Factors associated with adherence to drug therapy: a population-based study.

Objective: To investigate adherence to prescription in a female population aged 35-65 years.

Design: Postal questionnaire study of 2991 randomly sampled 35- to 64-year-old women in seven provinces of central Sweden.

Methods: The study was performed in 1995 as a cross-sectional postal questionnaire study in seven counties in central Sweden. The questionnaire was sent to a random sample of 4200 women between the ages of 35 and 64, of whom 2991 (71.2%) responded. The questionnaire asked about drugs prescribed during the past year and about factors potentially affecting adherence.

Results: The same women had different degrees of adherence to different medications. A large number of factors were associated with adherence. Multivariate analysis revealed that age, scheduled check-up, perceived importance of medication, concerns about medication safety and taking medication for a respiratory or a cardiovascular disease were significantly related to adherence. Adherence ranged from 15-98% depending on these factors, and was the lowest among young women who regarded their medication as unimportant and who had no scheduled check-up; the highest reported adherence was found among elderly women who regarded their medication as important and who had a scheduled check-up.

Conclusion: Factors that were associated with the perceived importance of medication had a positive effect on adherence, while concerns about medication safety had a negative effect.