Cancer diagnosis negatively affects medication adherence in glaucoma patients

Medication adherence in patients with glaucoma drops following a cancer diagnosis, as reported in a recent study.

The study used data from the Taiwan National Health Insurance and followed 4,001 patients with confirmed glaucoma in one or both eyes and who was diagnosed with cancer. Participants were then matched with a group of 8,002 glaucoma patients who did not develop cancer.

Researchers assessed medication adherence using the medication possession ratio (MPR), which measured for a period rather than at a particular time point. Four years was used to determine changes in MPR, up to 2 years before and after cancer diagnosis.

MPR appeared to be the highest in both the cancer and control groups when measured at 1-year intervals, with corresponding values of 0.379 (95 percent confidence interval [CI], 0.370–0.388) and 0.313 (95 percent CI, 0.308–0.319).

In the cancer group, MPR was consistently higher before the index date and lower after cancer diagnosis across all measures used (1-year, 2-year and 2-year-average intervals). On the other hand, the change in MPR in the control group was not evident and varied in the three different measures of MPR.

On difference-in-difference analysis, a cancer diagnosis reduced medication adherence in glaucoma patients by 17.4 percent when MPR was measured using 1-year intervals (p<0.001), by 10.4 percent when using 2-year intervals (p<0.001), and by 9.21 percent when using 2-year-average intervals (p<0.001).

In light of the findings, the researchers recommended developing policies directly targeting the burden associated with having cancer that tends to create barriers for medication refills instead of targeting risk factors that also apply to cancer-free patients with glaucoma.