Adherence to treatment linked to better outcomes, but little is known about interventions to improve adherence

May 1, 2010

Medication adherence is obviously an important determinant to the success of treating many chronic diseases, just as poor adherence can lead to negative outcomes.

Medication adherence is an important determinant of the success of treating many chronic diseases, just as poor adherence can lead to negative outcomes.

In the case of osteoporosis medications, both hospital admissions for fracture and medical costs are related to treatment adherence, and women who were less satisfied with their treatment were more likely to discontinue or switch their therapy.

Rachel Halpern, PhD, associate director at i3 Innovus in Eden Prairie, Minnesota, and colleagues presented their review of medical and pharmacy claims data from 32,573 women with osteoporosis who were 45 years or older and enrolled in a large US health plan. They measured adherence by the medication possession ratio (MPR), a formula that determines compliance from the first to the last prescription.

Mean monthly medical costs were $405 among the group with high adherence, which was significantly lower than among those with medium adherence ($466; P=.002) and low adherence ($507; P<.001). After adjustment, mean medical costs were 11.4% higher (P=.001) for women with high versus low adherence.

Adherence falls, fractures rise

At the 2009 meeting of the American College of Rheumatology in Philadelphia, Halpern revealed that low adherence to osteoporosis therapy (ie, alendronate, risedronate, teriparatide, ibandronate, or raloxifene) was associated with a significantly increased risk of fracture.

Using medical and pharmacy claims data from 88,122 women, she again used the MPR to classify adherence to osteoporosis therapy, but this time assessed fractures up to 2 years after the date of the women's first medication claim. She found that those with low adherence had an 8.3% higher fracture risk than those with high adherence (P=.0110) when adjusting for covariates.

Treatment satisfaction was linked to adherence with osteoporosis therapy, according to data from an observational study presented at ASBMR by Elizabeth Barrett-Connor, MD, professor of medicine and chief of the division of epidemiology, Department of Family and Preventive Medicine, University of California, San Diego, and colleagues.

The investigators asked 2,402 postmenopausal women being treated with a single drug for osteoporosis to complete the Treatment Satisfaction Questionnaire for Medication (TSMQ), which uses scores of 0 to 100 on 4 domains of patient satisfaction, with higher scores indicating greater satisfaction. Three-fourths (77%) of the women were being treated with a bisphosphonate.

Five hundred ninety-one women discontinued therapy, and another 171 switched their initial treatment. Women who were less satisfied with the convenience of their treatment (TSMQ domain score in the lower 50%) were 28% more likely to discontinue or switch their initial therapy than those who were more satisfied with the convenience of their treatment (TSMQ domain score in the upper 50%). The same patterns were evident for TSMQ satisfaction scores for the effectiveness, global satisfaction, and side effects domains.

Little data on the efficacy of interventions to improve adherence have been published. A recent Cochrane Review of 11 such studies attempted to assess the effectiveness of interventions to improve adherence to lipid-lowering therapy and found that simply reminding patients to take their medication improved adherence by 6% to 24% in 4 of the 6 clinical trials to assess this type of intervention (Cochrane Database Syst Rev. 2010;3:CD004371). Simplifying the drug regimen and providing patient education materials were also associated with increased adherence.