Change in Cardiorespiratory Fitness and Risk of Stroke and Death: Long-Term Follow-Up of Healthy Middle-Aged Men

Abstract

Background and Purpose- Low cardiorespiratory fitness is associated with increased risk of cardiovascular disease. The present study aims to assess whether change of fitness over time has any impact on long-term risk of stroke and death. Methods- We recruited healthy men aged 40 to 59 years in 1972 to 1975, and followed them until 2007. Physical fitness was assessed with a bicycle ECG test at baseline and again at 7 years, by dividing the total exercise work by body weight. Participants were categorized as remained fit, became unfit, remained unfit, or became fit, depending on whether fitness remained or crossed the median values from baseline to the 7-year visit. Outcome data were collected up to 35 years, from study visits, hospital records, and the National Cause of Death Registry. Risks of stroke and death were estimated by Cox regression analyses and expressed as hazard ratios (HRs) with 95% CIs. Results- Of 2014 participants, 1403 were assessed both at baseline and again at 7 years, and were followed for a mean of 23.6 years. Compared with the became unfit group, risk of stroke was 0.85 (0.54-1.36) for the remained unfit, 0.43 (0.28-0.67) for the remained fit, and 0.34 (0.17-0.67) for the became fit group. For all-cause death, risks were 0.99 (0.76-1.29), 0.57 (0.45-0.74), and 0.65 (0.46-0.90), respectively. Among those with high fitness at baseline, the became unfit group had a significantly higher risk of stroke (HR, 2.35; CI, 1.49-3.63) and death (HR, 1.74; CI, 1.35-2.23) than those who remained fit. Among those who had low fitness at baseline, the became fit group had a significantly lower risk of stroke (HR, 0.40; CI, 0.21-0.72) and death (HR, 0.66; CI, 0.50-0.85) than participants in the remained unfit group. Conclusions- Cardiorespiratory fitness at baseline and change in fitness was associated with large changes in long-term risk of stroke and death. These findings support the encouragement of regular exercise as a stroke prevention strategy.

Keywords: cause of death; exercise; physical fitness; risk factors; stroke.