The Relationship Between Diet Quality and 21-Year Cumulative Health Care Costs Among Australian Women: A Longitudinal Cohort Study.

Background: The relationships between diet quality and health care costs have not been explored beyond 15 years.

Objective: To investigate relationships between both baseline diet quality and change in diet quality over time with cumulative data on health care claims and costs over 21 years among Australian women.

Design: This is a secondary analysis of data from a cohort study, the Australian Longitudinal Study on Women's Health.

Participants/setting: Data for women born between 1946 and 1951 included diet quality data at baseline (2001, n = 8228), change in diet quality (2001-2013, n = 6553), and cumulative administrative health care data (2001-2021).

Main outcomes: Diet quality was assessed using the Australian Recommended Food Score (ARFS) and the Fruit and Vegetable Variety Score. Twenty-one-year cumulative Medicare Benefits Schedule data (number of claims; total charges [$USD]), Australia's universal health care coverage, were reported by baseline ARFS quintile and category of diet quality change ("diet quality worsened" [ARFS decrease ≤ -4 points], "remained stable" [-3 ≤ change in ARFS ≤ 3 points] or "improved" [ARFS increase ≥ 4 points]).

Statistical analysis: Linear regression analyses were conducted and adjusted for socioeconomic, health, and lifestyle factors.

Results: Higher baseline vegetable ARFS were correlated with fewer 21-year cumulative Medicare claims (β = -4.9, 95% CI, -7.3, -2.4) and charges (β = -$214; 95% CI, -$341; -$88). Baseline higher dairy scores were correlated with higher Medicare claims (β = 17.2; 95% CI, 11.1, 23.3) and charges (β = $762; 95% CI, $448, $1076). Compared with women whose diet quality score remained stable, those whose diet quality worsened over time made significantly more claims and higher charges; median (Q1, Q3) 413 (277, 588) claims, $17 868 ($11 037, $27 808) cumulative charges, compared with 387 (259, 559) claims, and $16 953 ($10 033, $26 604) cumulative charges. Change in total ARFS and ARFS subscales were predictors of 21-year cumulative health care claims. For each 1-point increase in ARFS over time, 1.2 fewer health care claims were made (95% CI, 0.3-2.2). Increasing vegetable and dairy ARFS scores were correlated with significantly fewer claims.

Conclusions: Baseline greater variety of vegetables was correlated with fewer 21-year health care claims and costs. Worsening diet quality over time was correlated with greater cumulative health care claims and costs. Consideration of dietary quality and variety in national policy is suggested to potentially reduce national health care claims and costs.