Importance of familial factors in associations between offspring birth weight and parental risk of type-2 diabetes.
BACKGROUND
It is hypothesized that associations found between birth weight and subsequent risk of type-2 diabetes are due to inherited genes affecting both fetal growth and metabolism of insulin.


METHODS
To study whether there is a familial (shared environmental and genetic) link between birth weight and type-2 diabetes, the authors used a sample of 11,411 Swedish like-sexed twins born from 1926 to 1958 with at least one offspring, to study the association between offspring birth weight for gestational age and parental risk of type-2 diabetes.


RESULTS
Decreasing offspring birth weight for gestational age (with 1 SD) was associated with an increased risk of type-2 diabetes among father's [odds ratio (OR)=1.72, 95% confidence interval (CI): 1.33-2.23] and decreased risk among mothers (OR=0.43, 95% CI: 0.30-0.62), independent of grand parental and parental socio-economic status and parental smoking. In paired twin analysis, the association between offspring birth weight and mothers with risk of type-2 diabetes was similar within- and between-twin pairs, whereas father's risk was slightly smaller within than between pairs (OR(Between)=1.90, 95% CI: 1.10-3.28, and OR(Within)=1.71, 95% CI: 1.10-2.67, respectively).


CONCLUSIONS
The well-established association between paternal type-2 diabetes and offspring birth weight seems to primarily be due to as yet unidentified non-shared environmental factors. However, familial factors shared within twin pairs may contribute to the association.
Bergvall
Niklas
N
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. niklas.bergvall@ki.se
Lindam
Anna
A
Pawitan
Yudi
Y
Lichtenstein
Paul
P
Cnattingius
Sven
S
Iliadou
Anastasia
A
D001724:Birth Weight / Q000235:genetics*; D016000:Cluster Analysis; D015331:Cohort Studies; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D005220:Fathers; D005260:Female; D005320:Fetal Macrosomia / Q000235:genetics*; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease / Q000453:epidemiology*; D018392:Genomic Imprinting; D005865:Gestational Age; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007333:Insulin Resistance / Q000235:genetics; D008297:Male; D009035:Mothers; D016017:Odds Ratio; D010375:Pedigree; D011247:Pregnancy; D011336:Probability; D012189:Retrospective Studies; D018570:Risk Assessment; D012959:Socioeconomic Factors; D013548:Sweden / Q000453:epidemiology; D014427:Twins