Joint association between birth weight at term and later life adherence to a healthy lifestyle with risk of hypertension: a prospective cohort study

Yanping Li, Sylvia H. Ley, Tyler J. VanderWeele, Gary C. Curhan, Janet W. Rich-Edwards, Walter C. Willett, John P. Forman, Frank B. Hu, Lu Qi

Low birth weight and unhealthy lifestyles in adulthood have been independently associated with an elevated risk of hypertension. However, no study has examined the joint effects of these factors on incidence of hypertension. We followed 52,114 women from the Nurses' Health Study II without hypercholesterolemia, diabetes, cardiovascular disease, cancer, prehypertension, and hypertension at baseline (1991-2011). Women born preterm, of a multiple pregnancy, or who were missing birth weight data were excluded. Unhealthy adulthood lifestyle was defined by compiling status scores of body mass index, physical activity, alcohol consumption, the Dietary Approaches to Stop Hypertension diet, and the use of non-narcotic analgesics. We documented 12,588 incident cases of hypertension during 20 years of follow-up. The risk of hypertension associated with a combination of low birth weight at term and unhealthy lifestyle factors (RR, 1.95; 95 % CI, 1.83-2.07) was more than the addition of the risk associated with each individual factor, indicating a significant interaction on an additive scale (P interaction <0.001). The proportions of the association attributable to lower term birth weight alone, unhealthy lifestyle alone, and their joint effect were 23.9 % (95 % CI, 16.6-31.2), 63.7 % (95 % CI, 60.4-66.9), and 12.5 % (95 % CI, 9.87-15.0), respectively. The population-attributable-risk for the combined adulthood unhealthy lifestyle and low birth weight at term was 66.3 % (95 % CI, 56.9-74.0). The majority of cases of hypertension could be prevented by the adoption of a healthier lifestyle, though some cases may depend on simultaneous improvement of both prenatal and postnatal factors.