The association of adherence to osteoporosis therapies with fracture, all-cause medical costs, and all-cause hospitalizations: a retrospective claims analysis of female health plan enrollees with osteoporosis.

Abstract

Osteoporosis affects approximately 10 million people in the United States and is associated with increased fracture risk and fracture-related costs. Poor adherence to osteoporosis medications is associated with higher general burden of illness compared with optimal adherence. To examine the associations of adherence to osteoporosis therapies with (a) occurrence of closed fracture, (b) all-cause medical costs, and (c) all-cause hospitalizations. This retrospective analysis of administrative claims data examined women with osteoporosis initiating therapy with alendronate, risedronate, ibandronate, or raloxifene from July 1, 2002, to March 10, 2006. Data were from a large, geographically diverse U.S. health plan that covered about 12.6 million females during the identification period. Commercially insured and Medicare Advantage plan enrollees were observed for 1 year before (baseline period) and 540 days after therapy initiation (follow-up period). Outcomes included closed fractures, all-cause medical costs, and all-cause hospitalizations; all outcomes were measured starting 180 days after therapy initiation through follow-up. All subjects had at least 2 pharmacy claims for any of the targeted osteoporosis medications. Adherence was measured with a medication possession ratio (MPR) and accounted for all osteoporosis treatment. High adherence was MPR of at least 0.80; low adherence was MPR less than 0.50. Covariates included baseline fracture, "early" fracture (in the first 180 days of follow-up), baseline corticosteroid or thyroid hormone use, health status indicators, and demographic characteristics. Outcome fractures were modeled with Cox survival regression with time-dependent cumulative MPR. All-cause medical costs and all-cause hospitalizations were modeled, respectively, with generalized linear model regression (gamma distribution, log link) and negative binomial regression. The sample comprised 21,655 patients--16,295 (75.2%) commercial and 5,360 (24.8%) Medicare Advantage. During the entire follow-up period, 5,406 (33.2%) and 2,253 (42.0%) of commercial and Medicare Advantage patients, respectively, had low adherence. Adherence tended to decrease over the follow-up period. The Cox regression showed that commercial plan patients with low versus high adherence had 37% higher risk of fracture (hazard ratio = 1.37, 95% CI = 1.12-1.68). Adherence was not significantly associated with fracture in the Medicare Advantage cohort. Commercial and Medicare Advantage patients with low versus high adherence had 12% (exponentiated coefficient = 1.12, 95% CI = 1.02-1.24) and 18% (exponentiated coefficient = 1.18, 95% CI = 1.04-1.35) higher all-cause medical costs during months 7 through 18 of follow-up. Commercial and Medicare Advantage patients with low versus high adherence had 59% (incidence rate ratio [IRR] = 1.59, 95% CI = 1.38-1.83) and 34% (IRR = 1.34, 95% CI = 1.13-1.58) more all-cause hospitalizations during months 7 through 18 of follow-up, respectively. Low adherence to osteoporosis pharmacotherapy was associated with higher risk of fracture for commercially insured but not Medicare Advantage patients and with higher all-cause medical costs and more all-cause hospitalizations in both groups. These results are consistent with the literature and highlight the importance of promoting better adherence among patients with osteoporosis.