Diet quality indexes and mortality in postmenopausal women: the Iowa Women's Health Study.

BACKGROUND: A priori diet scores such as the Alternative Healthy Eating Index (AHEI) and the food-based a priori diet quality score predict chronic disease risk.

OBJECTIVE: We compared the AHEI and a priori diet quality score relative to mortality.

DESIGN: Postmenopausal women who were free of diabetes, cardiovascular disease (CVD), and cancer in the Iowa Women's Health Study (in 1986, n = 29,634 with a mean 6 SD age of 61.4 6 4.2 y; in 2004, n = 15,076 with a mean 6 SD age of 79.7 6 4.0 y). A food-frequency questionnaire was used. Through 31 December 2008, 10,343 total, 3646 CVD, 3207 cancer, and 2888 inflammatory-related deaths were identified through record linkage. HRs were computed for quartiles of each diet score at baseline and 2004. To compare scores, the residual of each score given the other score was computed by using linear regression.

RESULTS: At baseline, indexes had a correlation of 0.65. For the AHEI, the multivariable-adjusted HRs (95% CIs) for total, CVD, cancer, and inflammatory-related mortality were 0.82 (0.77, 0.87), 0.79 (0.72, 0.88), 0.88 (0.79, 0.98), and 0.76 (0.68, 0.84), respectively. The a priori score had corresponding HRs of 0.80 (0.76, 0.85), 0.79 (0.72, 0.88), 0.86 (0.77, 0.95), and 0.75 (0.67, 0.84), respectively. Each score added information to the other score for total, CVD mortality, and inflammatory-related mortality. In 2004, both scores predicted total, CVD, and inflammatory-related mortality, and the a priori score also predicted cancer mortality. The a priori score added independent information for all outcomes except cancer, whereas the AHEI added information only for total mortality.

CONCLUSION: Two correlated diet quality scores predicted total and disease-specific mortality, but their residuals also predicted complementarily.