OBJECTIVE: To explore the associations of low serum levels of vitamin B12 and folate with AD occurrence.
METHODS: A population-based longitudinal study in Sweden, the Kungsholmen Project. A random sample of 370 nondemented persons, aged 75 years and older and not treated with B12 and folate, was followed for 3 years to detect incident AD cases. Two cut-off points were used to define low levels of vitamin B12 (150 and 250 pmol/L) and folate (10 and 12 nmol/L), and all analyses were performed using both definitions. AD and other types of dementia were diagnosed by specialists according to DSM-III-R criteria.
RESULTS: When using B12 150pmol/L and folate 10 nmol/L to define low levels, compared with people with normal levels of both vitamins, subjects with low levels of B12 or folate had twice higher risks of developing AD (relative risk [RR] = 2.1, 95% CI = 1.2 to 3.5). These associations were even stronger in subjects with good baseline cognition (RR = 3.1, 95% CI = 1.1 to 8.4). Similar relative risks of AD were found in subjects with low levels of B12 or folate and among those with both vitamins at low levels. A comparable pattern was detected when low vitamin levels were defined as B12 250 pmol/L and folate 12 nmol/L.
CONCLUSIONS: This study suggests that vitamin B12 and folate may be involved in the development of AD. A clear association was detected only when both vitamins were taken into account, especially among the cognitively intact subjects. No interaction was found between the two vitamins. Monitoring serum B12 and folate concentration in the elderly may be relevant for prevention of AD.