Early introduction of dairy products associated with increased risk of IDDM in Finnish children. The Childhood in Diabetes in Finland Study Group

Associations between infant-feeding patterns and risk of IDDM were investigated in a nationwide Finnish case-control study of 690 IDDM children < 15 yr of age. Each child was matched by date of birth and sex to a randomly selected population-based control child. Univariate analysis revealed that the risk of IDDM was increased by approximately 1.5 in children for whom breast-feeding was terminated at < 2 mo of age, doubled in those who were exclusively breast-fed for < 2 mo, and doubled in those who were introduced to dairy products at < 2 mo of age. In further multivariate analyses of these factors, it was found that introduction of dairy products at an early age was the most important risk factor, and the observed univariate effects of duration of breast-feeding variables were explained by their correlation with this factor. This is the first observational study to show that early introduction of dairy products is independently associated with an increased risk of IDDM. Adjustment for mother's education and age, child's birth order, or birth weight did not affect the results.

The epidemic cycle of Chlamydia pneumoniae infection in eastern Finland, 1972-1987

The epidemic cycle of Chlamydia pneumoniae infection was examined in two areas in eastern Finland over a period of 15 years, 1972-87. The C. pneumoniae IgG antibody prevalence was determined with 5-year intervals in a random sample of the population aged 25-59 years. The total number of sera studied using immunofluorescence was 2387. In 1972 the antibody prevalence was 57% and it increased to 66% in 1977. Over the next 5 years the prevalence decreased to 44% in 1982, but by 1987 it had again increased to 59%. The temporal variation in prevalence was statistically significant (P < 0.001) and similar for both genders. Throughout the observation period the overall prevalence was 7-11% higher in men than in women (P < 0.01). The antibody prevalence increased with age, being the highest among the oldest study subjects of both genders. The periods of high and low prevalence alternated in an epidemic cycle (P < 0.001) of about 10 years.

Empirical Bayes methods for testing associations with large numbers of candidate genes in the presence of environmental risk factors, with applications to HLA associations in IDDM

Standard regression models for disease incidence data can be used to test for associations between a disease and measured genetic and environmental factors and their interactions. Complications arise when the gene is not observed, requiring segregation and linkage analysis approaches, or when the candidate gene(s) are found to be highly polymorphic, as in the HLA region. We propose a Bayesian approach to the latter problem, in which the log relative risks for all alleles at a given locus are taken to be independent and exchangeable, assuming there is no preferential zygotic assortment and negligible recombination. Multi-locus problems can be addressed either by adding exchangeable interaction terms or by adopting a multivariate prior for haplotype effects. Some simulations based on our current work on family studies of IDDM are discussed.

Prevalence of diabetes mellitus and impaired glucose tolerance in the middle-aged population of three areas in Finland

The prevalence of diabetes mellitus and impaired glucose tolerance (IGT) was determined in a random sample of the population aged 45-64 years in three areas of Finland. The two-hour oral glucose tolerance test was repeated in subjects whose first test suggested abnormal glucose tolerance. In the final classification, based on the results of the two tests, the age-standardized prevalence of diabetes, according to the WHO criteria was 5.7% (95% confidence interval (CI): 4.3-7.1) in men and 4.6% (95% CI: 3.6-5.0) in women. The prevalence of IGT was 3.1% (95% CI: 2.1-4.1) in men and 5.1% (95% CI: 3.9-6.3) in women. Among those aged 55-64 years the prevalence was 6.9% in men and 7.5% in women. The prevalence of diabetes and IGT were not different between the three areas. The age-specific mean values of fasting and two-hour blood concentrations and the 90th percentiles of the blood glucose distributions were also not different between the areas. The prevalence of IGT and diabetes increased with age more steeply among women than men. The median of fasting blood glucose did not change, but the 90th percentile increased with increasing age. The entire distribution of two-hour blood glucose shifted towards higher values with ageing, but the major increase was seen for the 95th percentile. The majority of the diabetic subjects were aware of their condition. The awareness was better among men than women.