ORIGINAL ARTICLE EPIDEMIOLOGY AND GENETICS
Quan i y and di e si y o en i onmen al mic obial
exposu e and de elopmen o as hma: a bi h coho s udy
A. M. Ka onen
1
, A. Hy €
a inen
1
, H. Rin ala
1
, M. Ko ppi
2
,M.T
€
aubel
1
, G. Doekes
3
, U. Geh ing
3
,
H. Renz
4
, P. I. P e e le
4
, J. Genunei
5
, L. Keski-Nisula
1,6
, S. Remes
7
, J. Lampi
1,8
, E. on Mu ius
9
&
J. Pekkanen
1,8
1
Depa men o En i onmen al Heal h, Na ional Ins i u e o Heal h and Wel a e, Kuopio;
2
Pedia ic Resea ch Cen e , Uni e si y o Tampe e
and Uni e si y Hospi al, Tampe e, Finland;
3
Ins i u e o Risk Assessmen Sciences, U ech Uni e si y, U ech , he Ne he lands;
4
Ins i u e
o Labo a o y Medicine and Pa hobiochemis y, Molecula Diagnos ics, Philipps-Uni e si y Ma bu g, Ma bu g;
5
Ins i u e o Epidemiology and
Medical Biome y, Ulm Uni e si y, Ulm, Ge many;
6
Depa men s o Obs e ics and Gynecology, Kuopio Uni e si y Hospi al;
7
Depa men o
Pedia ics, Kuopio Uni e si y Hospi al;
8
Uni o Public Heal h and Clinical Nu i ion, Uni e si y o Eas e n Finland, Kuopio, Finland;
9
Child en’s
Hospi al, Uni e si y o Munich, Munich, Ge many
To ci e his a icle: Ka onen AM, Hy €
a inen A, Rin ala H, Ko ppi M, T€
aubel M, Doekes G, Geh ing U, Renz H, P e e le PI, Genunei J, Keski-Nisula L, Remes
S, Lampi J, on Mu ius E, Pekkanen J. Quan i y and di e si y o en i onmen al mic obial exposu e and de elopmen o as hma: a bi h coho s udy. Alle gy 2014;
69: 1092–1101.
Keywo ds
as hma; a opy; child en; mic obial exposu e;
espi a o y ac disease.
Co espondence
Anne M. Ka onen, Depa men o
En i onmen al Heal h, Na ional Ins i u e o
Heal h and Wel a e, P.O. Box 95, FIN-70701
Kuopio, Finland.
Tel.: +358 (0) 29 524 6325
Fax: +358 (0) 29 524 6498
E-mail: [email p o ec ed]
Accep ed o publica ion 27 Ap il 2014
DOI:10.1111/all.12439
Edi ed by: Douglas Robinson
Abs ac
Backg ound: Ea ly-li e exposu e o en i onmen al mic obial agen s may be asso-
cia ed wi h he de elopmen o alle gies. The aim o he s udy was o iden i y be -
e ways o cha ac e ize mic obial exposu e as a p edic o o espi a o y
symp oms and alle gies.
Me hods: A bi h coho o 410 child en was ollowed up un il 6 yea s o age.
Bac e ial endo oxin, 3-hyd oxy a y acids, N-ace yl-mu amic acid, ungal ex a-
cellula polysaccha ides (EPS) om Penicillium and Aspe gillus spp., b-D-glucan,
e gos e ol, and bac e ial o ungal quan i a i e polyme ase chain eac ions
(qPCRs) we e analyzed om dus samples collec ed a 2 mon hs o age. As hma,
wheezing, cough, and a opic de ma i is we e assessed using epea ed ques ion-
nai es. Speci ic IgEs we e de e mined a he age o 1 and 6 yea s.
Resul s: Only ew associa ions we e ound be ween single mic obial ma ke s and
he s udied ou comes. In con as , a sco e o he o al quan i y o mic obial expo-
su e, ha is, sum o indica o s o ungi (e gos e ol), G am-posi i e (mu amic
acid) bac e ia, and G am-nega i e (endo oxin) bac e ia, was signi ican ly
(in e ed-U shape) associa ed wi h as hma incidence (P<0.001): he highes isk
was ound a medium le els (adjus ed odds a io (aOR) 2.24, 95% con idence
in e al (95% CI) 0.87–5.75 o 3 d quin ile) and he lowes isk a he highes
le el (aOR 0.34, 95% CI 0.09–1.36 o 5 h quin ile). The mic obial di e si y sco e,
ha is, sum o de ec ed qPCRs, was in e sely associa ed wi h isk o wheezing
and was signi ican ly (in e ed-U shape) associa ed wi h sensi iza ion o inhalan
alle gens.
Conclusion: Sco e o quan i y o mic obial exposu e p edic ed as hma be e
han single mic obial ma ke s independen ly o mic obial di e si y and amoun o
dus . Be e indica o s o o al quan i y and di e si y o mic obial exposu e a e
needed in s udies on he de elopmen o as hma.
