Sustained adherence to a Mediterranean diet and physical activity on all-cause mortality in the Melbourne Collaborative Cohort Study: application of the g-formula
26 December 2019
This study aimed to calculate the proportion of deaths that could be prevented over a 14-year period through making long-term changes in lifestyle (diet and physical activity). Over 22,000 people were included in the study and filled out questionnaires about their lifestyle at three different time points. The authors used statistical methods that take into account how lifestyle measurements change over time and estimated the relative impact that different lifestyle factors have on death. The study suggests that being more physically active in middle age is more likely to reduce mortality than maintaining a Mediterranean-style diet.
Share this page
Elizabeth J. Williamson, Julia Polak, Julie A. Simpson, Graham G. Giles, Dallas R. English, Allison Hodge, Lyle Gurrin & Andrew B. Forbes
BMC Public Health volume 19, Article number: 1733 (2019)
Background Adherence to a traditional Mediterranean diet has been associated with lower mortality and cardiovascular disease risk. The relative importance of diet compared to other lifestyle factors and effects of dietary patterns over time remains unknown.
Methods We used the parametric G-formula to account for time-dependent confounding, in order to assess the relative importance of diet compared to other lifestyle factors and effects of dietary patterns over time. We included healthy Melbourne Collaborative Cohort Study participants attending a visit during 1995–1999. Questionnaires assessed diet and physical activity at each of three study waves. Deaths were identified by linkage to national registries. We estimated mortality risk over approximately 14 years (1995–2011).
Results Of 22,213 participants, 2163 (9.7%) died during 13.6 years median follow-up. Sustained high physical activity and adherence to a Mediterranean-style diet resulted in an estimated reduction in all-cause mortality of 1.82 per 100 people (95% confidence interval (CI): 0.03, 3.6). The population attributable fraction was 13% (95% CI: 4, 23%) for sustained high physical activity, 7% (95% CI: − 3, 17%) for sustained adherence to a Mediterranean-style diet and 18% (95% CI: 0, 36%) for their combination.
Conclusions A small reduction in mortality may be achieved by sustained elevated physical activity levels in healthy middle-aged adults, but there may be comparatively little gain from increasing adherence to a Mediterranean-style diet.