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Studies explore the impact of medication use on cognitive functioning among community-dwelling elderly
It is estimated that one person in five over 65 years of age is cognitively impaired to some degree. Medications are among the most common causes of reversible confusional states in elderly people. For example, benzodiazepines—used by 6 to 14 percent of community-dwelling elderly people to manage anxiety and insomnia—have been associated with cognitive impairment. A recent study by Joseph T. Hanlon, Pharm.D., M.S., of the University of Minnesota, and colleagues shows that current benzodiazepine use is associated with decreased memory among community-dwelling elderly people. A second study by the same group reveals different patterns of medication use by community-dwelling elderly people that vary by level of cognitive function. Both studies, which were supported in part by the Agency for Health Care Policy and Research (HS07819), are summarized here.
Hanlon, J.T., Horner, R.D., Schmader, K.E., and others. (1998). "Benzodiazepine use and cognitive function among community-dwelling elderly." Clinical Pharmacology and Therapeutics 64(6), pp. 684-692.
Community-dwelling elderly people who use benzodiazepines have worse memory than those who don't use these medications, found this study. After adjusting for the effects of demographic characteristics, health status, and health behaviors, current benzodiazepine users made more errors on memory tests than nonusers. Those who took benzodiazepines long term or in recommended or higher doses made even more memory errors than short-term or lower dose users. Memory was impaired even though the average current benzodiazepine dose was about 4 mg per day of diazepam equivalence, an initial starting dose recommended for the elderly.
The risk of cognitive impairment should be balanced against the clinical benefit of benzodiazepine use in the elderly. Also, elders should be given prescriptions for smaller total daily doses, conclude the researchers. They prospectively studied 2,765 community-dwelling elderly patients for 3 years. They assessed cognitive function with the Short Portable Mental Status Questionnaire and the Orientation-Memory-Concentration Test.
The researchers found that previous benzodiazepine use was unrelated to memory problems, and current and previous benzodiazepine use was unrelated to other aspects of cognitive functioning as measured with four other tests. Also, those who took benzodiazepines with a short half-life or long half-life had impaired memory. This finding is contrary to a common tenet among geriatricians that benzodiazepines with a short half-life are safer (less likely to result in falls and resulting fractures) and preferred for use among the elderly.
Schmader, K.E., Hanlon, J.T., Fillenbaum, G.G., and others. (1998). "Medication use patterns among demented, cognitively impaired and cognitively intact community-dwelling elderly people." Age and Ageing 27, pp. 493-501.
The more cognitively impaired a community-dwelling elderly person is, the less apt that individual is to use over-the-counter (OTC), cardiovascular, and analgesic medications, as well as prescription medications overall, finds this study. For instance, demented people were significantly less likely than cognitively impaired (but not demented) elders to use any OTC medications (odds ratio [OR] of 0.65; 1 is equal odds), cardiovascular medications (OR of .70), and analgesics (OR of 0.54).
It is possible that demented patients may underreport pain or express pain in atypical ways, or that clinicians may undertreat pain in demented patients. Alternatively, demented patients in this study were less apt to have arthritis, a leading indication for analgesic medications. The higher use of analgesics by those who were not demented may represent a protective effect of certain diseases or the medications used to treat them. This explanation is consistent with growing evidence on the protective effects of antiinflammatory medications on the development of Alzheimer's disease and also with a lower than expected prevalence of Alzheimer's disease in patients with rheumatoid arthritis.
In this racially mixed sample of community-dwelling elderly people in North Carolina, the proportion of demented people using medications (87 percent) and the average number of medications per person (3.4) were substantial. As a combined group, those who were demented and cognitively impaired were less likely than the cognitively intact group to use any OTC medications (OR of 0.78), but they took similar numbers of prescription medications. These results were based on medication use in the previous 2 weeks as ascertained during an interview in the patient's home.
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