Background: Infant adiposity may be influenced by several environmental risk factors, but few studies have explored these interactions.
Objective: To examine the interaction between exposure to secondhand smoke and breastfeeding exclusivity on adiposity at age 5 months.
Methods: We studied 813 mother-offspring pairs from the longitudinal Healthy Start study. Fat mass and fat-free mass were measured by air displacement plethysmography. Linear regression analyses were used to estimate the association between household smokers (none, any) with fat mass, fat-free mass, percent fat mass, weight-for-age z-score, weight-for-length z-score and BMI-for-age z-score as separate outcomes. Interaction terms between household smokers and breastfeeding exclusivity (<5 months, ≥5 months) were added to separate models.
Results: The combination of exposure to secondhand smoke and a lack of exclusive breastfeeding was associated with increased adiposity at age 5 months. For example, within the not exclusively breastfed strata, exposure to secondhand smoke was associated with increased fat mass (0.1 kg; 95% CI: 0.0-0.2; P = 0.05). Conversely, within the exclusively breastfed strata, there was virtually no difference in fat mass between exposed and non-exposed infants (coefficient: -0.1; 95% CI: -0.3-0.1; P = 0.25).
Conclusions: Our findings may inform new public health strategies with potential relevance for both smoking cessation and obesity prevention.
Keywords: Adiposity; breastfeeding; effect modification; interaction; secondhand smoke.
© 2017 World Obesity Federation.