Alert & Oriented

Note: paternity-related editorial delay…

This paper is yet another report from the Physician’s Health Study, a very large and very old clinical trial/prospective cohort study that followed some 22,000 physicians by questionnaire administered at various time points.  One initial aim of the study was to test any mortality benefit of some primary prevention measures (daily aspirin, beta-carotene), but enough data was collected that numerous other associations (or lack of) have been reported over the years.  This particular report looked at the association between responses to exercise questionnaires administered at the 3-year and 9-year time points in the study, and subsequent development of atrial fibrillation (self-reported).

Again, these data mining efforts are always difficult to interpret.  Quite a bit of effort was put into adjusting for confounders for the development of AF, including alcohol intake, BMI, etc.  Three multi-variable models were tested and the statistical analysis is mind-numbing, as expected.  In addition to controlling for variables, they had to look at answers to risk factors and exercise questionnaires at various time points and adjust the analysis accordingly, since not all who were exercising vigorously at first necessarily kept up the lifestyle later one, etc.

There were enough participants that the level of exercise could be categorized into several buckets.  The referent group were the non-exercisers. Note that they treated frequency of exercise as a continuous variable and assigned the ‘mid-point’ value between the response to the 3-year questionnaire and to the 9-year questionnaire.  Adjustments of that sort are inevitable in these kinds of study, but naturally they impact the realism of the model.

A relationship between exercise and risk of AF could be found only in the “regular vigorous” group, .e. those who broke a sweat with exercise and exercised 5-7 days a week.  If those were divided according to sporting activity (those who practice more than one activity were excluded), a significant relationship could only be found among the joggers.

For the joggers in the study, the main findings are in the graph below:

Click to enlarge

For the group of vigorous exercisers as a whole, a relationship between AF risk and exercise was somewhat stronger if one looked at participants who were younger than 50 at entry.

Take Home:  This study adds a little bit to the evidence linking chronic vigorous exercise to risk of AF.  No new aspects of that relationship are revealed.