Åberg ND, Kuhn HG, Nyberg J, Waern M, Friberg, P Svensson J, et al. Influence of Cardiovascular Fitness and Muscle Strength in Early Adulthood on Long-Term Risk of Stroke in Swedish Men. Stroke. 2015
We always tell our patients to exercise in order to decrease their risk of stroke. But is there really strong data to support it? Most of it is based on data from self-reporting and not really focused on young people followed long term to look at prevention.
A Swedish group followed a cohort of over 1.6 million young men from the 60s through the early 2000s for 5-42 years. They tested their isometric muscle strength and fitness (cycle ergometric testing to assess cardiovascular fitness) at age 18 when they were drafted for military duty and divided each of these measures into tertiles of intensity. They then looked at their hospital discharge summaries over the years to capture their first stroke. They found a dose responsive and independent relationship between more exercise or muscle strength and less strokes of any type (ischemic, ICH, or SAH). This association remained for each of the 3 subgroups of stroke, but was highest for ICH. Fitness remained an independent association for lower stroke risk when adjusted for muscle strength. This was not the case when muscle strength was adjusted for fitness. So it seems that fitness in young , Swedish men, which typically is associated with increased muscle strength, is inversely proportional to risk of stroke of all kinds.
For the lowest tertile of fitness, the HR was 1.7 for all strokes and 2.52 for fatal stroke
For the lowest tertile of muscle strength, the HR was 1.39 for all strokes
Limitations of this study include the absence of women, the elderly, and being limited to Swedes. It also assessed patients’ baseline fitness and strength which could be related to their genetic fitness and not necessarily anything they have control over. We don’t’ have data on how fit they were or how other lifestyle demographics changed over the years after their initial assessments. There is also selection bias as patients with certain medical conditions may have been excused from military duty.
How does this study change my practice?
I could cite data when counseling patients on exercise for the prevention of stroke, even though it’s common sense. More importantly, I could direct neurology residents and medical students to this data for their education and future research.