Medication adherence in patients with dementia: an Austrian cohort study.

Sustained treatment with effective doses of cholinesterase inhibitors or memantine is crucial to transfer treatment effects in dementia. Numerous studies, with often small samples sizes, describe low adherence rates. The purpose of current study was to examine the medical adherence of antidementia therapy in Austria. We analyzed the data of 10 Austrian Health Insurance Funds, including treatment-naive dementia patients. Study outcome measures were discontinuation, switching, number of days on therapy, Medication-Possession-Ratio, and compliance. A total of 15,809 patients (mean age: 79.9 y, female: 67.3%) met the study's inclusion criteria. After stratification by index medication there were 40.3% on donepezil (n=6371); 26.6% on rivastigmine (n=4206); 15.3% on galantamine (n=2424); and 17.8% on memantine (n=2808). After 6 and 12 months on therapy, 5376 (34.0%) and 9243 (58.5%) patients stopped the initially prescribed antidementia therapy; after 12 months the highest discontinuation rate was seen for patients taking rivastigmine (67.3%), whereas patients on memantine (45.0%) had the lowest. After 12 months, a total of 1874 (11.9%) patients switched from their index medication to another cholinesterase inhibitor or memantine. A total of 6163 patients (39.0%) were compliant (Medication-Possession-Ratio >80%) during the first 6 months and 5366 patients (33.9%) during 12 months of the study. Our study shows that memantine-treated patients adhere significantly better to treatment. Specifically, after 12 months, 45.0% discontinued medication, 7.9% switched, and 50.8% of patients on therapy were compliant.