Cumulative incidence of vitamin B12 deficiency in patients with Alzheimer disease

Although vitamin B12 is routinely measured in patients with Alzheimer disease (AD) at the time of the initial diagnosis, it is not known if repeat vitamin B12 measurements are indicated to detect new deficiency cases. We aimed to determine the incidence of de-novo vitamin B12 deficiency over a period of 3 years in a cohort of AD patients without a prior diagnosis of vitamin B12 deficiency and with initial vitamin B12 levels greater than 350 ng/L.

Vitamin B12 levels were measured at the time of AD diagnosis and repeated 3 years later in 102 consecutive patients, unless a diagnosis of B12 deficiency was made in the interim.

Vitamin B12 deficiency was diagnosed in 7 patients, corresponding to a cumulative incidence in the cohort studied of 7.6% after 3 years of follow-up. Statistical comparison of initial and repeat vitamin B12 measurements in patients that completed follow-up showed a significant reduction in levels (p=0.003). Among the 79 subjects with follow-up, 17 patients (22%, 95% CI, 13%-32%) had a repeat level less than 350 ng/L. No significant correlates of deficiency incidence were identified.

Our pilot data indicate that vitamin B12 levels decreased in this cohort of AD patients putting a substantial percentage at risk of deficiency and reaching deficiency state in a meaningful number of patients. Repeat screening for B12 deficiency after approximately 2 years of follow-up seems warranted in order to prevent hematological and neurological manifestations that may significantly alter their quality of life.