Dose-Response Relationship of Physical Activity to Premature and Total All-Cause and Cardiovascular Disease Mortality in Walkers

Purpose

To assess the dose-response relationships between cause-specific mortality and exercise energy expenditure in a prospective epidemiological cohort of walkers.

Methods

The sample consisted of the 8,436 male and 33,586 female participants of the National Walkers'' Health Study. Walking energy expenditure was calculated in metabolic equivalents (METs, 1 MET = 3.5 ml O₂/kg/min), which were used to divide the cohort into four exercise categories: category 1 (≤1.07 MET-hours/d), category 2 (1.07 to 1.8 MET-hours/d), category 3 (1.8 to 3.6 MET-hours/d), and category 4 (≥3.6 MET-hours/d). Competing risk regression analyses were use to calculate the risk of mortality for categories 2, 3 and 4 relative to category 1.

Results

22.9% of the subjects were in category 1, 16.1% in category 2, 33.3% in category 3, and 27.7% in category 4. There were 2,448 deaths during the 9.6 average years of follow-up. Total mortality was 11.2% lower in category 2 (P = 0.04), 32.4% lower in category 3 (P<10⁻¹²) and 32.9% lower in category 4 (P = 10⁻¹¹) than in category 1. For underlying causes of death, the respective risk reductions for categories 2, 3 and 4 were 23.6% (P = 0.008), 35.2% (P<10⁻⁵), and 34.9% (P = 0.0001) for cardiovascular disease mortality; 27.8% (P = 0.18), 20.6% (P = 0.07), and 31.4% (P = 0.009) for ischemic heart disease mortality; and 39.4% (P = 0.18), 63.8% (P = 0.005), and 90.6% (P = 0.002) for diabetes mortality when compared to category 1. For all related mortality (i.e., underlying and contributing causes of death combined), the respective risk reductions for categories 2, 3 and 4 were 18.7% (P = 0.22), 42.5% (P = 0.001), and 57.5% (P = 0.0001) for heart failure; 9.4% (P = 0.56), 44.3% (P = 0.0004), and 33.5% (P = 0.02) for hypertensive diseases; 11.5% (P = 0.38), 41.0% (P<10⁻⁴), and 35.5% (P = 0.001) for dysrhythmias: and 23.2% (P = 0.13), 45.8% (P = 0.0002), and 41.1% (P = 0.005) for cerebrovascular diseases when compared to category 1.

Conclusions

There are substantial health benefits to exceeding the current exercise guidelines.