Type 2 diabetes mellitus (T2DM) is a risk factor for cognitive dysfunction and dementia in the elderly. T2DM has been thought to be associated with vascular diseases, eventually leading to vascular dementia, but recent studies have established that T2DM is also associated with Alzheimer’s disease (AD). With the increase in the number of elderly individuals with T2DM, the number of diabetic patients with cognitive dysfunction has been increasing. T2DM may accelerate AD-associated pathologies through insulin resistance. Vascular pathologies may also be associated with cognitive dysfunction and dementia in T2DM subjects. Several other mechanisms also seem to be involved in T2DM-related cognitive dysfunction. More investigations to clarify the association of T2DM with cognitive impairment are warranted. These investigations may help to increase our understanding of AD and open a new door to the development of therapeutics. Recent pharmaceutical advancement in T2DM treatment has resulted in the availability of a wide range of antidiabetics. Some evidence has suggested that antidiabetic therapies help to prevent cognitive dysfunction. At present, however, the optimal level of blood glucose control and the best combination of medications to achieve it in terms of cognitive preservation have not been established. More investigation is warranted. Cognitive dysfunction is an emerging new complication of T2DM that requires further study.

Aim: Polypharmacy, which is often observed in elderly patients, has been associated with several unfavorable outcomes, including an increased risk of potentially inappropriate medications, medication non‐adherence, drug duplication, drug–drug interactions, higher healthcare costs and adverse drug reactions. A significant association between polypharmacy and adverse outcomes among older people living in the community has also been confirmed. A reduction in the number of medications should thus be pursued for many older individuals. Nevertheless, the factors associated with polypharmacy in elderly home‐care patients have not been reported. Here, we investigated those factors in elderly home‐care patients in Japan.Methods: We used the data of the participants in the Observational Study of Nagoya Elderly with Home Medical investigation. Polypharmacy was defined as the current use of six or more different medications. We carried out univariate and multivariate logistic regression analyses to assess the associations between polypharmacy and each of several factors.Results: A total of 153 home‐care patients were registered. The mean number of medications used per patient was 5.9, and 51.5% of the patients belonged to the polypharmacy group. The multivariate model showed that the patients’ scores on the Charlson Comorbidity Index and the Mini‐Nutrition Assessment Short Form were inversely associated with polypharmacy, and potentially inappropriate medication was most strongly associated with polypharmacy (odds ratio 4.992).Conclusions: The present findings showed that polypharmacy was quite common among the elderly home‐care patients, and they suggest that home‐care physicians should prescribe fewer medications in accord with the deterioration of home‐care patients’ general condition. Geriatr Gerontol Int 2018; 18: 33–41.