Relation of hemoglobin to level of cognitive function in older persons

While decreased hemoglobin concentration is common in the elderly, the relationship of the entire range of hemoglobin concentrations with cognitive function is not well understood.

Cross-sectional analyses were conducted utilizing data from community-dwelling, older persons participating in the Rush Memory and Aging Project. Proximate to first available hemoglobin measurement, 21 cognitive tests were administered to measure global cognitive function along with semantic memory, episodic memory, working memory, perceptual speed and visuospatial abilities.

For 793 participants without clinical dementia, stroke or Parkinson's disease, the mean age was 81.0 years (SD = 7.2); 595 (75%) were women, and 94% were white. The mean hemoglobin concentration was 13.3 g/dl (SD = 1.3). 17% of the cohort had anemia. Using linear regression models adjusted for age, education, gender, body mass index, mean corpuscular volume and glomerular filtration rate, both low and high hemoglobin levels were associated with lower global cognitive function (parameter estimate = -0.015, SE = 0.007, p = 0.019). Low and high hemoglobin levels were associated with worse performance on semantic memory (parameter estimate = -0.201, SE = 0.008, p = 0.010) and perceptual speed (parameter estimate = -0.030, SE = 0.010, p = 0.004), but not the other specific cognitive functions.

Low and high hemoglobin concentrations in older persons are associated with a lower level of cognitive function in old age, particularly in semantic memory and perceptual speed.