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Comment on ‘Association of Physical Activity Intensity with Mortality. A National Cohort Study of 403 681 US Adults’ published in JAMA Internal Medicine (doi: 10.1001/jamainternmed.2020.6331)

Key Points

  • This cohort study explored the association of the proportion of vigorous physical activity (VPA) to total physical activity [defined as moderate to vigorous physical activity (MVPA)] with all-cause, cardiovascular disease (CVD), and cancer mortality.1 Data on self-reported physical activity of a cohort of 403 681 individuals [52% women; mean (SD) age, 42.8 (16.3) years] from the National Health Interview Survey (NHIS) study, conducted by the US Centers for Disease Control and Prevention, were linked to the National Death Index records: 36 861 deaths occurred, including 7634 from CVD and 8902 from cancer, during a median follow-up of 10.1 years.

  • Leisure-time physical activity was measured with two sets of questions addressing frequency and duration of light or moderate physical activity (MPA) and VPA; the total amount of MPA and VPA was calculated by multiplying frequency and duration. Less than 50% of the participants met the physical activity guidelines and about one-third had no MVPA.

  • For the same amount of total physical activity, participants with a greater proportion of VPA to MPA had lower all-cause mortality. For instance, among participants doing any MVPA, more than 50–75% of VPA to total physical activity was associated with 17% lower all-cause mortality.

  • In contrast, the study did not find a consistent inverse association of proportion of VPA with CVD and cancer mortality. Participants performing 150–299 min per week of MPA and 150 min per week or more of VPA had the lowest all-cause mortality risk.

  • These results support the hypothesis that VPA is associated with greater mortality risk reduction compared with MPA.

Comment

Among protective lifestyle interventions, physical activity has been demonstrated to reduce all-cause and CVD mortality in healthy individuals by 20–30% in a dose–response fashion.2 Thus, although any physical activity is better than none and sedentary behaviour is deadly for the heart, ideally, physical activity should be dosed in modality, duration, frequency, and volume, similar to drug therapy. Recently released World Health Organization (WHO) guidelines on physical activity and sedentary behaviour3 updated the weakly target range of the previous guidelines4 from at least 150 min to 150–300 min of MVPA, and from at least 75 min to 75–150 min of VPA, based on initial data that VPA is associated with higher health benefit than MVPA.5 The present study conducted in a large, representative sample of US adults, provides data to support the association of VPA with greater mortality risk reduction compared with MPA.1 Interestingly, the WHO newly recommended target for weekly MVPA and VPA3 was associated with the lowest all-cause mortality in the NHIS cohort.1

On the other hand, the present study did not find a consistent inverse association of proportion of VPA with CVD and cancer mortality, raising questions about the mechanism(s) underlying the health benefits of VPA. These have been attributed in the past to overall improvements in peak oxygen consumption, cardiac stroke volume, blood pressure, body composition, and lipid profiles.1

In addition to residual confounding that cannot be excluded, as in all observational studies, the main limitation of the present study is represented the modality of physical activity reporting, which was based on questionnaires, compiled one point in time by each participant, in which vigorous leisure-time physical activities are defined qualitatively as those causing ‘heavy sweating or large increases in breathing or heart rate’. Recently published quantitative data, gathered from wrist-worn accelerometers, showed the correlation between all-cause mortality risk and physical activity energy expenditure (PAEE) and the proportion of expenditure undertaken in MVPA.6 In this cohort of 500 000 UK Biobank participants, higher volumes of PAEE were associated with reduced mortality rates, and achieving the same volume through higher-intensity activity was associated with greater mortality reductions than through lower-intensity activity.6

In conclusion, the unanimous public health message that comes from the present study,1 other contemporary studies6 and guidelines3,7 is that although most of the health benefit associated with achieving currently recommended physical activity goals may be obtained through MPA, the available evidence suggests that an increased proportion of VPA to total physical activity is associated with greater mortality risk reduction.

Conflict of interest: L.G. has no conflict of interest. C.P. reports personal fees from Acticor Biotech, personal fees from Amgen, personal fees from Bayer, personal fees from GlaxoSmithKline, personal fees from Tremeau, personal fees from Zambon, grants from AIFA (Italian Drug Agency), grants from European Commission, other from Scientific Advisory Board of the International Aspirin Foundation, outside the submitted work.