Age-Related 12-Year Changes in Dietary Diversity and Food Intakes among Community-Dwelling Japanese Aged 40 to 79 Years.

OBJECTIVES: This study describes trends in dietary diversity and food intake over 12 years according to age at first participation in the study.

DESIGN: Prospective cohort study.

SETTING: The National Institute for Longevity Sciences - Longitudinal Study of Aging, a community-based study.

PARTICIPANTS: Participants included 922 men and 879 women who participated in the first study-wave (age, 40-79 years) and also participated in at least one study-wave from the second to seventh study-wave. Study-waves were conducted biennially.

MEASUREMENTS: Dietary intake was calculated from 3-day dietary records with photographs. Dietary diversity was determined using the Quantitative Index for Dietary Diversity based on food intake. A mixed-effects model was used to estimate linear changes in dietary diversity and food intake over 12 years according to age at first study-wave.

RESULTS: Mean (standard deviation (SD)) follow-up time and number of study-wave visits were 9.5 (3.7) years and 5.4 (1.8), respectively. Mean (SD, range) dietary diversity score was 0.86 (0.06, 0.52-0.96) in men and 0.88 (0.04, 0.66-0.96) in women, respectively. Fixed effects for interactions of age and time with dietary diversity score were statistically significant (p<0.05). The slope of dietary diversity among men aged 40 to 55 years increased (40-year-old slope = 0.00093/year, p<0.01; 55-year-old slope = 0.00035/year, p=0.04), with a decreasing trend started at 65 years old, although this trend was not significant (65-year-old slope = -0.00003/year, p=0.88; 79-year-old slope = -0.00057/year, p=0.21). The slope of dietary diversity among women aged 40 to 44 years increased (40-year-old slope = 0.00053/year, p=0.02; 44-year-old slope = 0.00038/year, p=0.04), whereas the slope of dietary diversity among women aged 63 to 79 years decreased (63-year-old slope = -0.00033/year, p=0.03; 79-year-old slope = -0.00092/year, p<0.001). Fruit, milk and dairy intake decreased in men around their 60s; milk and dairy intake decreased in women around their 50s; and beans and fruit intake decreased in women from their 70s.

CONCLUSION: Twelve-year longitudinal data showed dietary diversity declined in women in their 60s. In terms of food intake, fruit, milk and dairy intake decreased in both sexes in their 50s and 60s; such declines would lower dietary diversity.