Table 3.

Associations of in utero tobacco smoke with incident asthma, by parental education and parental stress

Risk factorStratumN (%)*Hazard ratio (95% confidence interval)Interaction P value
Maternal smoking in uteroAll subjects156 (6.3)1.49 (0.79, 2.80)
Low parental education16 (3.2)5.69 (1.88, 17.3)§0.03
High parental education137 (7.3)1.10 (0.51, 2.41)
High parental stress89 (7.5)2.66 (1.33, 5.33)§0.03
Low parental stress62 (5.4)0.30 (0.04, 2.18)
  • *Denominator varies due to missing data about maternal smoking in utero, parental education and parental stress.

  • All models are adjusted for race/ethnicity with baseline strata for age and gender and community random effects.

  • P value based on the χ 2 statistic using the likelihood ratio test to compare a model with base terms only to a model also containing the multiplicative interaction term. Interactions involving parental stress are based on a continuous variable describing the PSS.

  • §Indicates P value < 0.05.