Hemoglobin concentration and cognitive impairment in the renal REasons for Geographic And Racial Differences in Stroke (REGARDS) Study.
BACKGROUND
There is growing interest in determining the degree of anemia, which is clinically significant. The goal of this study was to determine the association between hemoglobin concentration and cognitive impairment in a large sample of U.S. adults.


METHODS
We used cross-sectional data from 19,701 adults participating in the REasons for Geographic And Racial Differences in Stroke study. Cognitive impairment was defined as a score of 4 or less on the six-item screener. Hemoglobin was analyzed in 1 g/dL increments relative to the World Health Organization (WHO) threshold (<13 g/dL for men and <12 g/dL for women).


RESULTS
The mean hemoglobin concentration was 13.7 ± 1.5 g/dL. The prevalence of cognitive impairment increased from 4.3% among individuals with a hemoglobin >3 g/dL above the WHO threshold to 16.8% for those with a hemoglobin ≥2 g/dL below the WHO threshold. After adjustment for demographics, chronic health conditions, health status, and inflammation, the association between reduced hemoglobin and cognitive impairment was attenuated and no longer significant, including among those with hemoglobin ≥2 g/dL below the WHO threshold (odds ratio 1.39, 95% confidence interval = 0.94-2.04). A test for linear trend was of borderline significance (p value = .06). For 94% of the sample within 2 g/dL of the WHO threshold, there was no relationship between hemoglobin concentration and the odds of cognitive impairment. The associations did not differ by sex and race.


CONCLUSIONS
Within a large sample of community-dwelling adults, there was no significant association between hemoglobin concentration and cognitive impairment after multivariable adjustment.
Kurella Tamura
Manjula
M
Division of Nephrology, Stanford University School of Medicine, 780 Welch Road, Palo Alto, CA 94304, USA. mktamura@stanford.edu
Wadley
Virginia G
VG
Newsome
Britt B
BB
Zakai
Neil A
NA
McClure
Leslie A
LA
Howard
George
G
Warnock
David G
DG
McClellan
William
W
D000368:Aged; D000740:Anemia / Q000150:complications / Q000453:epidemiology; D044383:Black People / Q000706:statistics & numerical data*; D003072:Cognition Disorders / Q000097:blood* / Q000150:complications / Q000453:epidemiology* / Q000503:physiopathology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003710:Demography; D005260:Female; D005919:Glomerular Filtration Rate; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D009994:Osmolar Concentration; D015995:Prevalence; D051437:Renal Insufficiency / Q000150:complications*; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data*; D001741:Black or African American
D006454:Hemoglobins