Abstract 15300: Vigorous Physical Activity in the Women’s Health Initiative Cohort: Good or Maybe Not So Good?

Abstract

Introduction: Studies primarily of athletes have suggested that high levels of vigorous physical activity (PA) may increase the risk of amyotrophic lateral sclerosis (ALS). Case-control studies provide equivocal support for this hypothesis. Hypothesis: There have been no prior large cohort studies that have evaluated the relationship between vigorous PA, other risk factors, and subsequent ALS mortality among women. Methods: The Women’s Health Initiative (WHI), mean age of 63.6, assessed strenuous or hard PA, defined as PA that resulted in a sweat or fast heartbeat, at baseline by a self-administered questionnaire. Frequency of strenuous activity per week and duration in 20-minute intervals was collected. Metabolic equivalent (MET) intensity scores were then used to calculate the MET equivalence per week, similar to what had been used in previous WHI studies of PA. There were 165 women who were identified with ALS as the cause of death over an average 9.5 years follow-up. We excluded 4 deaths within 2 years of baseline evaluation. Results: Women who died from ALS were older and were predominantly white, n=145 (90%). Total hours of recreational PA was positively related to death due to ALS (p=.03) as was energy expenditure from strenuous activity (p=.045) and minutes of strenuous activity per week. In multivariate Cox models, duration of very hard or strenuous activity >40 minutes per week increased the hazards ratio of ALS, 1.67 (1.10-2.55, p=0.09 for trend), over time. Interestingly, the risk from performing no strenuous PA compared to some is similar in magnitude for total mortality [1.19 (1.12-1.27) based on 21,529 deaths], for CHD incidence [1.23 (1.10-1.37) based on 7,767 CHD events], and for breast cancer incidence [1.13 (1.03-1.25) based on 8,722 breast cancer deaths] in the WHI. Conclusions: This is the first cohort study that reported relationship of vigorous PA to risk of ALS even in sedentary participants. The protective effect of strenuous PA for total mortality, CHD, and breast cancer compared to the very small effect of strenuous PA on ALS risk does not compromise the overall benefit of vigorous exercise, but may provide an important clue as to the etiology of ALS.