Maternal age at delivery and order of birth are risk factors for type 1 diabetes mellitus in Upper Silesia, Poland.
BACKGROUND
Parental age and birth order as risk factors for childhood type 1 diabetes mellitus were investigated using data from the Regional Diabetic Center for Upper Silesia, Poland, in a population-based study of 398 children with type 1 DM aged 0-14 years born between 1979-1996.


METHODS
Noting differences in the proportions of children of different birth order between cases and controls, the data were stratified by birth order. For each stratum, odds ratios and their 95% confidence intervals were calculated to assess risks related to the mother's age. The homogeneity of the odds ratios related to the mother's age between strata was evaluated by the Mantel-Haenszel method. Risks related to mother's age and birth order were also estimated jointly by multivariable logistic regression.


RESULTS
Decreased risk in later children compared with firstborns was noted. Increased maternal age was found to be a risk factor for type 1 DM. An increase in the mother's age by one year increases the risk of the child being affected by type 1 DM 1.07 times, and children born as the nth in the family are 1.59 times less exposed to the same risk than those born as the (n-1)th.


CONCLUSIONS
Children of different birth order have different risks of being affected by type 1 DM. Increased maternal age at the time of delivery is a risk factor for type 1 DM in Upper Silesia, Poland. To avoid bias in estimating risks, the mother's age and child's sequence number should be analyzed jointly.
Polańska
Joanna
J
Faculty of Automatic Control, Electronics, and Computer Science, Silesian University of Technology, Gliwice, Poland. jkp@stat.rice.edu
Jarosz-Chobot
Przemysława
P
D000293:Adolescent; D000328:Adult; D001722:Birth Order; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D016017:Odds Ratio; D011044:Poland; D011247:Pregnancy; D012307:Risk Factors