Even low amounts of exercise are beneficial
Author: Louise Prime
Even low levels of leisure-time physical activities are beneficial for adults, although doing more vigorous exercise has additional health benefits in terms of reducing mortality, according to a study* in the British Journal of Sports Medicine. The authors called for the promotion of any amount and intensity of physical activity, to reduce mortality risk in the general population.
The research team, from China and the US, analysed US data from 12 cross-sectional waves of the National Health Interview Surveys (NHIS) during 1997–2009, covering 88,140 eligible participants aged 40–85 years in the US, which they linked to the National Death Index records for mortality up to 31st December 2011.
Study participants had answered two sets of questions to assess their frequency and duration of leisure time physical activity; physical activity (of at least 10 minutes) was categorised as vigorous (for example running, faster cycling and competitive sports, etc.) and light or moderate (eg, brisk walking, dancing and gardening, etc.). The researchers used a combination of frequency (times/week) and duration (minutes/time) to define leisure time physical activity as measured in minutes/week units.
Their analysis showed that, when adjusted for all study covariates, participants performing 10–59 min/week of leisure time physical activity had 18% lower risk of all-cause mortality (hazard ratio, HR 0.82) compared with physically inactive participants. People who reported 1–2 times (150–299 min/week) the recommended level of leisure time physical activity had 31% reduced risk of all-cause mortality (HR 0.69).
They noted that until now it has been unclear whether or not there is a potential harm resulting from excessive physical activity, i.e. a greater number of hours more than the recommended. But their results found there were further benefits among those performing leisure time physical activity 10 or more times (≥1500 min/week) the recommended minimum level (HR 0.54). For 10–59, 150–299 and ≥1500 min/week of physical activity, the corresponding HRs for cardiovascular disease (CVD)-specific mortality were 0.88, 0.63 and 0.67, respectively; and for cancer-specific mortality were 0.86, 0.76) and 0.53, respectively. There was a larger reduction in all-cause and cause-specific mortality for vigorous vs. moderate intensity physical activity.
The researchers noted that, currently, about 51% US adults fail to meet the recommendation for physical activity, and they commented: “Using a nationally representative sample of US adults, our study suggested that individuals with 10–59 min/week of light-to-moderate physical activity had significant health benefits compared with physically inactive adults. Individuals with high levels of physical activity could achieve further health benefits. Importantly, very high levels of physical activity (10 or more times than the recommended minimum by the physical activity guidelines) continued to have health benefits against mortality risk.”
They noted several possible limitations of their study, including recall bias in respondents’ answers, unaccounted-for confounders, and lack of data on either sedentary time, non-leisure physical activity or activity levels during follow-up.
But they concluded: “Assuming causality of the associations we observed, both low and high levels of [physical activity] have beneficial effects on all-cause and cause-specific mortality risk. Importantly, vigorous [physical activity] has added benefits for reducing mortality compared with moderate [physical activity]. Promoting [physical activity] of any intensity and amount is an important approach to reducing mortality risk in the general population.”
*Zhao M, Veeranki SP, Li S, et al. Beneficial associations of low and large doses of leisure time physical activity with all-cause, cardiovascular disease and cancer mortality: a national cohort study of 88,140 US adults. Br J Sports Med Epub ahead of print: 19 March 2019. doi:10.1136/bjsports-2018-099254.