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9th September 2021
It is well established that physical activity is associated with health benefits such as a lower risk of coronary heart disease, stroke and type 2 diabetes. One widely accepted means of quantifying physical activity is the number of steps/day although this metric is not generally included in national physical activity guidelines. However, while a 2019 review noted an inverse relationship between daily steps and positive health outcomes such as all-cause mortality and cardiovascular events, it concluded that more independent studies are required before these observations can be translated into public health guidelines. This is despite a 2020 review concluding that walking an additional 1000 steps/day can help lower the risk of all-cause mortality and cardiovascular disease morbidity. In addition, while there is some evidence that an increased intensity of physical activity is associated with greater health benefits, it is unclear whether the number of steps/day and step intensity positively impact on mortality.
In trying to establish whether both the number of steps/day and intensity affected mortality, a team from the Institute for Applied Life Sciences, University of Massachusetts, US, conducted a prospective study in middle-aged Black and White adults. Participants were recruited from the Coronary Artery Risk Development in Young Adults (CARDIA) study which included a balanced sample by race (e.g., Black and White), sex, age and education levels from four different locations across the US. Participants were asked to wear an ActiGraph 72164, which measures the number of free-living steps/days, for 7 consecutive days during waking hours. Based on the number of recorded steps, participants were then grouped as low (<7000 steps/day), moderate (7000–10,000) and high (>10,000). They quantified step intensity as daily minutes at 100 steps/min or more, which indicates moderate intensity. The primary outcome was all-cause mortality and the results were adjusted for several covariates including smoking status, race, body mass index, alcohol intake and a measure of diet, the healthy eating index.
There were 2110 participants recruited with a mean age of 45.2 years (57.1% female), of whom 42.1% were of Black ethnicity. Individuals were followed-up for a period of 20 years. Compared with those in the low step group, there was a significantly lower mortality in those in the moderate group (adjusted hazard ratio, aHR = 0.28, 95% CI 0.15 – 0.54). Interestingly, among those taking a higher number of steps/day, the reduction in risk was less (aHR = 0.45, 95% CI 0.25 – 0.81), indicating no potential mortality benefit from taking more than 10,000 steps/day.
Subgroup analysis revealed no difference in risk reductions among Black (aHR = 0.30) or White participants (aHR = 0.37), for those in the moderate step groups or between the sexes, aHR = 0.28 (women) and aHR = 0.42 (men). Furthermore, the step intensity did not affect mortality estimates.
The authors concluded that taking at least 7,000 steps/day during middle-age was associated with a lower mortality risk but that step intensity had no impact.
Paluch AE et al. Steps per Day and All-Cause Mortality in Middle-aged Adults in the Coronary Artery Risk Development in Young Adults Study. JAMA Netw Open 2021