Mic obial exposu e may con ibu e o he de elopmen o
alle gic diseases, bu he ole o di e en agen s and mecha-
nisms a e s ill unknown (1). Mos epidemiological s udies
wi h mic obial exposu e assessmen among child en ha e
been es ic ed o s udies on endo oxin (2) o ha e used only
a limi ed se o mic obial ma ke s (3–7). These mic obial
ma ke s e lec ypically only a na ow pa o he o al
mic obial exposu e. Recen ly, some s udies ha e applied
combined indica o s o mic obial exposu e (8, 9), like di e -
si y o mic obes, which appea s o ha e a p o ec i e e ec on
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d.1092
This is an open access a icle unde he e ms o he C ea i e Commons A ibu ion-NonComme cial 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 and is no used o comme cial pu poses.
he de elopmen o as hma (8). Thus, he e is a clea need o
use combined indica o s and o he new app oaches o
desc ibe exposu e o en i onmen al mic obes.
The objec i e o his s udy was he e o e o s udy p ospec-
i ely he associa ions be ween se e al ma ke s o en i onmen-
al mic obial exposu e—including hei combina ions—and
he de elopmen o doc o -diagnosed as hma, espi a o y
symp oms, a opic de ma i is, and sensi iza ion up o he age o
6 yea s.
Me hods
The s udy popula ion consis ed o child en bo n in Eas e n
and Middle Finland: he i s hal o he s udy popula ion
(N=214) belongs o a Eu opean bi h coho (PASTURE)
(10) among a me s and non a me s, while he second hal o
he coho is an ex ension o unselec ed child en (N=228)
(11). P egnan women we e ec ui ed, whose child en we e
bo n be ween Sep embe 2002 and May 2005. The s udy p o-
ocol was app o ed by a local e hics commi ee in Finland
(11). A w i en in o med consen was ob ained om he
pa en s.
Follow-up
The i s ques ionnai e was adminis e ed du ing he hi d
imes e o p egnancy (11). The ollow-up ques ionnai es
(a he age o 2, 12, 18, and 24 mon hs, and he ea e
annually), excep he ques ionnai e a 2 mon hs, enqui ed
abou any wheezing, o he espi a o y symp oms apa om
cold (wheezing, cough, noc u nal cough), and con ounde s
o he ime pe iod a e he p eceding ques ionnai e.
‘As hma e e ’ was de ined as i s pa en - epo ed doc o -
diagnosed as hma and/o second diagnoses o as hma ic (o
obs uc i e) b onchi is. ‘Cu en as hma’ was de ined as
hose as hma e e cases who also epo ed he use o
as hma medica ion and/o wheezing in pas 12 mon hs in
he 6-yea ollow-up. ‘A opic de ma i is e e ’ was de ined as
i s pa en - epo ed doc o -diagnosed a opic de ma i is du -
ing he ollow-up.
House dus samples
The p o ocols o dus collec ion a e explained in de ail in
he Supplemen a y ma e ial. B ie ly, in he Finnish PAS-
TURE s udy, ieldwo ke s ook wo samples om li ing
oom loo s o he p esen epo . The i s samples we e
p ocessed wi hou sie ing a U ech Uni e si y, whe e hey
we e ex ac ed and analyzed o endo oxin (as a ma ke o
G am-nega i e bac e ia) and EPS as desc ibed p e iously
(12), and he s o ed esidue a e ex ac ion was la e ana-
lyzed o b(1,3)-glucans (as a ma ke o ungal biomass) by
hea ex ac ion and inhibi ion enzyme immunoassay (EIA)
(13). The second samples we e p ocessed and analyzed a
Na ional Ins i u e o Heal h and Wel a e (THL), whe e hey
we e sie ed o emo e la ge pa icles, d ied, spli and hen
s o ed, and inally analyzed o mu amic acid (as a ma ke o
G am-posi i e bac e ia), e gos e ol (as a ma ke o ungal
biomass), and lipopolysaccha ide (LPS
10:0–16:0
) (as a ma ke
o G am-nega i e bac e ia) by gas ch oma og aphy andem
mass spec ome y (GC-MS–MS) (14) and by quan i a i e
polyme ase chain eac ion (qPCR) o mic obial DNA
(15–17).
In he ex ended coho , esul s om only one dus sample
om he li ing oom loo collec ed by he amilies a e used
in he p esen epo . The sample was sie ed and d ied a
THL, hen spli in aliquo s o a ious analyses: One aliquo
was sen o U ech whe e i was ex ac ed and analyzed o
endo oxin, EPS, and b(1,3)-glucans (13), and o he aliquo s
we e analyzed o he chemical ma ke s (mu amic acid,
e gos e ol, LPS
10:0–16:0
) (14) and mic obial DNA (15–17).
Quan i a i e polyme ase chain eac ion (qPCR) (15–17)
was used o de e mine mic obes ha ha e been sugges ed o
be common in mois u e-damaged buildings: wo gene a o
G am-posi i e bac e ia, Mycobac e ium spp. and S ep omy-
ces spp., and six ungal species, gene a, o g oups: he assay
g oup o Aspe gillus umiga us/Neosa o ya ische i (AspNeo
g oup); Cladospo ium spp.; he combined assay g oup o
Penicillium spp., Aspe gillus spp., and Paecilomyces a io ii
(PenAsp g oup); S achybo ys cha a um; T ichode ma i ide/
a o i ide/koningii (T ichode ma i ide g oup); and Wallemia
sebi.
