Serum cobalamin, homocysteine, and methylmalonic acid concentrations in a multiethnic elderly population: ethnic and sex differences in cobalamin and metabolite abnormalities.

BACKGROUND

Low cobalamin concentrations and mild hyperhomocysteinemia are common in the elderly but ethnic differences have not been defined.

OBJECTIVE

Our objective was to determine the demographic characteristics of cobalamin deficiency in the elderly and its role in their hyperhomocysteinemia.

DESIGN

We measured serum cobalamin, total homocysteine (Hcys), and methylmalonic acid (MMA) concentrations in 725 subjects >60 y old, and folate concentrations in 520 subjects.

RESULTS

After exclusion of subjects taking cobalamin supplements or with renal insufficiency, high prevalences of low cobalamin (11.8%), high MMA (16.6%), and high Hcys (26.1%) concentrations were seen. Most cobalamin concentrations <140 pmol/L appeared to reflect deficiency because 78. 3% of them were accompanied by abnormal metabolites. Subjects with cobalamin concentrations of 140-258 pmol/L had significantly fewer metabolic abnormalities. A low cobalamin concentration and renal insufficiency were the strongest predictors of abnormal Hcys concentrations. Elderly men had higher Hcys concentrations than did women (P = 0.0001). Whites and Latin Americans had lower cobalamin concentrations than did blacks and Asian Americans (P < 0.005). Whites also had higher Hcys concentrations than all the other groups (P < 0.05). When included in the analysis, renal insufficiency in subjects was associated with 23.8% of all high Hcys and 25.5% of all high MMA concentrations; most with renal insufficiency were Asian American and black men.

CONCLUSIONS

Mild cobalamin deficiency is most common in elderly white men and least common in black and Asian American women. Hyperhomocysteinemia, which is most strongly associated with low cobalamin concentrations, is also most common in elderly whites, whereas that associated with renal insufficiency is more common in blacks and Asian Americans. Ethnic differences in cobalamin deficiency and the Hcys patterns associated with it or with renal insufficiency warrant consideration in supplementation strategies. Extending suspicion of deficiency to persons with cobalamin concentrations of 140-258 pmol/L appears to provide more disadvantages than advantages.