Changes in Healthcare Spending After Diagnosis of Comorbidities Among Endometriosis Patients: A Difference-in-Differences Analysis

INTRODUCTION We sought to characterize changes in healthcare spending associated with the onset of 22 endometriosis-related comorbidities. METHODS Women aged 18-49 years with endometriosis (N = 180,278) were extracted from 2006-2015 de-identified Clinformatics® DataMart claims data. For 22 comorbidities, comorbidity patients were identified on the basis of having a first comorbidity diagnosis after their initial endometriosis diagnosis. Controls were identified on the basis of having no comorbidity diagnosis and were matched 1:1 to comorbidity patients on demographics and baseline spending. Total medical and pharmacy spending was measured during 12 months before and after each patient's index date (first comorbidity diagnosis for comorbidity patients, and equal number of days after earliest endometriosis claim for controls). Pre-post spending differences were compared using difference-in-differences linear regression. Total and comorbidity-related cumulative spending per patient for all endometriosis patients were calculated annually for the 5 years following endometriosis diagnosis. RESULTS The number of endometriosis patients with each comorbidity varied between 121 for endometrial cancer and 16,177 for fatigue. Healthcare spending increased significantly with the onset of eight comorbidities: breast cancer, ovarian cancer, pregnancy complications, systemic lupus erythematosus/rheumatoid arthritis/Sjogren's/multiple sclerosis, infertility, uterine fibroids, ovarian cyst, and headache [p < 0.001 except for headache (p = 0.045)]. Spending decreased significantly for fatigue, cystitis/UTI, and eczema [p < 0.001 except for fatigue (p = 0.048)] and was not statistically different for the other 11 comorbidities. Difference-in-differences estimates were significantly higher for comorbidity patients for all comorbidities except eczema (p ≤ 0.003). Mean 5-year total cumulative spending was $58,191 per endometriosis patient, of which between 11% and 23% was attributable to comorbidity-related medical claims. CONCLUSION For all but one of the 22 comorbidities associated with endometriosis, comorbidity onset was associated with a relative increase in total healthcare spending. FUNDING AbbVie Inc.