Exposu e o all ma ke s was exp essed as loads, ha is, he
amoun pe m
2
sampling su ace. As he labo a o y p oce-
du es de e mine concen a ions (agen s pe mg dus ), loads
a e calcula ed by mul iplying he concen a ions wi h he mea-
su ed dus weigh pe m
2
. Howe e , as endo oxin, EPS, and
glucans in he PASTURE samples we e de e mined in nonsi-
e ed dus , while all o he analyses we e pe o med wi h sie ed
dus , we calcula ed loads o he o me pa ame e s by mul i-
plying wi h he load o sie ed dus in he pa allel sample aken
o he o he analyses. Weigh s o hese pa allel sie ed and
nonsie ed dus samples in he Finnish PASTURE s udy
showed a ai co ela ion (Spea man =0.7), bu wi h a sys-
ema ic di e ence: as expec ed, sie ed dus samples con ained
on a e age 60% (95% CI 57, 64) less dus . Mean concen a-
ions in sie ed and nonsie ed dus om non a m homes we e,
howe e , e y simila , which sugges s ha endo oxin, EPS, o
glucans a e no p e e en ially bound o he smalle (sie ed) o
la ge ( emo ed by sie ing) pa icle ac ions.
Abb e ia ions
EPS, ungal ex acellula polysaccha ide an igens o Penicillium and Aspe gillus species; GC-MS–MS, gas ch oma og aphy andem mass
spec ome y; LPS, lipopolysaccha ide; LPS
10:0-:16:0:0
, amoun (mol) o LPS in each sample. The numbe o mol o 3-hyd oxy a y acids o
C
10:0
o C
16:0
ca bon chain leng h di ided by 4; qPCR, quan i a i e polyme ase chain eac ion; PASTURE, P o ec ion agains Alle gy STUdy in
Ru al En i onmen s; OR, odds a io; aOR, adjus ed odds a io; sIgE, speci ic immunoglobulin E; kU/L, kilo uni s pe li e ; GEE, gene al
es ima ing equa ions; EIA, inhibi ion enzyme immunoassay.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d. 1093
Ka onen e al. En i onmen al mic obial exposu e and as hma
Blood sampling
Venous blood samples collec ed a one (N=374) and a
6 yea s o age (N=304) we e analyzed o speci ic immuno-
globulin E (sIgE) o 13 inhalan (De ma ophagoides p e onys-
sinus, D. a inae, alde , bi ch, Eu opean hazel, g ass pollen
mix u e, ye, mugwo , plan ain, ca , ho se and dog dande ,
and Al e na ia al e na a) and 6 ood alle gens (hen’s egg,
cow’s milk, peanu , hazelnu , ca o , and whea ) (Mediwiss
Analy ic, Moe s, Ge many) (18). The cu o le els o sIgE
concen a ions we e 0.35 kU/l a one and 0.70 kU/l a
6 yea s o age. The highe cu o was used a he age o
6 yea s due o high p e alence o sensi iza ion (Table 1).
S a is ical analyses
Gene alized es ima ing equa ions (GEE) wi h an exchange-
able co ela ion s uc u e o accoun o co ela ion be ween
epea ed measu es wi hin subjec s we e used o de e mine
associa ions be ween mic obial exposu e and epea ed mea-
su es o pa en - epo ed wheezing and cough a di e en
ages. Su i al analyses (disc e e- ime haza d models) we e
used in analyzing as hma e e , cu en as hma, and a opic
de ma i is e e . Logis ic eg ession was used o analyze sensi-
iza ion o inhalan alle gens. The esul s a e p esen ed as
adjus ed odds a ios (aORs) and hei 95% con idence in e -
als (95% CI).
In he analysis o single mic obial ma ke s, he amoun s o
dus and mic obial ma ke s we e gene ally di ided in o h ee
ca ego ies using e iles as cu o s. Fo Wallemia sebi, he
lowes ca ego y consis ed o le els below he limi o de ec-
ion (37.4%) and he es o he alues we e e enly di ided
in o wo g oups (medium and high). S achybo ys cha a um
and AspNeo g oup we e dicho omized a he de ec ion le el
due o high numbe s o nonde ec ed alues. Mic obial di e -
si y sco e was de ined as he sum o all he de ec ed qPCR
ma ke s ( ange 0–8). Due o a low numbe o obse a ions
wi h low and high di e si y, he a iable was ca ego ized in o
ou classes: 0–4, 5, 6, and 7–8.
To al mic obial quan i y sco e was calcula ed as he sum
o h ee ma ke s o he h ee di e en mic obial g oups, ha
is, o ungi, G am-nega i e bac e ia, and G am-posi i e bac-
e ia (one ma ke pe g oup). Single ma ke s we e i s
di ided in o i e g oups using quin iles as cu o s wi h sco es
0, 1, 2, 3, and 4 om lowes o highes and hen summed.
