Influence of number of drugs on olfaction in the elderly

The etiology of age-related olfactory loss is still unclear, but it has been claimed that polypharmacotherapy may contribute to olfactory dysfunction, particularly in the elderly, who are more likely to need multiple drugs. The present pilot study investigated the relationship between smell and the number and type of drugs taken in a group of elderly.

50 elderly volunteers (over 64 years old) who were healthy from the sinonasal standpoint (SNOT-22 under 1) and had no cognitive impairments [Mini Mental State Examination (MMSE over 18) were administered the Screening 12 test and tested on their n-butanol olfactory threshold. Their olfactory performance was then connected with the number and type of drugs participants used.

The mean age of the included volunteers was 74 plus/minus 7 years. No association emerged between odor identification and number of drugs taken. The number of drugs taken correlated directly with a worse olfactory threshold and with a worse MMSE score, meaning a worse cognitive status. Odor identification significantly worsened with age. Comparing those volunteers taking only one drug known to not influence olfaction with another sub-group of volunteers taking five or more drugs, it was evident that subjects taking only one drug scored significantly better in olfactory threshold test and MMSE, and marginally better in olfactory identification test. For what concerns the difference between male and female volunteers, no difference in olfactory test result was shown, both for threshold and identification. Univariate analysis showed a direct correlation between the consumption of calcium channel blockers, beta-blockers, acetylsalicylic acid and olfactory threshold, meaning a worse sense of smell. Acetylsalicylic acid also correlated inversely with odor identification, meaning again a worse sense of smell, and so did potassium-sparing diuretics. Multivariate analysis showed that MMSE scores correlated with a better sense of smell, that is a lower olfactory threshold, and that beta-blockers and acetylsalicylic acid negatively affected olfactory threshold, meaning a worse sense of smell. Acetylsalicylic acid also correlated inversely with odor identification, meaning again a worse sense of smell.

The number of drugs taken demonstrated to be significantly correlated with a worse olfactory threshold and worse MMSE. Larger studies on elderly volunteers are needed to confirm these preliminary findings.