o ailu e by sex displayed in Fig. 3p e- sen ed no able di e ences. In women, om 73 yea s old o 80 yea s old, he cumula i e incidence o cogni i e impai men is highe ha i s compe i i e e en , while o he men, he incidence o dea h be o e cogni i e im- pai men is highe in all poin s in ime when compa ed o he cogni i e impai men diagnosis, ollowing he same end as when analysing he whole sample. The es- ima es o dea h be o e cogni i e impai men diagnosis Fig. 2 Cumula i e incidence unc ions. The solid line shows he cumula i e incidence o cogni i e impai men . The do ed line shows he compe ing isk e en , i.e. dea h occu ing p io o he cogni i e impai men . The dashed line shows he cumula i e incidence unc ion o all-cause ailu e, i.e. he sum o he cumula i e incidences o he 2 cause-speci ic ailu es Table 3 Obse ed incidence o cogni i e impai men by socio-demog aphic cha ac e is ics Cha ac e is ics n Incidence (95% CI) pe 1000 pe son-yea s p- alue RR (95% CI) Adjus ed Sex Female 34 33.8 (24.2–47.4) 0.084 1 [ e e ence] a Male 14 18.0 (10.7–30.5) 0.66 (0.35–1.27) Age (yea s) [65–69] 19 21.1 (13.5–33.1) 0.142 1 [ e e ence] b [70–74] 16 25.8 (15.8–42.2) 1.29 (0.66–2.52) [75–79] 8 43.5 (21.7–86.9) 2.20 (0.96–5.05) [80–85] 5 66.0 (27.5–158.7) 2.01 (0.72–5.58) Educa ion 0 10 126.4 (68.0–234.8) 0.005* 1 [ e e ence] c [1–9] 29 21.6 (15.0–31.0) 0.21 (0.10–0.47) ≥10 9 25.3 (13.2–48.7) 0.25 (0.10–0.65) Ma i al S a us Ma ied/Ci il Union 26 23.6 (16.1–34.6) 0.296 1 [ e e ence] d Single, di o ced, widowe 22 32.5 (21.4–49.4) 1.03 (0.55–1.93) Employmen S a us Wo k 4 18.1 (6.8–48.3) 0.911 1 [ e e ence] a Re i ed 40 30.0 (21.3–37.9) 1.30 (0.44–3.79) Housewi es 4 22.3 (24.2–47.4) 0.79 (0.19–3.31) Legend: RR ela i e isk. 95%, CI 95% con idence in e al a adjus ed o age and educa ion b adjus ed o educa ion and sex c adjus ed o age and sex d adjus ed o sex, age and educa ion *Signi ican a p< 0.05 Pais e al. BMC Ge ia ics (2020) 20:470 Page 6 o 10 o he women exceeds he es ima es o cogni i e impai - men diagnosis in he poin ’s ime a e 80 yea s old. The slope o he cu es a e qui e simila in women and men un il 70 yea s −75 yea s old, howe e , in he men i can be obse ed a highe p obabili y o dea h be o e cogni- i e impai men han in he women. Pa icipan s wi h cogni i e impai men had an a e age MMSE sco e educ ion o 5.33 (SD 3.64), while pa ici- pan s wi hou cogni i e impai men had an a e age o 0.44 educ ion (SD = 1.84) (p= 0.000) o e he ime a isk o 6.2 mean yea s (± 4.30 yea s). Discussion In his u ban popula ion wi h 65 o 85 yea s, he p e a- lence o cogni i e impai men was 15.5%. I was highe in women, in no -ma ied pa icipan s, and e i ed pa - icipan s, i inc eased wi h age and dec eased wi h edu- ca ion yea s. P e ious s udies wi h Po uguese popula ion samples e- po ed a p e alence o cogni i e impai men be ween 9.3 and 12.0% [10,25,26] using younge pa icipan s, o e 50 yea s old on he i s s udy and o e 55 yea s old on he o he wo. Bo h he s udies which used he MMSE as a sc eening es , Nunes e al. [25] and Ruano e al. [26]com- plemen ed he esul s wi h a neu ologis e alua ion. I is wo h o poin ou ha Ruano e al. [26] epo he 2015 p e alence o he EpiPo o coho wi h he p esen s udy ocusing on he pe iod om 1999 o 2004 and ha only in he cu en s udy was he incidence o cogni i e impai - men in his popula ion asce ained (1999–2015). The p e alence es ima e ound in ou s udy is wi hin he es ima ed in e al o he Eu opean popula ion using asce ainmen app oaches simila o ou s [9,20]. As p e iously epo ed cogni i e impai men p e alence was highe in women han in men [9,10,44], wi h s udies poin ing ou ho monal causes, namely he loss o es o- gens in women, o jus i y his di e ence [45]. I inc eased in equency wi h inc easing age be ween he ages o 65 and 85 yea s, which is in acco dance o o he s udies ha associa ed ageing wi h cogni i e decline and demen ia [9, 10,44,46] and i is associa ed wi h low le els o educa ion, possibly due o he highe cogni i e ese e o he ones wi h mo e yea s o educa ion [9,44,47]. Pa icipan s wi h- ou schooling ha e a highe p e alence o cogni i e im- pai men han pa icipan s wi h a leas some schooling. Pa icipan s wi h mo e han 10 yea s o schooling ha e a highe p e alence o cogni i e impai men compa ed wi h hose be ween one and 9 yea s o schooling. Howe e , his may be a ibu able o hei highe mean age and p esence o mo e pa icipan s wi h 80–85 yea s old (13.4% s 6.9%). When we de e mined he odds a io, adjus ed o sex and age, he isk is almos he same (0.72 s 0.74) be ween bo h g oups and s a is ically di e en o he g oup wi h- ou any schooling. I was also sligh ly highe o no - ma ied pa icipan s [9,44,48] despi e no eaching s a is- ical signi icance and we did no ind di e ences be ween e i ed and non- e i ed pa icipan s (Table 2). Fo 6.2 mean yea s o ollow-up ime, we obse ed ha he incidence a e o cogni i e impai men was 26.97 pe 1000 pe son-yea s. The s anda dized inciden a e o he Po uguese popula ion was 35.7 and o he s anda d Eu opean popula ion was 34.4 pe 1000 pe son-yea s. The cogni i e impai men incidence we ound in ou sample is lowe han es ima es o o he Eu opean coun- ies [20,21,49] and No h Ame ica, [22,23] howe e his migh be due o he olde popula ions and di e en cogni i e impai men de ini ions used in hese s udies. Fig. 3 Cumula i e incidence unc ions by sex. Le panel: The solid line shows he cumula i e incidence o cogni i e impai men , o women. Righ panel: The do ed line shows he compe ing isk e en , i.e. dea h occu ing p io o he cogni i e impai men , o Men Pais e al. BMC Ge ia ics (2020) 20:470 Page 7 o 10 In conco dance wi h o he s udies [22,24,49,50], we also obse ed a end owa ds inc eased incidence wi h olde age, and highe in women albei wi hou eaching s a is ical signi icance. These indings we e also achie ed when conside ing dea h as a compe ing isk o cogni i e impai men . Pa icipan s wi h ze o yea s o schooling ha e a highe incidence o cogni i e impai men han he ones wi h schooling, which is in conco dance o he impac o edu- ca ion yea s epo ed in p e ious indings [20,51]. Non-ma ied pa icipan s ha e a non-signi ican end owa ds a highe incidence o cogni i e impai men , which could be explained by he memo y and cogni ion s imula ion o he ma ied pa icipan s [52].. Fo em- ploymen s a us, we obse e ha e i ed pa icipan s ha e a end owa ds a highe incidence o cogni i e im- pai men han he ones which a e s ill wo king, a e adjus ing o age and educa ion, which may indica e a p o ec i e e ec o wo king, as desc ibed be o e [8,53]. I would be in e es ing o conduc u he wo k o y o de e mine i indeed wo king has a p o ec i e e ec on cogni i e decline o i o he social dimensions in ol ed in being employed media es his e ec . The a e age MMSE sco e educ ion is highe in pa - icipan s wi h cogni i e impai men compa ed wi h o he pa icipan s, which demons a es a mo e p o- nounced cogni i e loss on he i s ones ha mus be aken in o accoun when de ining p e en i e measu es in he Heal h Sys em. A p e ious s udy [26] has ound ha one o he majo causes o cogni i e impai men in his popula ion s ems om ascula disease, as such we sugges ha help man- aging blood p essu e and an inc ease in physical ac i i y, i a ge ed o hese g oups, could lead o signi ican pub- lic heal h imp o emen s. In Po ugal, in he pe iod unde analysis, om 1999 o 2015, he demog aphic cha ac e is ics o he popula ion o e 65 yea s old changed and, acco ding o PORDATA, he pe cen age o olde people inc eased om 15.9 o 20.5% [54], and he numbe o people wi hou educa ion dec eased by 36.7% and hose wi h highe educa ion, in- c eased by 247.7% [55]. The inc eased educa ion may ha e con ibu ed o he dec ease in he p e alence o cogni i e impai men om 15.5 o 9.3% [26], despi e some me hodological di e ences in he wo s udies in he EpiPo o coho discussed abo e. The inc ease in schooling will mi iga e he e ec o inc easing a e age li e expec ancy, bu i should be aken o he measu es because by 2050, Po ugal will be one o he Eu opean coun ies wi h a highe pe cen age o olde