Table 1 Incidence o doc o -diagnosed as hma and a opic de ma i is and he poin p e alence o espi a o y symp oms du ing he i s
6 yea s and p e alence o sensi iza ion o inhalan alle gens a he age o 1 and 6 yea s
A 1 yea A 1.5 yea s A 2 yea s A 3 yea s A 4 yea s A 5 yea s A 6 yea s
Nn%Nn%Nn%Nn%Nn%Nn%Nn %
As hma e e * 389 6 1.5 353 9 2.6 332 14 4.2 291 15 5.2 271 9 3.3 257 6 2.3 247 3 1.2
Cu en
as hma†
353 3 0.9 331 7 2.1 315 8 2.5 290 7 2.4 281 3 1.1 274 4 1.5 270 3 1.1
Wheezing
Apa om
cold
391 41 10.5 358 24 6.7 358 25 7.0 338 23 6.8 358 29 8.1 346 22 6.4 357 25 7.0
Any 391 91 23.3 358 58 16.2 358 67 18.7 339 65 19.2 358 68 19.0 348 46 13.2 357 51 14.3
Cough
Apa om
cold
391 98 25.1 358 66 18.4 358 85 23.7 338 80 23.7 357 91 25.5 348 87 25.0 357 94 26.3
Noc u nal 386 18 4.7 358 47 13.1 358 76 21.2 338 63 18.6 357 78 21.9 348 59 17.0 357 79 22.1
A opic
de ma i is e e ‡
390 61 15.6 300 24 8.0 265 12 4.5 230 14 6.1 211 9 4.3 199 7 3.5 188 2 1.1
Sensi iza ion
o inhalan
alle gens§
374 78 20.9 304 115 37.8
N=in espi o y symp oms: o al numbe o child en wi h in o ma ion on gi en symp om a each ollow-up; in sensi iza ion: o al numbe o
child en wi h IgE esul s a a gi en ime poin ; in as hma e e : o al numbe o child en a each ollow-up who has in o ma ion on as hma
e e a each ollow-up and has no censo ed om he ollow-up due o onse o as hma e e ; in cu en as hma: o al numbe o child en a
each ollow-up who has in o ma ion on as hma e e and as hma medica ion/any wheezing a each ollow-up and has no censo ed om he
ollow-up due o onse o cu en as hma; in a opic de ma i is e e : o al numbe o child en a each ollow-up who has in o ma ion on a opic
de ma i is a each ollow-up and has no censo ed om he ollow-up due o onse o a opic de ma i is. n= he numbe o child en wi h he
p esence o wheezing/cough symp om o wi h posi i e IgE esul , o he numbe o newly diagnosed as hma/cu en as hma/a opic de ma i-
is cases a each ollow-up.
*Doc o -diagnosed as hma e e is de ined as doc o -diagnosed as hma a leas once and/o doc o -diagnosed as hma ic b onchi is mo e han
once du ing he 6-yea ollow-up.
†Cu en as hma is de ined as as hma e e wi h as hma medica ion and/o wheezing symp om pas 12 mon hs a he age o 6 yea s.
‡A opic de ma i is e e is de ined as doco o -diagnosed as opic de ma i is du ing he ollow-up.
§A opic sensi iza ion is de ined as any inhalan sIgE ≥0.35 kU/l a he age o 1 yea and ≥0.70 kU/l a he age o 6 yea s.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d.1094
En i onmen al mic obial exposu e and as hma Ka onen e al.
All possible combina ions wi h measu ed mic obial ma ke s
we e used o c ea e ou di e en o al quan i y sco es o
mic obial exposu e: (1) e gos e ol, endo oxin, and mu amic
acid; (2) b-D-glucan, endo oxin, and mu amic acid; (3) e gos-
e ol, LPS
10:0-16:0
, and mu amic acid; and (4) b-D-glucan,
LPS
10:0-16:0
, and mu amic acid. The c ea ed a iables, wi h
anges om 0 o 12, we e di ided in o i e g oups using
quin iles as cu o s o s a is ical analyses. Linea and qua-
d a ic ends in he associa ions be ween mic obial di e si y
o o al quan i y sco es and heal h ou comes we e es ed
using polynomial con as s (19).
All models we e adjus ed o s udy coho , a ming, and
well-known isk ac o s o as hma (ma e nal his o y o alle -
gic diseases, gende , numbe o olde siblings, smoking du -
ing p egnancy). The models o o al mic obial quan i y sco e
(e gos e ol, endo oxin, and mu amic acid) and as hma e e ,
a opic de ma i is e e , and sensi iza ion o inhalan alle gen
we e ca e ully es ed o 20 addi ional con ounding ac o s,
which ha e been desc ibed ea lie (12). I a con ounde chan-
ged he es ima es o he o al mic obial quan i y sco e by
mo e han 10%, all he models o he ou come we e adjus ed
o he ac o . All he models o espi a o y symp oms and
cu en as hma we e adjus ed o he same con ounding ac-
o s as in he as hma e e models. Gi en an exposu e p e a-
lence o 25%, powe calcula ions (b=80%, a=0.05) show
ha wi h hese da a, we can de ec an odds a io o 2.52 o
as hma e e wi h a popula ion p e alence o 14%. The da a
we e analyzed using SAS 9.2 o Windows (SAS lnc., Ca y,
NC, USA).
Resul s
The p esen analyses included all hose 410 child en wi h
da a on a leas one mic obial ma ke a ailable in any o he
quan i y sco es. O hose, 341 (83%) had he esul s o all
mic obial de e mina ions. Du ing he 6-yea ollow-up, 62 o
389 child en wi h da a on as hma de eloped as hma, and
o hose child en, 35 s ill had cu en as hma a he age o
6 yea s (Table 1). Dis ibu ions o all mic obial ma ke s a e
shown in Table 2.
