Role of physical fitness in the obesity paradox. Long-term major adverse cardiovascular events in the Women's Ischemia Syndrome Evaluation (WISE)

Abstract

Abstract Background Emerging data suggests there is an “obesity paradox” where obesity may be protective against cardiovascular morbidity and mortality in patients with cardiovascular disease. However, weight status primarily assessed through body mass index (BMI) is limited in its ability to discern contributions from fat vs. lean muscle mass. Most studies on BMI have not accounted for physical fitness, which is a known modifier of weight status and a potential mediator of effects of obesity on major adverse cardiovascular events (MACE). Purpose To investigate the relationship between BMI and physical fitness, measured by self-reported Duke Activity Status Index (DASI) score, with long-term MACE in women evaluated for suspected myocardial ischemia. Methods The National Heart, Lung, and Blood Institute Women's Ischemia Syndrome Evaluation (WISE) study is a multicenter prospective cohort study. From 1996–2000, 936 women were enrolled at the time of clinically indicated coronary angiography and assessed with a median follow up of 5.8 (range 0–9 years) for MACE. MACE was defined as a composite of death, nonfatal myocardial infarction, stroke, or congestive heart failure. Proportional hazards regression was used to estimate adjusted hazard ratios of MACE in relation to metabolic status and physical fitness. DASI scores ≥25, equivalent to ≥7 metabolic equivalents [METs]) was used as cut point to define high physical fitness, in our prior studies DASI >25 approximates completion of the second stage of a Bruce treadmill protocol. Results Among the 899 women with complete data, 69.5% had low physical fitness (DASI scores <25), 34.9% overweight (BMl ≥25 to 30), 40.5% obese (BMI ≥30). In fit women, obesity was associated with lower hazard ratio for MACE (HR 0.64, p=0.01); while low fitness in normal weight women was associated with 60% excess risk of MACE (HR 1.61, p=0.01) (Figure 1). Conclusions Among women undergoing coronary angiography for suspected myocardial ischemia, obesity was inversely related with long-term MACE in physically fit women. Our findings suggest that physical fitness may play a role in the obesity paradox. These results support the inclusion of fitness in understanding the relations between body weight and long-term MACE. The DASI is a simple, self reported tool that can identify higher-risk symptomatic women and should be considered in future investigations and routine examination of normal, overweight and obese women. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): U01 HL064829