Skip to main content

Table 2 Associationsa between maternal smoking during pregnancy and offspring type 1 diabetes in different study designs

From: Maternal smoking during pregnancy and type 1 diabetes in the offspring: a nationwide register-based study with family-based designs

Smoking status Non-smoking 1–9 cigarettes/day  ≥ 10 cigarettes/day P
Cohort analysis
 No. of cases 16,084 1684 849  
 Person years 38,819,013 5,235,610 2,863,183  
 Incidence (no./10,000 person years) 4.1 3.2 3.0  
 Model 1 1.00 0.80 (0.76–0.85) 0.75 (0.70–0.80) 0.100
 Model 2 1.00 0.80 (0.76–0.84) 0.74 (0.69–0.80) 0.076
 Model 3 1.00 0.80 (0.76–0.85) 0.74 (0.69–0.80) 0.066
Cousin comparison analysis
 No. of cases 6765 801 422  
 Model 1 1.00 0.75 (0.68–0.83) 0.69 (0.60–0.79) 0.245
 Model 2 1.00 0.75 (0.68–0.83) 0.67 (0.58–0.77) 0.114
 Model 3 1.00 0.75 (0.68–0.83) 0.66 (0.58–0.76) 0.111
Sibling comparison analysis
 No. of cases 12,483 1193 608  
 Model 1 1.00 0.79 (0.71–0.89) 0.70 (0.60–0.83) 0.116
 Model 2 1.00 0.80 (0.71–0.90) 0.71 (0.60–0.84) 0.119
 Model 3 1.00 0.80 (0.71–0.90) 0.71 (0.60–0.84) 0.115
  1. Model 1 was adjusted for sex and year of birth. The Cox model in the cohort analysis was fitted with a gamma-frailty component to account for the clustering of siblings from the same mother. The conditional logistic model in the sibling (or cousin) comparison analysis conditioned on sibling (or cousin) groups
  2. Model 2 was additionally adjusted for maternal education, paternal education, maternal age at delivery, maternal body mass index during pregnancy, maternal history of diabetes, paternal history of diabetes, and birth order based on model 1
  3. Model 3 was additionally adjusted for gestational age and birth weight for gestational age based on model 2
  4. The P value indicted whether there was a difference in the incidence of type 1 diabetes between maternal smoking 1–9 cigarettes/day and ≥ 10 cigarettes/day
  5. aHazard ratios (95% confidence intervals) are presented for the cohort analysis, and odds ratios (95% confidence intervals) are presented for the cousin and sibling comparison analyses