Cause-specific and all-cause mortalities in vegetarian compared with those in nonvegetarian participants from the Adventist Health Study-2 cohort.

Background: There have been mixed results reported internationally when associating vegetarian dietary patterns with all-cause and cause-specific mortalities.

Objectives: This study aimed to extend our previous results by evaluating, with a larger number of deaths (N = 12,515), cause-specific mortalities comparing different vegetarian types with nonvegetarians.

Methods: This prospective study used data from the Adventist Health Study-2 cohort. Mortality was ascertained between study baseline, 2002-2007, and follow-up through 2015. Dietary data were collected at baseline using a validated quantitative food frequency questionnaire and then categorized into 5 dietary patterns: nonvegetarian, semivegetarian, pescovegetarian, lacto-ovovegetarian, and vegan. Main outcomes and measures include all-cause and cause-specific mortalities using Cox proportional hazards regression models and competing risk methods.

Results: The analytic sample included 88,400 participants who provided 971,424 person-years of follow-up. We report results pairwise as estimated at ages 65 and 85 y owing to age dependence of many hazard ratios (HRs). Compared with nonvegetarians, vegetarians had lower risks of mortality, overall (HR: 0.89; 95% confidence interval [CI]: 0.83, 0.95; HR: 0.98; 95% CI: 0.91, 1.04), from renal failure (HR: 0.52; 95% CI: 0.38, 0.70; HR: 0.65; 95% CI: 0.55, 0.76), infectious disease (HR: 0.57; 95% CI: 0.40, 0.82; HR: 0.90; 95% CI: 0.70, 1.17), diabetes (HR: 0.51; 95% CI: 0.33, 0.78; HR: 0.69; 95% CI: 0.53, 0.88), select cardiac (HR: 0.75; 95% CI: 0.65, 0.87; HR: 0.89; 95% CI: 0.83, 0.95), and ischemic heart disease causes (HR: 0.73; 95% CI: 0.59, 0.90; HR: 0.84; 95% CI: 0.75,0.94). Vegans, lacto-ovovegetarians, and pescovegetarians were also observed to have lower risks of total mortality and several similar cause-specific mortalities. However, higher cause-specified neurologic mortalities were observed among older vegetarians (estimated at age 85 y), specifically stroke (HR: 1.17; 95% CI: 1.02, 1.33), dementia (HR: 1.13; 95% CI: 1.00, 1.27), and Parkinson's disease (HR: 1.37; 95% CI: 0.98, 1.91). Results in Black subjects for vegetarian/nonvegetarian comparisons largely followed the same trends, but HRs were less precise owing to smaller numbers.

Conclusions: Vegetarian diets are associated with lower risk for all-cause and many cause-specific mortalities, especially among males and in younger subjects. However, higher risks are observed among older vegetarians for stroke and dementia. These results need further support and investigation.