Serum cobalamin, homocysteine, and methylmalonic acid concentrations in a multiethnic elderly population: ethnic and sex differences in cobalamin andmetabolite 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 o f cobalamin deficiency in the elderly and its role in their hyperhomocystei nemia. Design: We measured serum cobalamin, total homocysteine (Hcys), and methylm alonic acid (MMA) concentrations in 725 subjects >60 y old, and folate conc entrations in 520 subjects. Results: After exclusion of subjects taking cobalamin supplements or with r enal insufficiency? high prevalences of low cobalamin (11.8%), high MMA (16 .6%), and high Hcys (26.1%) concentrations were seen. Most cobalamin concen trations <140 pmol/L appeared to reflect deficiency because 78.3% of them w ere accompanied by abnormal metabolites. Subjects with cobalamin concentrat ions of 140-258 pmol/L had significantly fewer metabolic abnormalities. A l ow cobalamin concentration and renal insufficiency were the strongest predi ctors of abnormal Hcys concentrations. Elderly men had higher Hcys concentr ations than did women (P = 0.0001). Whites and Latin Americans had lower co balamin concentrations than did blacks and Asian Americans (P < 0.005). Whi tes also had higher Hcys concentrations than all the other groups (P < 0.05 ), When included in the analysis, renal insufficiency in subjects was assoc iated 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. w hich is most strongly associated with low cobalamin concentrations, is also most common in elderly whites, whereas that associated with renal insuffic iency is more common in blacks and Asian Americans. Ethnic differences in c obalamin deficiency and the Hcys patterns associated with it or with renal insufficiency warrant consideration in supplementation strategies. Extendin g suspicion of deficiency to persons with cobalamin concentrations of 140-2 58 pmol/L appears to provide more disadvantages than advantages.