Long-term obesity and BMI change associated with increased risk for AF

Weight and weight change and risk of atrial fibrillation: the HUNT study

Literature - Feng T, Vegard M, Strand LB et al., - Eur Heart J. 2019; 40(34): 2859-2866. https://doi.org/10.1093/eurheartj/ehz390

Introduction and methods

The associations between obesity and AF risk are well established [1,2]. The incidence and prevalence of both conditions have risen substantially worldwide, with an accompanying rise in the burden on the medical system. Thus, a better understanding of risk factors for AF is needed.

Research on the link between obesity and AF often use measures for height and weight at a single timepoint, which do not account for the cumulative effect of obesity over the course of AF development, nor for the impact of long-term obesity or weight change. Some studies have used self-reported current and recalled earlier body weight, of which the latter is known to be inaccurate [3-5]. Studies that did use repeated body weight measurements, were limited by small sample size [3,6], short time intervals between measurements [4,6-8] or missing information on important covariates like comorbidity [3,4,6,7].

This large population-based study investigated the cumulative effects of obesity and weight change on AF risk over four decades. Repeated measurements of weight and height were used, as well as verified AF diagnoses and information on a wide range of CV risk factors was available. All 93,860 residents of at least 20 years old in a Norwegian County were invited to participate in HUNT-3 [8], from October 2006 to June 2008. 50,804 Inhabitants (54%) filled out questionnaires and underwent baseline clinical examinations. Height and weight information was also available from a mandatory tuberculosis screening conducted between 1966 and 1969, and from HUNT-1 and HUNT-2. 15,214 Individuals had information from all three previous measurements and were included in the main analysis.

Main results

  • Current BMI was not strongly associated with the risk of AF, after adjustment for average BMI earlier in life. Average BMI earlier in life was associated with AF risk in overweight (HR: 1.2, 95%CI: 1.0-1.5) and obese individuals (HR: 1.6, 95%CI: 1.1-2.2) compared to those with normal weight, even after adjustment for BMI at the beginning of follow-up.

BMI change and risk of AF

  • Those with loss or gain in BMI showed a higher AF risk, although not all hazards were significantly different from the references group with stable BMI (-2.5 to 2.5 change).
  • The greatest risk increase was seen in those with ≥5 BMI points increase (HR: 2.6).
  • Hazards were calculated for the early (1967-1985), middle (1985-1996) and late periods (1996-2007) and the highest (numerical) risks were seen in late periods. Correction for most recent BMI weakened the association of BMI loss, while that of BMI gain and AF was mostly unchanged.

Other body mass measures and risk of AF

  • The highest vs. lowest degree of weight variability was associated with a higher risk of AF (HR: 1.5, 95%CI: 1.2-1.8). Average waist circumference (WC) >88/102 cm also associated with higher AF risk (HR: 1.2, 95%CI: 1.1-1.4) compared with those below this cut-off. The effects disappeared after adjustment for BMI.
  • Average waist-hip ratio (WHR), change in WC or change in WHR were not associated with AF risk.

Conclusion

This large population-based study shows that long-term obesity and BMI change were associated with increased AF risk, also after accounting for current BMI. This underscores the relevance of considering weight history when assessing AF risk, rather than only considering current weight.

Editorial comment

Middeldorp and colleagues [10] emphasize the global epidemic of obesity, and note that studies have mostly focused on older populations with obesity. There is growing recognition of primary prevention and the importance of long-term exposure to risk factors. This is relevant in the context of the fact that obesity is now also alarmingly prevalent in childhood.

A central strength of the study by Feng et al. is the availability of weight data over a 40 year period. With this data, the authors demonstrate that cumulative BMI over an extended period is a superior predictor of AF risk, compared to a single measurement, even though the latter may be more recent. This may not only be an effect of BMI earlier in life, as the authors postulate, but can also reflects the greater risk associated with longer exposure. These long-term observational data complement insights obtained in mendelian randomization studies.

The data on abdominal adiposity may seem confusing at first, as WC was associated with AF development but not WHR or change in either measurements. Middeldorp et al. find a possible explanation in a meta-analysis reporting risk estimates for different adiposity measurements and AF. The totality of observational data suggests that associations with AF appear strongest for WC and BMI. And more accurate quantification of adiposity may result in even stronger associations.

Among the limitations of the study are the fact that AF type (paroxysmal or persistent) was not available, and that the data points did not account for asymptomatic, or minimally symptomatic or subclinical groups of AF, which are increasingly recognized as important clinical entities. Moreover, it did not account of other time-varying risk factors that can contribute to AF.

In conclusion, the study by Feng et al. greatly advances our knowledge on the importance of long-term exposure to weight, weight gain and weight fluctuation for AF risk. Weight reduction and aggressive risk factor management strategies have been shown to improve AF outcomes in obese individuals. Efforts to address established obesity should be increased, and the complex mechanisms underpinning obesity and arrhythmogenesis should be unraveled, to refine our management approach to help these patients.

References

1. Aune D, Sen A, Schlesinger S, et al. Body mass index, abdominal fatness, fat mass and the risk of

atrial fibrillation: a systematic review and dose–response meta-analysis of prospective studies. Eur J Epidemiol 2017;32:181–192.

2. Feng T, Vegard M, Strand LB, et al. Metabolically healthy obesity and risk for atrial fibrillation: the HUNT study. Obesity (Silver Spring) 2019;27:332–338.

3. Rosengren A, Hauptman PJ, Lappas G, et al. Big men and atrial fibrillation: effects of body size and weight gain on risk of atrial fibrillation in men. Eur Heart J 2009;30:1113–1120.

4. Tedrow UB, Conen D, Ridker PM, et al. The long- and short-term impact of elevated body mass index on the risk of new atrial fibrillation: the WHS (Women’s Health Study). J Am Coll Cardiol 2010;55:2319–2327.

5. Dahl AK, Reynolds CA. Accuracy of recalled body weight—a study with 20-years of follow-up. Obesity (Silver Spring) 2013;21:1293–1298.

6. Johnson LS, Juhlin T, Engström G, et al Risk factor changes and incident atrial fibrillation among middle-aged men in the Malmo¨ Preventive Project cohort. Eur Heart J Cardiovasc Pharmacother 2016;2:81–87.

7. Huxley RR, Misialek JR, Agarwal SK, et al. Physical activity, obesity, weight change and risk of atrial fibrillation: the Atherosclerosis Risk in Communities (ARIC) study. Circ Arrhythm Electrophysiol 2014;7:620–625.

8. Norby FL, Soliman EZ, Chen LY, et al. Trajectories of cardiovascular risk factors and incidence of atrial fibrillation over a 25-year follow-up: the ARIC study (Atherosclerosis Risk in Communities). Circulation 2016;134:599–610.

9. Holmen J, Midthjell K, Krüger Ø, et al. The Nord-Trøndelag Health Study 1995–97 (HUNT 2): objectives, contents, methods and participation. Norsk Epidemiol 2003;13: 19–32.

10. Middeldorp M, Wong CX, Gallagher C et al., No time to weight: obesity through life and AF risk. Eur Heart J. 2019; 40(34): 2867-2869

Find this article online at Eur Heart J.

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