The association of diet quality and physical activity with cardiovascular disease and mortality in 85,545 older Australians: A longitudinal study

Background A quality diet and an active lifestyle are both important cornerstones of cardiovascular disease (CVD) prevention. However, despite their interlinked effects on metabolic health, the two behaviours are rarely jointly considered, particularly within the context of CVD prevention. We examined the independent, interactive and joint associations of diet and physical activity with CVD hospitalisation, CVD mortality and all-cause mortality. Methods CVD-free Australian participants aged 45-74 years reported physical activity, diet and sociodemographic and lifestyle characteristics at baseline (2006-09) and follow-up (2012-15), and data were linked to hospitalisation and death registries (31/03/2019 for CVD hospitalisation and all-cause mortality and 08/12/2017 for CVD mortality). Diet quality was categorised as low, medium and high based on meeting dietary recommendations. Physical activity was operationalised as 1) total moderate-to-vigorous physical activity (MVPA) as per guidelines and 2) the composition of MVPA as the ratio of vigorous-intensity physical activity (VPA) to total MVPA. We used a left-truncated cause-specific Cox proportional hazards model using time-varying covariates. Results During a median of 10.7 years of follow-up, 6,581 participants were admitted to the hospital for CVD and 6,586 died from all causes (879 from CVD during 9.3 years). A high-quality diet was associated with a 17% lower risk of all-cause mortality than low-quality, and the highest MVPA category (compared with the lowest) was associated with 44% and 48% lower risks of CVD and all-cause mortality. Multiplicative interactions between diet and physical activity were non-significant. For all outcomes, the lowest risk combinations involved a high-quality diet and the highest MVPA categories. Accounting for total MVPA, some VPA was associated with further risk reduction of CVD hospitalisation and all-cause mortality. Conclusion For CVD prevention and longevity, one should adhere to both a healthy diet and an active lifestyle and incorporate some VPA when possible.