Birth weight and risk of type 2 diabetes: a systematic review.
BACKGROUND
Low birth weight is implicated as a risk factor for type 2 diabetes. However, the strength, consistency, independence, and shape of the association have not been systematically examined.


OBJECTIVE
To conduct a quantitative systematic review examining published evidence on the association of birth weight and type 2 diabetes in adults.


METHODS
Relevant studies published by June 2008 were identified through literature searches using EMBASE (from 1980), MEDLINE (from 1950), and Web of Science (from 1980), with a combination of text words and Medical Subject Headings. Studies with either quantitative or qualitative estimates of the association between birth weight and type 2 diabetes were included.


METHODS
Estimates of association (odds ratio [OR] per kilogram of increase in birth weight) were obtained from authors or from published reports in models that allowed the effects of adjustment (for body mass index and socioeconomic status) and the effects of exclusion (for macrosomia and maternal diabetes) to be examined. Estimates were pooled using random-effects models, allowing for the possibility that true associations differed between populations.


RESULTS
Of 327 reports identified, 31 were found to be relevant. Data were obtained from 30 of these reports (31 populations; 6090 diabetes cases; 152 084 individuals). Inverse birth weight-type 2 diabetes associations were observed in 23 populations (9 of which were statistically significant) and positive associations were found in 8 (2 of which were statistically significant). Appreciable heterogeneity between populations (I(2) = 66%; 95% confidence interval [CI], 51%-77%) was largely explained by positive associations in 2 native North American populations with high prevalences of maternal diabetes and in 1 other population of young adults. In the remaining 28 populations, the pooled OR of type 2 diabetes, adjusted for age and sex, was 0.75 (95% CI, 0.70-0.81) per kilogram. The shape of the birth weight-type 2 diabetes association was strongly graded, particularly at birth weights of 3 kg or less. Adjustment for current body mass index slightly strengthened the association (OR, 0.76 [95% CI, 0.70-0.82] before adjustment and 0.70 [95% CI, 0.65-0.76] after adjustment). Adjustment for socioeconomic status did not materially affect the association (OR, 0.77 [95% CI, 0.70-0.84] before adjustment and 0.78 [95% CI, 0.72-0.84] after adjustment). There was no strong evidence of publication or small study bias.


CONCLUSIONS
In most populations studied, birth weight was inversely related to type 2 diabetes risk.
Whincup
Peter H
PH
Division of Community Health Sciences, St George's, University of London, Cranmer Terrace, London SW17 0RE, England. p.whincup@sgul.ac.uk
Kaye
Samantha J
SJ
Owen
Christopher G
CG
Huxley
Rachel
R
Cook
Derek G
DG
Anazawa
Sonoko
S
Barrett-Connor
Elizabeth
E
Bhargava
Santosh K
SK
Birgisdottir
Bryndís E
BE
Carlsson
Sofia
S
de Rooij
Susanne R
SR
Dyck
Roland F
RF
Eriksson
Johan G
JG
Falkner
Bonita
B
Fall
Caroline
C
Forsén
Tom
T
Grill
Valdemar
V
Gudnason
Vilmundur
V
Hulman
Sonia
S
Hyppönen
Elina
E
Jeffreys
Mona
M
Lawlor
Debbie A
DA
Leon
David A
DA
Minami
Junichi
J
Mishra
Gita
G
Osmond
Clive
C
Power
Chris
C
Rich-Edwards
Janet W
JW
Roseboom
Tessa J
TJ
Sachdev
Harshpal Singh
HS
Syddall
Holly
H
Thorsdottir
Inga
I
Vanhala
Mauno
M
Wadsworth
Michael
M
Yarbrough
Donald E
DE
D000328:Adult; D000368:Aged; D001724:Birth Weight; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D006801:Humans; D008875:Middle Aged; D012306:Risk