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Q Are haemoglobin (Hb) concentrations associated with mortality risk in older, community dwelling women with disabilities?
Clinical impact ratings GP/FP/Primary care ★★★★★★☆Haematology ★★★★☆☆☆ Geriatrics ★★★★★☆☆
METHODS
Design:
cohort study (Women’s Health and Aging Study I).
Setting:
Baltimore, Maryland, USA.
Patients:
686 women ⩾65 years of age (mean age 78 y, 72% white), who had a Mini-Mental State Examination score ⩾18 and self reported difficulty performing activities in ⩾2 physical function domains.
Risk factors:
Hb concentrations.
Outcomes:
all cause mortality after a maximum of 6 years of follow up (median 5 y).
MAIN RESULTS
Cumulative all cause mortality was 31%. A non-linear relation existed between Hb and mortality, with highest mortality risk at extreme Hb concentrations and lowest risk in intermediate Hb concentrations. Mildly low Hb concentrations of 110 and 115 g/l were associated with greater mortality risk than an Hb concentration of 120 g/l, even after controlling for major chronic disease burden indicators, whereas mid-normal Hb concentrations of 130 g/l and 140 g/l were associated with lower mortality risk (table). The threshold above which the decline in mortality risk with increasing Hb concentration was no longer statistically significant was 139 g/l.
Association between haemoglobin concentrations and all cause mortality in older, community dwelling women with disabilities*
CONCLUSIONS
In community dwelling older women with disabilities, a haemoglobin (Hb) concentration of 140 g/l was associated with a lower risk of all cause mortality than concentrations of 110 g/l and 120 g/l after adjustment for chronic disease burden. Mortality risk decreased with increasing Hb concentrations up to a threshold of 139 g/l.
Abstract and commentary also appear in ACP Journal Club.
Commentary
A debated clinical question is whether mild anaemia is associated with any health risks, and if so, at what Hb concentration should we make diagnostic or therapeutic decisions? Chaves et al showed that mild anaemia (Hb 115 g/l) was associated with increased mortality in women with disabilities, a finding that is consistent with other studies of elderly populations.1,2 Deriving definitions about normal values (and related thresholds for interventions) based on such data is an improvement over the traditional statistical method that uses data from “normal” persons.
It is unclear whether mild anaemia is a marker for subclinical disease or simply ageing. Chaves et al tried to isolate the independent effect of Hb concentrations on mortality by adjusting for comorbid conditions. They acknowledge that the potential for residual confounding exists.
Izaks et al1 suggest that anaemia is a marker of disease. In a prospective cohort study of persons ⩾85 years of age, they found that neoplasms and infections were more frequent causes of death in those with anaemia than in those with normal Hb concentrations.
Is it worth the effort to search for causes of anaemia in this population? Guralnik et al3 report that about one third of patients ⩾65 years of age with anaemia have nutritional deficiencies (primarily iron deficiency), one third have anaemia secondary to chronic disease, and one third have unexplained anaemia. These data suggest that a treatable cause of anaemia can be identified for most patients.
Further studies are needed to show whether treating elderly patients with mild anaemia has benefits for mortality and for other outcomes, such as functional and cognitive status. Limited testing targeted at identifying treatable causes may be an appropriate strategy. However, 10% of elderly people have anaemia3 with low associated mortality (as shown by Chaves et al). The cost effectiveness of such a strategy needs to be assessed.
Footnotes
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For correspondence: Dr P H M Chaves, Johns Hopkins Center on Aging and Health, Baltimore, MD, USA. pchavesjhsph.edu
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Source of funding: National Institute of Aging.