Epidemiologists here note that there is no interaction between the correlations of physical activity and diet with mortality risk, at least in the measures used for this study. Additionally the researchers quantify the size of the survival benefit produced by increased exercise or improved diet. While analysis of human data can only demonstrate correlations, animal studies have comprehensively demonstrated causation in these matters. It is quite reasonable at this point to assume causation when observing a correlation between these lifestyle choices and mortality risk.
A prospective cohort study was performed on 9,349 adults aged 40 to 79 years from the population-based European Prospective Investigation into Cancer in Norfolk Study, with repeated measurements of physical activity (PA) and diet (from 1993 till 2004) and subsequent follow-up till 2022 (median follow-up 18.8 years). Validated questionnaires were used to derive physical activity energy expenditure (PAEE) as a proxy of total PA and adherence to the Mediterranean diet score (MDS, range 0-15 points) as an indicator of overall diet quality, and their changes over time (∆PAEE and ∆MDS).
Over 149,681 person-years of follow-up, there were 3,534 deaths. In adjusted models, for each 1 standard deviation difference in baseline PAEE (4.64 kJ/kg/day), ∆PAEE (0.65 kJ/kg/day per year), baseline MDS (1.30 points) and ∆MDS (0.32 points per year), hazard ratios (HRs) for all-cause mortality were 0.90, 0.89, 0.95, and 0.93, respectively. Compared with participants with sustained low PAEE (under 5 kJ/kg/day) and low MDS (less than 8.5 points), those with sustained high PAEE and high MDS had lower all-cause mortality (HR 0.78), as did those who improved both PAEE and MDS (HR 0.60). There was no evidence of interaction between PA and diet quality exposures on mortality risk. Population impact estimates suggested that if all participants had maintained high levels of PA and diet quality consistently, cumulative adjusted mortality rate would have been 8.8% lower.
These findings suggest that adopting and maintaining higher levels of PA and diet quality are associated with lower mortality. Significant public health benefits could be realised by enabling active living and healthy eating through adulthood.
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