Background: Few if any studies have assessed the relationship between birth weight and incident atrial fibrillation (AF).
Methods and results: From 1993 to 2009, we prospectively followed 27 982 women who were >45 years of age and free of cardiovascular disease and AF at baseline. Information on birth weight was categorized into 5 different categories: <2.5, 2.5 to 3.2, 3.2 to 3.9, 3.9 to 4.5, and >4.5 kg. The primary outcome was time to incident AF. During 14.5 years of follow-up, 735 AF events occurred. Age-adjusted incidence rates for incident AF from the lowest to the highest birth weight category were 1.45, 1.82, 1.88, 2.57, and 2.55 events per 1000 person-years of follow-up. After multivariable adjustment, hazard ratios for incident AF across increasing birth weight categories were 1.0, 1.30 (95% confidence interval [CI], 0.96 to 1.75), 1.28 (95% CI, 0.96 to 1.69), 1.70 (95% CI, 1.23 to 2.37), and 1.71 (95% CI, 1.12 to 2.61) (P for linear trend=0.002). Adding body mass index, blood pressure, and diabetes mellitus at study entry did not have a large effect on these estimates (P for linear trend=0.004). In contrast, including height in the multivariable model substantially attenuated the relationship between birth weight and AF (P for linear trend=0.17), and additional adjustment for maximum weight in young adulthood further attenuated this association (multivariable-adjusted hazard ratio across birth weight categories, 1.0, 1.27 [95% CI, 0.94 to 1.71], 1.10 [95% CI, 0.83 to 1.46], 1.41 [95% CI, 1.01 to 1.96], and 1.29 [95% CI, 0.84 to 1.98]; P for linear trend=0.23).
Conclusions: Birth weight is significantly associated with incident AF among women, suggesting that early life determinants may play an important role in the pathogenesis of AF.
Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000479.