LAUSR

Physical activity as an intervention at the individual level is now recognized as a valid countermeasure to reduce premature cardiovascular and all-cause mortality. Conversely, a sedentary lifestyle – together with smoking, obesity and malnutrition – are the four pillars of high risk for many non-communicable diseases. Starting with the landmark studies of Paffenbarger et al. and Blair et al., more than 100 epidemiological studies have examined the association between regular physical activity and a reduction in risk to health with mortality as a hard endpoint. There is a continuum from inactivity to regular physical activity: Epidemiological data show an increase in premature cardiovascular mortality with too much time spent sitting, a sedentary lifestyle or physical inactivity (with high risk) to moderate or vigorous activity (with low or reduced risk) of premature mortality. This continuum can be characterized as an exercise deficiency syndrome (Figure 1). Regular exercise improves heart and lung function, reduces metabolic dysfunction, prevents certain types of cancer, reduces depression and increases cognitive function. There is also an increase in the quality of life and longevity. Most epidemiological studies on adequate physical activity show extensive cardiovascular benefits. This is also shown in the paper in this issue by Cheng et al. The authors report a meta-analysis of epidemiological studies relating to physical activity and cardiovascular mortality. The analysis consists of studies performed from 2004 to 2017. This represents a current update of recent studies on physical activity. The investigators addressed the dose–response relationship between the amount or intensity of activity and the corresponding decrease in cardiovascular mortality risk. Unlike many other studies and meta-analyses, Cheng et al. report a linear relationship between the reduction in risk of cardiovascular mortality and the level of activity. This finding is in sharp contrast with many previous studies with a typical non-linear relationship of dose–response and flattening of the curve with increasing intensity of activity, which is classified as vigorous. There are many explanations for this discrepancy. First, the authors compared moderate to low and vigorous intensity, but did not include the ‘‘zero’’ activity or phases of chronic inactivity as in most other studies. This explains the different and non-linear course of the dose–response relationship. The change from physical inactivity to low or moderate activity is the most important relative step and reveals the greatest and most significant effect regarding risk reduction. Thus, with this relationship, the dose– response curve will usually be non-linear. Second, the inclusion in the study of patients with cardiac diseases who were unable to exercise vigorously may be the reason for the small amount of data on vigorous activity.