Mos co ela ions be ween he amoun o house dus and
single mic obial ma ke s as well as in e co ela ions be ween
wo mic obial ma ke s oge he we e be ween 0.30 and 0.85
(Table S1). To al mic obial quan i y sco es we e co ela ed
Table 2 Le els o mic obial ma ke s
N<LOD* (%)
Pe cen iles
25 h Median 75 h 95 h
Amoun o dus (mg/m
2
)†410 0 173 311 587 1332
G am-posi i e bac e ia o ma ke o G am-posi i e bac e ia
Mycobac e ium (cells/m
2
) 399 21 (5.3) 186 857 641 427 1 753 136 7 041 045
S ep omyces (cells/m
2
) 399 7 (1.8) 3923 13 089 45 939 462 289
Mu amic acid (ng/m
2
) 386 7 (1.8) 3122 6616 13 713 34 852
Ma ke o G am-nega i e bac e ia
LPS
10:0–16:0
(nmol/m
2
) 398 2 (0.5) 3 8 15 46
Endo oxin (EU/m
2
) 372 0 2668 6253 13 485 66 569
Fungi o ma ke o ungi
PenAsp g oup (cells/m
2
) 399 3 (0.8) 13 580 59 405 233 616 1 282 236
T ichode ma i ide g oup (cells/m
2
) 400 62 (15.5) 340 2028 9906 153 816
Wallemia sebi (cells/m
2
) 400 152 (38.0) 0 883 11 541 152 041
Cladospo ium (cells/m
2
) 399 50 (12.5) 3652 25 683 104 690 982 138
AspNeo g oup (cells/m
2
) 400 320 (80.0) 0 0 0 14 254
S achybo ys cha a um (cells/m
2
) 400 390 (97.5) 0 0 0 0
EPS (EPSU/m
2
) 374 15 (2.1) 7079 15 312 38 025 126 107
b-D-glucan (lg/m
2
) 376 0 511 970 1818 4066
E gos e ol (ng/m
2
) 401 0 1473 3015 7040 21 978
Quan i y sco es
E gos e ol, endo oxin,
and mu amic acid
347 3 6 9 12
b-D-glucan, endo oxin,
and mu amic acid
352 3 6 9 12
E gos e ol, LPS
10:0–16:0
,
and mu amic acid
380 3 6 9 12
b-D-glucan, LPS
10:0–16:0
,
and mu amic acid
354 3 7 9 12
Di e si y sco e‡399 5 6 6 7
*LOD = he le el o de ec ion, pe cen age o samples unde de ec ion le el om analyzed samples (%).
†The amoun o dus e e s o dus samples used o analyses o qPCRs, e gos e ol, mu amic acid, and LPS (sie ed).
‡The numbe o de ec ed 6 ungal o 2 bac e ial qPCRs.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d. 1095
Ka onen e al. En i onmen al mic obial exposu e and as hma
wi h each o he (a ound =0.90) and also wi h amoun o
dus (a ound =0.85), bu co ela ions be ween o al mic o-
bial quan i y sco es and qPCR esul s we e lowe (a ound
=0.30), excep o Mycobac e ium and he PenAsp g oup
(a ound =0.50). Di e si y sco e had low co ela ions wi h
amoun o dus , all mic obial ma ke s, and o al mic obial
quan i y sco es (a ound =0.20), bu highe wi h Wallemia
sebi ( =0.66).
A
B
Figu e 1 Adjus ed associa ions be ween amoun o dus and bac-
e ial (A) and ungal (B) exposu e a he age o 2 mon hs and
as hma and espi a o y symp oms du ing he i s 6 yea s o li e
and sensi iza ion o inhalan alle gen a he age o 6 yea s. Models
a e adjus ed o s udy coho , a ming s a us, gende , ma e nal his-
o y o alle gic diseases (hay e e , a opic de ma i is, and/o
as hma), smoking du ing p egnancy, he numbe o olde siblings,
and li ing a ea o he home. Models o sensi iza ion o inhalan
alle gens (cu poin ≥0.70 kU/l) a e addi ionally adjus ed o loo
ype o dus sampling.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d.1096
En i onmen al mic obial exposu e and as hma Ka onen e al.

In gene al, he associa ions o single mic obial ma ke s wi h
as hma e e and espi a o y symp oms we e mos ly nonsigni -
ican , while he shape o he associa ion a ied (Fig. 1). To al
mic obial quan i y sco e had a signi ican in e ed-U-shaped
associa ion wi h as hma e e : he highes isk o as hma e e
was ound wi h he medium le el o o al mic obial quan i y
sco e and he lowes isk wi h he highes quan i y sco e
(Fig. 2, Table 3). The associa ion was independen o he
di e si y sco e. The associa ions we e qui e simila o cu en
as hma (Table 3) and when using o he mic obial ma ke s
han e gos e ol, endo oxin, and mu amic acid o c ea e he
o al mic obial quan i y sco e (Table S2) as well as when
using EPS as a ma ke o ungi (da a no shown). To al
mic obial quan i y sco es ended o be in e sely associa ed
wi h espi a o y symp oms (Table S2). The in e ed-U-shaped
associa ion be ween o al mic obial quan i y sco e and
as hma e e ended o be s onge a e adjus ing o he
amoun o dus (da a no shown). Adjus men o dus also
s eng hened he associa ions be ween as hma, and S ep o-
myces, endo oxin, PenAsp g oup, b-D-glucan and e gos e ol,
bu no he o he single mic obial ma ke s (da a no shown).
