Milk Intake at Midlife and Cognitive Decline over 20 Years. The Atherosclerosis Risk in Communities (ARIC) Study

Abstract

Background: Faster rates of cognitive decline are likely to result in earlier onset of cognitive impairment and dementia. d-galactose, a derivative of lactose, is used in animal studies to induce neurodegeneration. Milk is the primary source of lactose in the human diet, and its effects on cognitive decline have not been fully evaluated. Objective: Assess the association of milk intake with change in cognitive function over 20 years. Methods: A total of 13,751 participants of the Atherosclerosis Risk in Communities (ARIC) cohort completed a food frequency questionnaire and three neurocognitive evaluations from 1990 through 2013. Two single nucleotide polymorphisms (SNPs) were used to determine lactase persistence (LCT-13910 C/T for Whites and LCT-14010 G/C for Blacks). Mixed-effects models were used to study the association of milk intake with cognitive change. Multiple imputations by chained equations were used to account for attrition. Results: Milk intake greater than 1 glass/day was associated with greater decline in the global z-score over a 20-year period. The difference in decline was 0.10 (95% CI: 0.16, 0.03) z-scores, or an additional 10% decline, relative to the group reporting "almost never" consuming milk. Conclusions: Replication of these results is warranted in diverse populations with greater milk intake and higher variability of lactase persistence genotype.

Keywords: aging; cognitive decline; dementia; lactase persistence; lactose; oxidative stress.

Figure 1

Timeline of the Atherosclerosis Risk in Communities (ARIC) study.

Figure 2

Estimated difference in the 20-year change in cognitive performance by milk intake group relative to those who reported “almost never” consuming milk adjusted for age, gender, race-center, education level, APOE4, BMI, smoking, alcohol intake, diabetes, physical activity, total energy intake and diet quality score. ARIC Study. Abbreviations: DWRT, delayed word recall test; DSST, digit symbol substitution test; WFT, word fluency test. Global z is a summary score, equal to the average of the three domain-specific z-scores.

Figure 3

Estimated difference in the 20-year change in global z-score stratified by race and by LP/LNP genotype among Whites adjusted for age, gender, race-center, education level, APOE4, BMI, smoking, alcohol intake, diabetes, physical activity, total energy intake and diet quality. ARIC Study. Abbreviations: LNP, lactase non-persistence; LP, lactase persistence. “Almost never” used as a referent category.