Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia and imparts substantial burden. Prevalence is increasing in parallel with aging, improved survival and emerging epidemics of antecedent risk factors. Body mass index (BMI) is a validated risk factor for incident AF. However, the impact of BMI (including change over time) on the risk of AF in the different sexes has not been fully elucidated.
Methods: The Tromsø Study (Norway) is a longitudinal population study consisting of seven surveys conducted from 1974 to 2016. We used data collected at the second (1979-1980), third (1986-1987) and fourth (1994-1995) surveys. AF diagnosis (collected to 2013) was derived from hospital record linkage. Cox regression analysis was conducted using fractional polynomials of BMI, BMI change and age with all models adjusted for CVD risk factors, co-morbidities and antihypertensive drug use.
Results: Data were available for 24,843 individuals from the fourth Tromsø survey (mean age 45.5 ± 14.2 years, 52.9% female). Over a mean follow-up of 15.9 ± 5.4 years, n = 581 (4.4%) women and n = 595 (5.1%) men developed AF. In men, lower BMI was associated with a decreased risk of AF and higher BMI was associated with an increased risk (HR, 95% CI for BMI 18 kg/m2 was 0.83, 0.78-0.89; for BMI 40 kg/m2 was 4.49, 2.63-7.68, when BMI 23 kg/m2 used as a reference). The same pattern was identified in women although associations were not as strong. Of the three surveys, 17,367 individuals attended at least two. In men, a decrease in BMI over 10 years was associated with a decreased risk of AF and an increase in BMI increased the risk of AF development (HR, 95% CI for 2 kg/m2 decrease in BMI was 0.86, 0.75-0.99; for 4 kg/m2 increase in BMI was 1.26, 1.02-1.55, when 1 kg/m2 increase in BMI used as a reference). No associations between change in BMI and risk of AF were identified in women.
Conclusions: Within a population cohort, higher BMI was significantly and independently associated with an increased risk of future AF although this was stronger for men compared to women. Changes in BMI over time influenced the risk of AF in men but not women. Weight maintenance/reduction strategies should potentially be different for women and men but should form part of a lifetime approach to the primary prevention of AF.