The long- and short-term impact of elevated body mass index on the risk of new atrial fibrillation the WHS (women's health study)

Abstract

Objectives: The purpose of this study was to characterize the relationship between changes in body mass index (BMI) and incident atrial fibrillation (AF) in a large cohort of women.

Background: Obesity and AF are increasing public health problems. The importance of dynamic obesity-associated AF risk is uncertain, and mediators are not well characterized.

Methods: Cases of AF were confirmed by medical record review in 34,309 participants in the Women's Health Study. Baseline and updated measures of BMI were obtained from periodic questionnaires.

Results: During 12.9 +/- 1.9 years of follow-up, 834 AF events were confirmed. BMI was linearly associated with AF risk, with a 4.7% (95% confidence interval [CI]: 3.4 to 6.1, p < 0.0001) increase in risk with each kilogram per square meter. Adjustment for inflammatory markers minimally attenuated this risk. When updated measures of BMI were used to estimate dynamic risk, overweight (hazard ratio [HR]: 1.22; 95% CI: 1.02 to 1.45, p = 0.03), and obesity (HR: 1.65; 95% CI: 1.36 to 2.00; p < 0.0001) were associated with adjusted short-term increases in AF risk. Participants becoming obese during the first 60 months had a 41% adjusted increase in risk of the development of AF (p = 0.02) compared with those maintaining BMI <30 kg/m(2). The prevalence of overweight and obesity increased over time. The adjusted proportion of incident AF attributable to short-term elevations in BMI was substantial (18.3%).

Conclusions: In this population of apparently healthy women, BMI was associated with short- and long-term increases in AF risk, accounting for a large proportion of incident AF independent of traditional risk factors. A strategy of weight control may reduce the increasing incidence of AF. (Women's Health Study [WHS]: A Randomized Trial of Low-Dose Aspirin and Vitamin E in the Primary Prevention of Cardiovascular Disease and Cancer; NCT00000479).

Figure 1

Survival free of atrial fibrillation by BMI category. Shown is an age-adjusted Kaplan Meier survival curve plotting survival free of atrial fibrillation divided into categories of BMI (Normal < 25 kg/m2, Overweight 25–30 kg/m2, and Obese ≥ 30 kg/m2). The log rank test shows statistical significance with a p value of < 0.0001.

Figure 2

Incident AF and Percent of women in each WHO Category over 3 Year Time Periods. Shown is a bar graph of the percent of women in each WHO category at the beginning of four 36 month time periods over the course of the study. The incidence rate of AF (per 1000 participants per period) for each 36 month time period is superimposed on the graph for comparison.

Figure 3

Overweight and Obesity and risk of incident atrial fibrillation, stratified by various baseline characteristics Shown are hazard ratios for incident AF stratified by various baseline characteristics. The number of patients in each category is indicated in the first column. Hazard ratios and 95% confidence intervals are shown on a logarithmic scale with overweight in black and obese in green. All hazard ratios are adjusted for adjusted for age, race, vitamin E, beta carotene, aspirin use, diabetes, hypertension (defined as self-reported systolic blood pressure of ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg, or report of diagnosis of hypertension by a physician), history of hypercholesterolemia (self-reported cholesterol of at least 240 mg/dl (6.22 mmol/l)), diabetes, alcohol consumption (rarely/never, <1 drink per week, 1 to 6 drinks per week, ≥1 drink per day), smoking (never, past, current), and physical activity (< 1000 kilocalories per week, ≥ 1000 kilocalories per week)