Paternal smoking is associated with a decreased prevalence of type 1 diabetes mellitus among offspring in two national British birth cohort studies (NCDS and BCS70)

Aims: An association between paternal age and type 1 diabetes
(IDDM) among their offspring was recent reported as well as
transgenerational responses in humans. This paper aims to assess
the association of markers for prenatal exposures with IDDM.
Methods: We analysed data from two birth cohorts in Great Britain
on 5214 cohort members from the National Child Development Study
(NCDS) and 6068 members of the 1970 British Birth Cohort Study
(BCS70) with full information on IDDM and explanatory variables
using multivariate logistic regression. Results: IDDM prevalence
was 0.7% (95% CI 0.5-1.0%; n = 38) in the NCDS and 0.4% (95% CI
0.3-0.6%; n = 27) in the BCS70 cohort. Paternal age was not
associated with IDDM possibly due to lack of sample power.
Unexpectedly, a lowered prevalence of IDDM was observed among
offspring of smoking fathers in both cohorts, with a combined odds
ratio of 0.44 (95% CI 0.25-0.75). This association could not be
explained by maternal smoking prior to, during or after pregnancy,
number of siblings, parental social class, maternal and paternal
age, or cohort. Maternal smoking in pregnancy did not alter the
IDDM prevalence among offspring. Conclusions: This unexpected
finding may be explained by germ-line mutations or other mechanisms
associated with paternal smoking. This phenomenon should be
investigated and these results should not be used as a
justification for smoking. Paternal exposures may be important in
determining IDDM risk.