Age-related changes in cobalamin (vitamin B12) handling. Implications for therapy.

Abstract

Cobalamin (vitamin B12) deficiency is more common in the elderly than in younger patients. This is because of the increased prevalence of cobalamin malabsorption in this age group, which is mainly caused by (autoimmune) atrophic body gastritis. Cobalamin supplementation is affordable and nontoxic, and it may prevent irreversible neurological damage if started early. Elderly individuals with cobalamin deficiency may present with neuropsychiatric or metabolic deficiencies, without frank macrocytic anaemia. An investigation of symptoms and/or signs includes the diagnosis of deficiency as well as any underlying cause. Deficiency states can still exist even when serum cobalamin levels are higher than the traditional lower reference limit. Cobalamin-responsive elevations of serum methylmalonic acid (MMA) and homocysteine are helpful laboratory tools for the diagnosis. The health-related reference ranges for homocysteine and MMA appear to vary with age and gender. Atrophic body gastritis is indirectly diagnosed by measuring serum levels of gastrin and pepsinogens, and it may cause dietary cobalamin malabsorption despite a normal traditional Schilling's test. The use of gastroscopy may also be considered to diagnose dysplasia, bacterial overgrowth and intestinal villous atrophy in healthy patients with atrophic body gastritis or concomitant iron or folic acid deficiency. Elderly patients respond to cobalamin treatment as fully as younger patients, with complete haematological recovery and complete or good partial resolution of neurological deficits. Chronic dementia responds poorly but should, nevertheless, be treated if there is a metabolic deficiency (as indicated by elevated homocysteine and/or MMA levels). Patients who are at risk from cobalamin deficiency include those with a gastrointestinal predisposition (e.g. atrophic body gastritis or previous partial gastrectomy), autoimmune disorders [type 1 (insulin-dependent) diabetes mellitus and thyroid disorders], those receiving long term therapy with gastric acid inhibitors or biguanides, and those undergoing nitrous oxide anaesthesia. To date, inadequate cobalamin intake has not proven to be a major risk factor. Intervention trials of cobalamin, folic acid and pyridoxine (vitamin B6) in unselected elderly populations are currently under way.