Use of medicines by older people in a large British national survey, and their relation to vitamin status indices

Objective: To describe the extent of use of medicines by older people living in Britain, and to explore relationships with vitamin status indices. Design: The National Diet and Nutrition Survey of people aged 65 years and over collected data from a British sample during 1994-95. The present study has made novel use of it, to relate medicine use with biochemical indices of vitamin status. Setting: Eighty postcode areas, selected randomly from mainland Britain. Subjects: 1506 people, 65 years and over gave information about use of medication, and a 4-day weighed food record. Three-quarters gave blood for status indices. Results: 78% of those living in the community and 93% of those in institutions were using medication. Certain vitamin status indices: plasma retinol, erythrocyte folate and riboflavin, paradoxically suggested better status in users than in non-users of antihypertensive, gastrointestinal, central nervous system, corticosteroid or diabetic drugs. There was evidence of a link with renal insufficiency, especially for plasma retinol, but neither this nor increased nutrient intake, acute phase effects or haemoconcentration could explain the paradoxical associations. Conclusions: Caution is needed in interpreting certain vitamin status indices, especially in older people who are extensively using medicines. New vitamin indices are needed, to avoid confounding interferences.