people and wi h he highes old-age dependency a io. The main s eng hs o ou s udy a e he popula ion- based coho and he long- e m p ospec i e s udy design as well as he use o MMSE published cu -o poin s adjus ed o educa ion. This s udy p o ides an es ima e o he p e alence and incidence o cogni i e impai men in an elde wes e n Eu opean coho p o iding essen ial da a o a ge public heal h s a egies accu a ely. Some me hodological limi a ions may ha e o e es ima ed he esul s, namely he inabili y o diagnose demen ia, meaning ha we could no exclude pa icipan s wi h de- men ia om he s udy, which may ha e o e es ima ed he p e alence o cogni i e impai men a baseline. Mo ali y as a compe ing isk may ha e o e es ima ed he incidence o cogni i e impai men . Pa icipan s los - o- ollow-up whe e olde and wi h lowe mean MMSE sco es han he pa ici- pan s and his could ha e unde es ima ed he incidence calcula ions. Conclusion This s udy epo s a p e alence o cogni i e impai men o 15.5% and an incidence o 26.97 pe 1000 pe son- yea s in a coho o ci y dwelle s om Po o, Po ugal, aged 65 o 85 yea s old. Women and elde s wi hou schooling ha e a highe isk o de eloping cogni i e im- pai men , and his isk inc eases wi h ageing. This s udy highligh s he need o de elop p e en i e heal h mea- su es a ge ed o hese g oups o help main ain b ain heal h wi h ageing. In ou s udy we ound ha nei he e i emen no ma i al s a us ha e a signi ican e ec on cogni i e impai men . Supplemen a y In o ma ion The online e sion con ains supplemen a y ma e ial a ailable a h ps://doi. o g/10.1186/s12877-020-01863-7. Addi ional ile 1: Figu e S1. Box Plo o he Mini-Men al S a e Examin- a ion sco e o he popula ion a baseline e alua ion and pa icipan s wi h o wi hou cogni i e impai men a he ollow-up e alua ion. Abb e ia ions MMSE: Mini-Men al S a e Examina ion; CIF: Cumula i e incidence unc ion; OR: Odds a io; RR: Rela i e Risk Acknowledgemen s No applicable. Au ho s’con ibu ions All au ho s con ibu ed o he s udy concep ion and design. Ma e ial p epa a ion and da a collec ion: RP. S a is ical analysis: RP, CM. W i ing - e iew and edi ing: RP, LR, CM, OC, HB. Supe ision: HB. RP w o e he i s d a o he manusc ip and all au ho s commen ed on p e ious e sions o he manusc ip . All au ho s ead and app o ed he inal manusc ip . Funding Fundo Eu opeu de Desen ol imen o Regional (FEDER), and he P og ama Ope acional Compe i i idade e In e nacionalização (POCI) (POCI-01-0145- FEDER-016867) o he Eu opean Union, and by he Fundação pa a a Ciência e a Tecnologia, no âmbi o da Unidade de In es igação em Epidemiologia - Ins i u o de Saúde Pública da Uni e sidade do Po o (EPIUni ) (POCI-01-0145- FEDER-006862; Re .° FCT UID/DTP/04750/2013). The ole o unding body was o unding EpiPo o Coho S udy. Pais e al. BMC Ge ia ics (2020) 20:470 Page 8 o 10 A ailabili y o da a and ma e ials The da ase s used and analysed du ing he cu en s udy a e a ailable om he co esponding au ho on easonable eques . E hics app o al and consen o pa icipa e All p ocedu es pe o med in s udies in ol ing human pa icipan s we e in ag eemen wi h he e hical s anda ds o he ins i u ional and na ional esea ch commi ee and wi h he 1964 Helsinki decla a ion and i s la e amendmen s o compa able e hical s anda ds. The e hics commi ee o Hospi al de São João app o ed he s udy. All indi idual pa icipan s ecei ed an explana ion on he pu pose and design o he s udy and ga e hei w i en in o med consen in he e alua ion. In pa icipan s wi h cogni i e impai men , w i en consen was also sough om a alid su oga e. Consen o publica ion No Applicable. Compe ing in e es s The au ho s decla e ha hey ha e no compe ing o in e es and ce i y esponsibili y o he manusc ip . Au ho de ails 1 EPIUni - Ins i u o de Saúde Pública, Uni e sidade do Po o, Rua das Taipas, n° 135, 4050-600 Po o, Po ugal. 2 Depa amen o de Epidemiologia Clínica, Medicina P edi i a e Saúde Pública, Faculdade de Medicina da Uni e sidade do Po o, Alameda P o . 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