The associa ions be ween o al mic obial quan i y sco e and
any wheezing we e simila among child en who we e sensi ized
agains a leas one o he es ed inhalan o ood alle gens a
he age o 6 yea s and who we e no sensi ized (P- alue =0.66
o in e ac ion e m). In con as , in he s a i ied analyses, he
in e ed-U-shaped associa ions be ween he quan i y sco es
and as hma e e we e always s onge among nona opic han
among a opic child en, bu he P- alues o in e ac ion anged
be ween 0.08 and 0.28 (da a no shown). The e we e no in e -
ac ions wi h bi h coho s (P- alues ≥0.27 o in e ac ion
e ms). Associa ions be ween o al mic obial quan i y sco e
and any wheezing we e also simila in a ms and in u al/sub-
u ban a eas (P- alue =0.58 o in e ac ion e m). Due o he
low numbe s o child en wi h as hma e e among a me s,
in e ac ion es s be ween o al mic obial quan i y sco e and
a ming on as hma e e could no be pe o med.
Di e si y sco e was associa ed wi h a dec eased isk o any
wheezing, and a simila endency was seen wi h as hma e e
and cu en as hma (Table 3). The associa ion wi h as hma
e e was, howe e , ai ly sensi i e o di e en adjus men s,
especially adjus men o a ming. The associa ion wi h any
wheezing was simila among child en om a ms and om
u al/subu ban a eas as well as child en who we e sensi ized
agains a leas one o he es ed inhalan o ood alle gens a
he age o 6 yea s and who we e no sensi ized (P- alues
≥0.4 o in e ac ion e ms) (da a no shown).
Mos o he associa ions be ween single mic obial ma ke s
and a opic de ma i is and sensi iza ion o inhalan alle gens
a he age o 1 (Table S3) and 6 yea s (Fig. 1) we e nonsig-
ni ican . To al mic obial quan i y sco e was no associa ed
wi h a opic de ma i is o sensi iza ion o inhalan alle gen a
he age o ei he 1 yea (da a no shown) o 6 yea s
(Table 3). Di e si y sco e was signi ican ly (in e ed-U shape)
associa ed wi h sensi iza ion o inhalan alle gen a he age o
6 yea s (Table 3), while simila endency, hough nonsigni i-
can , was seen wi h sensi iza ion o inhalan alle gen a
1 yea (Table S4). No associa ion was ound be ween di e -
si y sco e and a opic de ma i is (Table S4).
Discussion
The p esen s udy sugges s ha an index o o al quan i y o
en i onmen al mic obial exposu e may p edic as hma be e
han single mic obial ma ke s, independen ly o mic obial
di e si y sco e and amoun o dus . The di e si y sco e
dec eased he isk o wheezing and was signi ican ly
(in e ed-U shape) associa ed wi h sensi iza ion o inhalan
alle gens. Only a ew associa ions we e obse ed be ween sin-
gle mic obial ma ke s and he ou comes s udied.
This is he i s s udy using an index o o al mic obial
quan i y sco e when s udying he isk o as hma. P e iously,
one c oss-sec ional s udy ound a endency o in e se associa-
ion be ween mic obial quan i y sco e (LPS
10:0–16:0
, e gos-
e ol, and mu amic acid) and alle gic sensi iza ion (9).
Typically, epidemiological s udies ha e used only one mic o-
bial ma ke as a su oga e o o al mic obial exposu e.
Howe e , i is clea ha such assessmen s p o ide an incom-
ple e pic u e o he o al quan i y and quali y o human
mic obial exposu e. Due o high co ela ions, a majo di i-
cul y o ea lie s udies has been o sepa a e he e ec s o sin-
gle mic obial ma ke s om each o he and om he e ec o
he amoun o dus (5, 20). In he p esen s udy, o al mic o-
bial quan i y sco e p edic ed he isk o as hma indepen-
den ly o mic obial di e si y and amoun o dus .
The eason behind he obse ed associa ion be ween o al
mic obial quan i y sco e and as hma is unclea . A po en ial
explana ion is ha di e en componen s o mic obial g oups
o gene a sha e common an igen o molecule s uc u es on
hei cell wall su ace, which a e de ec ed by pa e n ecogni-
ion ecep o s in inna e immuni y cells and ha e a p o ound
in luences on he immune sys em (21). I o al exposu e o
Figu e 2 Risk o as hma in ela ion o o al mic obial quan i y sco e
in quin iles (sum o e gos e ol, endo oxin, and mu amic acid) (aOR).
