Association between hemoglobin levels and mild cognitive impairment in generally healthy European community-dwelling older adults: a 3-year prospective analysis of the DO-HEALTH trial

Abstract

Background: Although numerous cross-sectional studies have examined the relationship between anemia and cognitive impairment or dementia in older adults, data from larger longitudinal studies, especially in generally healthy older adults, are limited.

Objectives: To investigate the associations between baseline hemoglobin levels, anemia, and mild cognitive impairment (MCI) over 3 y in generally healthy older adults.

Methods: This is an observational analysis of the 3-y DO-HEALTH trial, a double-blind, randomized controlled trial including 2157 European community-dwelling adults age 70+. Cognition was assessed at baseline, 12, 24, and 36 mo using the Montreal Cognitive Assessment (MoCA). MCI was defined as a MoCA score <26 at 2 consecutive time points. The exposures were the quintiles of hemoglobin levels and anemia at baseline. Logistic regression models based on generalized estimating equations controlled for age, sex, prior falls, study site, treatment allocation, body mass index, number of comorbidities, smoking status, use of iron supplements, alcohol consumption, renal function, and vitamin B12 levels.

Results: A total of 2150 participants were included in the analyses (mean age of 74.9 y; 61.7% females). Compared with the lowest quintile, participants in all higher quintiles had a significantly lower odds of MCI: 2nd = 34% lower odds of MCI [odds ratio (OR) = 0.66; 95% confidence interval (CI): 0.47, 0.93; P = 0.02], 3rd = 39% (OR = 0.61; 95% CI: 0.43, 0.86; P = 0.005), 4th = 44% (OR = 0.56; 95% CI: 0.39, 0.82; P = 0.003), and 5th = 36% (OR = 0.64; 95% CI: 0.43, 0.97; P = 0.03). For anemia, there was no association with the odds of MCI over time.

Conclusions: Baseline hemoglobin levels >130 g/L were associated with reduced odds of MCI over 3 y. Although this study does not establish causality, it suggests further investigations in monitoring and managing hemoglobin levels, even in generally healthy older adults. This trial was registered at clinicaltrials.gov as NCT01745263.

Keywords: DO-HEALTH; anemia; hemoglobin; mild cognitive impairment; older adults.