Lower Hemoglobin Levels Correlate with Raised Mortality in Older People

Anemia is a lowered level of red blood cells and hemoglobin, leading to a diminished supply of oxygen to tissues and thus degraded function throughout the body. The anemia of aging, like all issues in later life, is a gradual onset, a sliding scale of dysfunction with an arbitrary line in the sand as how low hemoglobin must fall for it to be formally considered a medical condition. There are consequences prior to that point of course, as the study data here illustrates. The relationship between lower hemoglobin levels and higher mortality is linear. It is, however, an open question as to how much of this relates to downstream consequences of lower hemoglobin levels and how much is a case of individuals with a greater burden of molecular damage and dysfunction tending to have lower hemoglobin levels.

An increase in life expectancy has emphasized anemia as a public health concern because of the associated healthcare needs and financial burden it incurs. Anemia is common among older adults with the estimated prevalence of 17% among individuals aged ≥65 years. A large cohort study has found that the prevalence of anemia increased with age from 4 to 6% in those aged 65-69 years to 13-14% in those aged ≥85 years. Anemia has been associated with a range of adverse events including falls, cognitive deficits, hospitalization, and mortality among older adults.

Anemia has been defined as hemoglobin (HB) concentrations of less than 12.0 g/dL and 13.0 g/dL in women and men, respectively. Some studies have reported that relatively lower HB concentrations were predictors of increased risk of mortality, which were due to decreased oxygen carrying capacity causing left ventricular hypertrophy and ischemia. More recently, several prospective cohort studies have indicated that a non-linear association exists between HB concentrations and all-cause mortality. Anemia may be prevalent in the general population, particularly in older adults. The effect of HB concentrations is associated with infection, autoimmune disease, and chronic kidney disease. In the current study, we aimed to evaluate the relationship between HB concentrations and all-cause mortality among 1,785 older adults aged ≥65 years form Chinese longevity regions, using community-based cohort data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS).

In total, 999 deaths occurred during a median follow-up of 5.4 years from 2011 to 2017. Analysis found no non-linear association between HB concentrations and all-cause mortality after a full adjustment for covariates among the older adults form longevity regions. The risk for all-cause mortality was significantly higher in the groups with HB concentration of less than 11.0 g/dL (hazard ratio: 1.37) and 11.0-12.0 g/dL (hazard ratio: 1.25); the risk of all-cause mortality was significantly lower in the groups with HB concentration greater than 14.0 g/dL (hazard ratio: 0.76) compared with the reference group (13.0-13.9 g/dL). This HB concentrations were found to be inversely and linearly associated with all-cause mortality.

Link: https://doi.org/10.3389/fpubh.2021.787935

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