Abstract MP38: Association of Changes in Plant-Based Diet Indices with Total and Cause-Specific Mortality

Introduction: Plant-based diets have been associated with health benefits, including lower risk of type 2 diabetes (T2D) and coronary heart disease (CHD). However, the association between plant-based diets and mortality remains unclear as previous studies did not take into account the quality of plant-based foods. To overcome this limitation, we recently developed three plant-based diet indices—an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI, emphasizing processed carbohydrates and fats)—and reported that hPDI and uPDI were differentially associated with T2D and CHD. In this study, we investigate associations between long-term changes in plant-based diet indices and subsequent total and cause-specific mortality in the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). Hypothesis: We hypothesized that improved plant-based diet quality is associated with lower total and cardiovascular disease (CVD) mortality. Method: We included 47,983 women, aged 63±7y (mean±SD) in the NHS and 25,737 men, aged 63±9y in the HPFS who had no history of CVD or cancer on or before 1998 (baseline). We used multivariable Cox proportional-hazards regression to assess the association between 12-y pre-baseline changes (1986-1998) in three plant-based diet indices and subsequent total and cause-specific mortality (1998-2014). We adjusted for age, race, initial corresponding plant-based diet index score, BMI, family history of diabetes, myocardial infarction, or cancer, history of hypertension, hypercholesterolemia, or T2D, medications, postmenopausal status and postmenopausal hormone use in women, initial and 12-y pre-baseline changes in weight and other lifestyle-related factors. Results: Compared with those participants whose diets remained relatively stable during the pre-baseline 12-year period, among participants with the greatest increase in plant-based diet indices, the pooled hazard ratio (95% confidence interval [CI]) for total mortality was 0.92 (95% CI, 0.87 to 0.97) for PDI, 0.90 (95% CI, 0.86 to 0.95) for hPDI, and 1.11 (95% CI, 1.05 to 1.16) for uPDI. For CVD-specific mortality, a 10-point increase in hPDI was associated with a 10% lower risk (95% CI, 5 to 15), while a 10-point increase in uPDI was associated with a 6% higher risk (95% CI, 0 to 12). We found no evidence for changes in plant-based diet indices and subsequent risk of cancer mortality. Conclusions: Improved plant-based diet quality over a 12-year period was associated with a lower risk of total and CVD mortality, whereas increased consumption of an unhealthful plant-based diet was associated with a higher risk of total and CVD mortality.