Commentary: Lisa Rooke, National Heart Foundation of Australia
Walking is the most popular type of physical activity undertaken by people around the world. As a low-cost, low-impact activity accessible to most groups across the age spectrum, it’s easy to understand why.
The health benefits of moderate or vigorous-intensity physical activity (MVPA) are well documented to include reduced risk of cardiovascular disease, type 2 diabetes, stroke, and breast and colon cancers. However, few recent reviews have examined associations between walking specifically and total mortality. This study from the United States (US) sought to document this in a large cohort of older adults aged 50 to 74 years (mean age 70.7 years).
The authors drew participants from a large prospective study of cancer patients from the Cancer Prevention Study (CPS)-II established in 1982 by the American Cancer Society. From this cohort of ~1.2 million participants, the study sample was drawn from the Nutrition Cohort, a subgroup that included 184,185 older adults of whom 77,077 were women, and 62,178 were men. Participants were drawn from across 21 US states with those aged over 90 years excluded from this study.
Participants of the CPS-II were mailed surveys every two years from 1997 with questions on demographics, medical information, and lifestyle factors. This analysis used the 1999 survey as baseline for exposure as more detail had been provided on physical activity than in previous surveys.
Physical activity was self-assessed on time spent per week in seven categories of activities, including walking, jogging, lap swimming, tennis, bicycling, aerobics and dancing. MET-hours/week were calculated using the ACSM Compendium of Physical Activities, then estimating the proportion meeting the Physical Activity Guidelines for American Adults of at least150 minutes of moderate-intensity or 75 minutes vigorous-intensity physical activity per week.
Walking was categorised in two ways. Firstly, for the main analysis, participants who engaged exclusively in walking were categorised as: insufficient or less than minimum recommended (<2-3 hours/week), sufficient or meeting the guidelines (4-6 hours/ week), or exceeding recommendations by two-fold (>6 hours/week). All other participants were categorised as either engaging in no MVPA (zero MET-hours/week) or any MVPA based on their total MET-hours/week (<8.75, 8.75–17.5, >17.5). The lowest level of walking (<2 hours/week) or activity served as the reference group in all analyses.
Statistically significant inverse associations were found between meeting or exceeding recommendations by walking only and all-cause mortality. Meeting the minimum recommendation (7.5-15 MET-hours/week) through walking only was associated with 20% lower risk of mortality. Exceeding recommendations through walking only was associated with a 29% lower all-cause mortality than those who were insufficiently active. Walking was associated with 23% lower risk of cardiovascular disease mortality.
Limitations of this study included lack of data related to occupational physical activity, using self-reported measures of physical activity, and that exposure information was not updated during follow-up. Furthermore, intensity was not assessed so participants may have walked at varied paces and on varying terrain.
Findings support previous meta-analyses that reported a range of 3% to 32% lowered risk of all-cause mortality from walking. and offer further insight into associations between walking for health in older adults. This research adds weight to the existing evidence base for the potential of significant public health impact in promoting walking specifically in this age group. In translating this research, interventions that promote walking as an activity in this age group should be accompanied by environmental supports that assist older walkers at a neighbourhood level.