Plasma and erythrocyte thiamin concentrations in geriatric outpatients

The objective of this study was a) to determine the plasma and red cell thiamin levels in geriatric outpatients and b) to evaluate, using the rat model, the sensitivity of plasma thiamin concentration as an indicator of nutritional status for this vitamin.

Thirty geriatric outpatients were evaluated for their plasma and erythrocyte thiamin levels.

Plasma and red cell thiamin levels were determined by a microbiologic assay using kloeckera apiculata. Sprague-Dawley rats were fed a thiamin deficient diet. Blood samples were obtained on specified days and the plasma and erythrocyte thiamin levels determined.

Forty-three percent of the subjects studied had plasma thiamin levels below 2 SD of the mean of the younger-age group (20-60 yr) while 57% had a plasma thiamin below 10 ng/ml (the lower reference range of the younger age group). Twenty-seven percent were found to have red cell thiamin levels below 2 SD of the mean of the younger-age group, while 33% had red cell thiamin levels below 138 ng/ml (the lower reference range of the younger-age group). The rat study indicated that plasma thiamin concentration is a sensitive indicator of the nutritional status for this vitamin.

About 50% of geriatric outpatients in this study had low plasma thiamin levels. The long-term effect of a low plasma thiamin level on cognitive functions remains to be investigated.