Model is adjus ed o s udy coho , a ming s a us, gende , ma e -
nal his o y o alle gic diseases (hay e e , a opic de ma i is, and/o
as hma), smoking du ing p egnancy, he numbe o olde siblings,
li ing a ea o he home, and di e si y sco e.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d. 1097
Ka onen e al. En i onmen al mic obial exposu e and as hma
Table 3 Adjus ed associa ions be ween mic obial quan i y o di e si y sco es and as hma o espi a o y symp oms up o he age o 6 yea s and cu en as hma and sensi iza ion o inhalan
alle gen a 6 yea s o age
As hma e e Cu en as hma Any wheezing¥Noc u nal cough¥
Sensi iza ion o inhalan
alle gens a 6 yea s¤
N#nN‡aOR (95% CI) N#nN‡aOR (95% CI) aOR (95% CI) aOR (95% CI) NnaOR (95% CI)
Quan i y sco e£
Re e ence
(1s quin ile)
63 8 354 1 56 5 352 1 1 1 53 19 1
2nd quin ile 73 12 390 1.73 (0.67–4.45) 63 6 380 1.32 (0.38–4.61) 0.65 (0.35–1.22) 0.68 (0.39–1.21) 57 26 2.19 (0.92–5.23)
3 d quin ile 62 13 300 2.24 (0.87–5.75)^ 57 7 297 2.01 (0.59–6.79) 0.89 (0.49–1.62) 0.86 (0.48–1.55) 44 17 1.42 (0.55–3.64)
4 h quin ile 56 11 311 1.78 (0.67–4.69) 53 7 318 1.86 (0.55–6.32) 0.98 (0.55–1.75) 0.70 (0.40–1.24) 47 17 1.32 (0.51–3.40)
5 h quin ile 75 3 438 0.34 (0.09–1.36) 67 2 409 0.39 (0.07–2.11) 0.73 (0.43–1.24) 0.68 (0.38–1.20) 57 20 1.50 (0.61–3.70)
P- alue <0.001¶0.03¶0.95¶0.74¶0.46¶
Di e si y sco e§
Re e ence (0–4) 45 9 232 1 37 8 215 1 1 1 33 11 1
5 108 13 566 0.69 (0.27–1.78) 95 7 557 0.30 (0.10–0.89)* 0.68 (0.38–1.20) 0.90 (0.50–1.62) 81 36 2.10 (0.84–5.27)
6 133 22 736 1.03 (0.43–2.49) 122 10 731 0.35 (0.12–0.94)* 0.54 (0.30–0.97)* 1.23 (0.71–2.15) 108 46 2.16 (0.86–5.45)
7–8 43 3 259 0.64 (0.15–2.76) 42 2 253 0.40 (0.07–2.29) 0.14 (0.06–0.32)** 1.21 (0.58–2.50) 36 6 0.42 (0.12–1.50)
P- alue 0.67†0.31†<0.001†0.45†0.001¶
£Sum o quin iles o loads o e gos e ol, endo oxin, and mu amic acid.
§Numbe o de ec ed qPCRs.
Models a e adjus ed o ime, s udy coho , a ming s a us, gende , ma e nal his o y o alle gic diseases (hay e e , a opic de ma i is, and/o as hma), smoking du ing p egnancy, he num-
be o olde siblings, li ing a ea o he home, and ei he di e si y sco e o quan i y sco e.
N# To al numbe o child en in he beginning o ollow-up, n=numbe o cases in each ca ego y.
N‡Subjec s con ibu ed up o se en epea ed obse a ions o his su i al analysis using disc e e- ime haza d models (DTH).
¥Subjec s con ibu ed up o se en epea ed obse a ions o his analysis using gene alized es ima ing equa ions.
¤Models a e addi ionally adjus ed o loo ype o dus sampling.
P- alue ^<0.1, *<0.05, **<0.01, †P- alue o linea end es , ¶P- alue o quad a ic end es .
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d.1098
En i onmen al mic obial exposu e and as hma Ka onen e al.
such s uc u es is he main causal ac o explaining he asso-
cia ion be ween mic obial exposu e and lowe isk o alle gic
diseases, hen o al mic obial quan i y sco e is likely o be e
e lec his exposu e han single mic obial ma ke s. Va ying
co ela ions o single mic obial ma ke s wi h o al mic obial
exposu e would hen explain he o en weak and con lic ing
indings om ea lie s udies. In addi ion, some s udies ha e
shown syne gis ic in e ac ions be ween di e en exposing
agen s (22), and an index o o al mic obial quan i y sco e
may cap u e such syne gis ic e ec s. Da a om deep
sequencing o mic obial exposu e (23) will gi e oppo uni ies
o explo e u he he abo e po en ial mechanisms.
To al mic obial quan i y sco e had an in e ed-U-shaped
associa ion wi h as hma. P e ious s udies ha e sugges ed ha
he immune sys em may eac i s wi h enhanced esponse
and subsequen ly wi h ole ance (24). Associa ions o simila
shape ha e also been epo ed ea lie be ween alle gen le els
and b-D-glucan, and isk o as hma, wheezing, o a opic sen-
si iza ion (25–27). The shape o he associa ion in he p esen
s udy may also ela e o some unknown cha ac e is ics o he
p esen s udy, gi en ha some single mic obial ma ke s also
showed an associa ion o a simila shape. Fu he s udies in
la ge coho s and in di e en se ings a e needed o be e
de ine he shape o he associa ion be ween o al mic obial
quan i y sco e and isk o as hma.
We ound a simila in e se associa ion be ween measu ed
mic obial di e si y sco e and wheezing, as has been epo ed
wi h as hma in wo ecen c oss-sec ional s udies (8). The asso-
cia ion wi h as hma was nonsigni ican , hough in he same
di ec ion. The e we e di e ences in he mic obiological me h-
ods used be ween he p esen s udy and p e ious s udies. We
used qPCR, a me hod ha quan i a i ely desc ibes he p es-
ence o speci ic iable and non iable o ganisms o p io chosen
mic obes (28). The p e ious s udies ei he cul i a ed iable
mic obes (GABRIELA s udy) o used single-s and con o ma-
ion polymo phism analyses, which is a quali a i e a he han
quan i a i e me hod (PARSIFAL s udy) (8). We calcula ed a
di e si y sco e based on 6 ungal and 2 bac e ial qPCR assays
ep esen ing ei he mic obial species, gene a, o g oups, which
hence only p o ides a sugges i e and ough es ima e o he
o e all mic obial di e si y. None heless, he esul s a e in line
wi h p e ious s udies (8) a ge ing a b oade spec um o
mic obes. Taken oge he , he s udies sugges ha mic obial
di e si y sco e may p edic as hma and may be a use ul ma ke
o desc ibe he quali y o mic obial exposu e.
