ArticlesMinimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study
Introduction
Much evidence suggests that 150 min or more a week of leisure-time physical activity (LTPA) can have substantial health benefits for an individual.1, 2 Guidelines such as the 2008 physical activity guidelines for Americans1 and WHO's 2010 Global Recommendations on Physical Activity for Health1, 3 have drawn attention to the health benefits of this amount of weekly exercise. Because barriers exist to meet this 30 min a day, 5 day a week recommendation (eg, time constraints or an individual's uncertainty about the amount of exercise needed to benefit health), LTPA is an underused public health intervention. East Asians tend to be less physically active than individuals in western countries, and also tend to exercise at lower intensity.4, 5 A third of the American adult population met this recommendation,1 whereas less than a fifth of the adult population did in East Asian countries such as China, Japan, or Taiwan.4, 5 Whether levels of physical activity below the recommended 150 min a week are adequate to generate health benefits is unclear.
Identification of a minimum amount of exercise—or minimum dose1—sufficient to reduce mortality is desirable because a small amount of exercise can be easier to achieve. Furthermore, patients might be more easily motivated to exercise if their doctor recommends an easily manageable amount, especially if health messages are simple. Because east Asians visit their doctors frequently,6 plenty of opportunities for health communication and prescription of exercise exist.7 However, such opportunities to prescribe exercise are sometimes missed because most doctors are expected to treat only diseases, having little time to modify a behaviour that is not directly related to the disease if not requested by a patient. If health-enhancing physical activity were to be prescribed, it should be related to the disease in question, and the recommended amount should be kept to a minimum to increase the chances of adherence.
The objective of this study is to assess the health benefits of different volumes of physical activity in a large cohort in Taiwan, and to investigate whether less than 150 min a week of exercise is sufficient to reduce mortality or extend life expectancy.
Section snippets
Data collection
In this historically prospective cohort study, the cohort consisted of 416 175 healthy individuals aged 20 years or older (199 265 men and 216 910 women) who participated in a standard medical screening programme run by a private firm (MJ Health Management Institution, Taipei, Taiwan)—all participants were followed up between 1996 and 2008.8 The 13-year study period yielded 3·35 million person-years of follow-up, with an average follow-up of 8·05 years (SD 4·21). Every individual's
Results
Table 1 shows the proportion of individuals in each LTPA volume category and selected characteristics of all individuals in the cohort. Table 2 shows activity characteristics (duration, intensity, volume, and energy expenditure) for each LTPA volume category (webappendix p 2 shows mean activity characteristics by sex and age groups).
Compared with individuals in the low-volume activity group, those in the inactive group had a 17% increased all-cause mortality risk (HR 1·17, 95% CI 1·10–1·24) and
Discussion
Individuals who did a daily average of 15 min of moderate-intensity exercise had significant health benefits when compared with individuals who were inactive. In Taiwan, if inactive individuals engage in low-volume daily exercise, one in six all-cause deaths could be postponed—mortality reductions of similar magnitude have been estimated for a successful tobacco control programme in the general population.16 The minimum amount of exercise reported in this study is half of that recommended
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These authors shared first authorship