Changes in dietary diversity and subsequent all-cause and cause-specific mortality among Japanese adults: The Japan Collaborative Cohort Study.

Background: Poor dietary habits are a significant changeable factor contributing to negative health effects; however, the connection between variations in dietary diversity over time and mortality remains uncertain. This study aimed to evaluate the association between longitudinal changes in the dietary diversity score (DDS) and mortality in Japanese adults.

Methods: This prospective study included 20,863 adults (13,144 women, 7,719 men) aged 40-79 years from the Japan Collaborative Cohort Study. The DDS was evaluated twice, once at baseline and again 5 years later, using a validated food frequency questionnaire that assessed 33 food items. Participants were classified into four groups based on mean DDS: baseline low DDS/5 years later low DDS (n=7,866; Low/Low group), baseline low DDS/5 years later high DDS (n=2,951; Low/High group), baseline high DDS/5 years later low DDS (n=3,000; High/Low group), and baseline high DDS/5 years later high DDS (n=7,046; High/High group). Survival data were collected until 2009, and hazard ratios (HRs) for mortality were calculated using a Cox proportional hazards model.

Results: During a median follow-up of 14.8 years (256,277 person-years), 2,995 deaths were documented. After adjusting for confounders, participants in the High/High group had a lower HR for mortality from all causes (HR:0.82; 95% confidence interval [CI]:0.74-0.91) and cardiovascular disease (HR:0.81; 95% CI:0.67-0.98) than those in the Low/Low group. Similar associations were observed with dairy, soy, and vegetables/fruits, but they were validated exclusively in women.

Conclusions: This study showed that maintaining a higher DDS may be associated with lower mortality in women.