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

•Both diet and physical activity are important cornerstones for cardiovascular disease (CVD) prevention. Despite their inherent connections, they are rarely considered jointly in epidemiological studies.•Our study based on 85,545 Australian adults aged 45–74 years is among the first to examine the interactive and joint associations of diet and physical activity with CVD outcomes.•Neither diet nor moderate-to-vigorous intensity physical activity (MVPA) was significantly associated with CVD hospitalization. However, having >20% of total MVPA from vigorous-intensity physical activity (VPA) was associated with slightly lower risk of CVD hospitalization. Total MVPA of ≥300 min/week was associated with lower risk of CVD mortality.•Both a high-quality diet and ≥10 min/week of MVPA were associated with a lower risk of all-cause mortality. Accounting for total MVPA, any non-zero level of VPA was associated with lower risk of all-cause mortality.•The multiplicative interaction between diet and physical activity was non-significant for all outcomes. For all outcomes, the lowest risk combinations involved a high-quality diet and the highest MVPA categories. 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 2 behaviors are rarely considered jointly, particularly within the context of CVD prevention. We examined the independent, interactive, and joint associations of diet and physical activity with CVD hospitalization, CVD mortality, and all-cause mortality. CVD-free Australian participants aged 45–74 years (n = 85,545) reported physical activity, diet, sociodemographic, and lifestyle characteristics at baseline (2006–2009) and follow-up (2012–2015), and data were linked to hospitalization and death registries (03/31/2019 for CVD hospitalization and all-cause mortality and 12/08/2017 for CVD mortality). Diet quality was categorized as low, medium, and high based on meeting dietary recommendations. Physical activity was operationalized as (a) total moderate-to-vigorous physical activity (MVPA) as per guidelines, and (b) 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. During a median of 10.7 years of follow-up, 6576 participants were admitted to the hospital for CVD and 6581 died from all cau