Spouses of demented patients with low cobalamin levels: a new risk group for cobalamin deficiency.

Low serum cobalamin levels are common in conditions such as dementia and often represent mild deficiency. We surveyed serum cobalamin levels prospectively in spouses and blood relatives of demented patients to determine if any familial predisposition exists for the low levels. Cobalamin status in most of the relatives found to have low levels was assessed further by means of blood counts, metabolic tests, neurologic evaluation, absorption studies and response to cobalamin therapy. Serum cobalamin levels in 36 spouses correlated with those of the 36 demented patients related to them (r = 0.46, p = 0.004). A significant association was not seen in 34 blood relatives of 34 demented patients (r = 0.27). Most importantly, 67% of the spouses of demented patients with low serum cobalamin had low values themselves, compared with only 3% of the spouses of patients with normal levels (p = 0.001). Detailed study of 4 of the 5 spouses (and 3 blood relatives) with low cobalamin levels showed no anemia in any case. Nevertheless, 4 of the subjects had metabolic evidence of deficiency and one had electrophysiological abnormalities; all these defects improved with cobalamin therapy. These observations identify a hitherto unsuspected group of people at high risk for cobalamin deficiency and suggest that spouses of demented patients with low cobalamin levels should also have their cobalamin levels measured. The increased frequency of low serum cobalamin levels in spouses of demented patients with low levels represents in most cases a true, mild cobalamin deficiency that responds to treatment.