Haemoglobin, anaemia, dementia and cognitive decline in the elderly, a systematic review.
BACKGROUND
Anaemia may increase risk of dementia or cognitive decline. There is also evidence that high haemoglobin levels increase risk of stroke, and consequently possible cognitive impairment. The elderly are more at risk of developing dementia and are also more likely to suffer from anaemia, although there is relatively little longitudinal literature addressing this association.


METHODS
To evaluate the evidence for any relationship between incident cognitive decline or dementia in the elderly and anaemia or haemoglobin level, we conducted a systematic review and meta-analyses of peer reviewed publications. Medline, Embase and PsychInfo were searched for English language publications between 1996 and 2006. Criteria for inclusion were longitudinal studies of subjects aged > or =65, with primary outcomes of incident dementia or cognitive decline. Other designs were excluded.


RESULTS
Three papers were identified and only two were able to be combined into a meta-analysis. The pooled hazard ratio for these two studies was 1.94 (95 percent confidence intervals of 1.32-2.87) showing a significantly increased risk of incident dementia with anaemia. It was not possible to investigate the effect of higher levels of haemoglobin.


CONCLUSIONS
Anaemia is one factor to bear in mind when evaluating risk of incident dementia. However, there are few data available and the studies were methodologically varied so a cautionary note needs to be sounded and our primary recommendation is that further robust research be carried out.
Peters
Ruth
R
Experimental Medicine and Toxicology, Imperial College Faculty of Medicine, Hammersmith campus, Du Cane Road, London, W12 0NN, UK. r.peters@imperial.ac.uk
Burch
Lisa
L
Warner
James
J
Beckett
Nigel
N
Poulter
Ruth
R
Bulpitt
Christopher
C
D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000740:Anemia / Q000150:complications* / Q000175:diagnosis; D003072:Cognition Disorders / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D016001:Confidence Intervals; D003704:Dementia / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D015577:Geriatric Assessment; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D011336:Probability; D011379:Prognosis; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution
D006454:Hemoglobins