Cobalamin levels are not reduced in Alzheimer's disease: results from a population-based study

To determine whether there is a relationship between serum cobalamin levels, normal aging, and Alzheimer's Disease (AD).

Cross-sectional survey.

A district (Kungsholmen) in Stockholm, Sweden.

Population-based cohort of 545 subjects aged more than 74 years. The sample was selected on the basis of evidence of cognitive impairment from all inhabitants in an area of Stockholm (2368 individuals), both living at home or in institutions.

Serum cobalamin levels and diagnostic evaluation for a diagnosis of dementia and type of dementia.

The serum cobalamin levels in non-demented individuals decreased 5.5 pmol/L with an increase of 1 year of age (regression coefficient = -5.53; P < 0.0001). However, the regression coefficient was 0.21 (P = 0.91) in demented people and 2.57 (P = 0.32) in AD subjects. There was no difference between serum cobalamin levels in demented, AD, and non-demented subjects, except for the oldest ages where demented people and AD sufferers showed higher values. AD patients still living in their own homes had significantly lower cobalamin concentrations compared with institutionalized AD sufferers. The prevalence rate of cobalamin deficiency was 15.5% (95% CI = 11.5-19.5) in normal aging and 18.1% (95% CI = 10.3-25.9) in AD.

These data suggest that serum cobalamin levels decrease in normal aging, but not in dementia or AD. A lower cobalamin concentration observed in AD sufferers still living in their own homes compared with institutionalized persons with AD seemed to be related to but not fully explained by eating habits. Patients with AD living in their own homes are at risk of developing cobalamin deficiency, and monitoring of serum cobalamin concentrations might be useful in this group.