The obse ed associa ions be ween s udied heal h ou -
comes and single mic obial ma ke s should be in e p e ed
wi h cau ion, as no adjus men s o mul iple es ing we e
done. The mos in e es ing indings we e maybe he p o ec-
i e associa ions in he case o G am-posi i e bac e ia (Myco-
bac e ium spp., S ep omyces spp., and mu amic acid), which
ha e been epo ed ea lie o mu amic acid (6, 29).
The main s eng hs o he p esen s udy a e he p ospec i e
bi h coho design wi h high pa icipa ion a e ( a ied
be ween 80% and 95% in each ollow-up) and a good a ie y
o measu ed ma ke s o exposu e o en i onmen al mic obes.
The small size o ou s udy coho is he main limi a ion o
he s udy, and he esul s need o be con i med in u he s ud-
ies. The mic obial ma ke s and combina ions o hose used o
build o al mic obial quan i y sco es in he p esen s udy
do no measu e o al mic obial exposu e wi hou e o , o
example using mu amic acid oge he wi h endo oxin o e es i-
ma es he amoun o G am-nega i e bac e ia, because mu amic
acid is ound also in G am-nega i e bac e ia, al hough o a
lesse ex en (30). These weaknesses do no , howe e , appea o
be a majo p oblem, as he di e en quan i y sco es used in he
p esen s udy showed e y simila associa ions.
In conclusion, ou indica o o o al quan i y o mic obial
exposu e p edic ed as hma be e han single mic obial ma k-
e s. De ec ed associa ions we e independen o he measu ed
mic obial di e si y and amoun o dus . Be e indica o s o
o al quan i y and di e si y o mic obial exposu e a e needed
in s udies on he de elopmen o as hma.
Acknowledgmen s
We would like o hank he amilies o hei pa icipa ion in
he s udy and s udy nu ses Raija Jun unen, Riikka Juola,
and Seija An ikainen o ield wo k; Hanna Lepp€
anen, Ka ja
Saa nio, Heli Ma ikainen, Susanne an den B ink, Timmo y
Wigboldus, Mi ian Boe e, Sieg ied de Wind, and Jack
Spi ho en o mic obiological analyses; Pekka Tii anen
o suppo in s a is ical analyses and da a managemen ;
Hanna-Ma i Takkinen o illus a ions, Asko Veps€
al€
ainen
and Timo Kauppila o da a managemen ; and Ma k Phillips
o e ising he language o his manusc ip .
Funding
This s udy was suppo ed by esea ch g an s om he
Eu opean Union QLK4-CT-2001-00250; G adua e School in
En i onmen al Heal h (SYTYKE); EVO- unding; Fa me s’
Social Insu ance Ins i u ion (Mela); he Academy o Finland
(g an 139021); he Juho Vainio Founda ion; he Eu opean
commission as pa o HITEA (Heal h E ec s o Indoo Pollu-
an s: In eg a ing mic obial, oxicological and epidemiological
app oaches), G an ag eemen no. 211488 unde he Se en h
F amewo k P og amme, Topic ENV.2007.1.2.1.1. ‘Indoo ai
pollu ion in Eu ope: An eme ging en i onmen al heal h issue’;
and by he Na ional Ins i u e o Heal h and Wel a e, Finland.
Au ho con ibu ions
All au ho s app o ed he submi ed e sion. Ka onen
in ol ed in s a is ical da a analyses, da a collec ing, manu-
sc ip p epa a ion, and d a ing. Hy €
a inen and Rin ala
in ol ed in dus sampling assessmen , mic obial analyses,
and manusc ip p epa a ion. Ko ppi and Remes in ol ed in
au ho i y on pedia ic issues and manusc ip p epa a ion.
T
aubel, Keski-Nisula, and Lampi in ol ed in manusc ip
p epa a ion. Doekes and Geh ing in ol ed in mic obial
analyses and manusc ip p epa a ion. Renz and P e e le
in ol ed in IgE measu emen s and manusc ip p epa a ion.
Genunei in ol ed in da a managemen and manusc ip p ep-
a a ion. on Mu ius and Pekkanen in ol ed in s udy concep
and design, and manusc ip p epa a ion.
Alle gy 69 (2014) 1092–1101 ©2014 The Au ho s. Alle gy Published by John Wiley & Sons L d. 1099
Ka onen e al. En i onmen al mic obial exposu e and as hma
Con lic s o in e es
The au ho s decla e ha hey ha e no con lic s o in e es .
Suppo ing In o ma ion
Addi ional Suppo ing In o ma ion may be ound in he
online e sion o his a icle:
Table S1. Spea man co ela ions o mic obial ma ke s pe
sampled a ea (/m
2
).
Table S2. Adjus ed associa ions be ween quan i y o di e -
si y sco es and as hma o espi a o y symp oms.
Table S3. Adjus ed associa ions be ween mic obial expo-
su e and a opic de ma i is up o he age o 6 yea s and sensi-
iza ion o inhalan alle gen a he age o 1 yea .
Table S4. Associa ions be ween mic obial di e si y and
a opic de ma i is e e un il he age o 6 yea s and sensi iza-
ion o inhalan alle gen a he age o 1 and 6 yea s.
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