Seasonality of birth in children and young adults (0-29 years) with type 1 diabetes in Ukraine.
OBJECTIVE
Numerous epidemiological studies have shown differences in seasonality of birth patterns between the general population and the group who develop type 1 diabetes mellitus. This finding indicates that environmental factors operating during pre- and/or postnatal development could be aetiologically important. We examined whether the pattern of month of birth for type 1 diabetes patients in Ukraine differs from that for total live births.


METHODS
Data consist of prevalent cases of type 1 diabetes in Ukraine by the end of 2003. Cases are restricted to persons born after 1 January 1960, diagnosed with type 1 diabetes before the age of 30 years (n = 20,117). People born during the same time in the general population (n = 29,105,560) were the reference standard. Seasonal patterns were estimated using logistic regression with harmonic terms.


RESULTS
We found a strongly significant seasonal pattern of type 1 diabetes incidence rates (p < 0.001), with the lowest rates in December and the highest in April. The rate ratio between the extremes was 1.32 (95% CI 1.27-1.39). Tests for seasonal patterns in subgroups defined by sex and age or by sex and date of birth were all significant with p values less than 0.02. We found no interactions with sex (p = 0.142) or age at diagnosis (p = 0.207), but found a strong interaction with period of birth (p < 0.0001).


CONCLUSIONS
The results obtained indicate that early-life factors linked to seasons may influence type 1 diabetes risk later in life.
Vaiserman
A M
AM
Laboratory of Mathematical Modelling of Ageing Processes, Institute of Gerontology, Vyshgorodskaya st. 67, Kiev 04114, Ukraine. vaiserman@geront.kiev.ua
Carstensen
B
B
Voitenko
V P
VP
Tronko
M D
MD
Kravchenko
V I
VI
Khalangot
M D
MD
Mechova
L V
LV
D000293:Adolescent; D000328:Adult; D001719:Birth Certificates; D001723:Birth Rate / Q000208:ethnology / Q000639:trends*; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000208:ethnology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D012307:Risk Factors; D012621:Seasons; D014455:Ukraine