The economic impact of comorbidity in multiple sclerosis

Comorbid conditions are common in people with multiple sclerosis (pwMS). They can delay diagnosis and negatively impact the disease course, progression of disability, therapeutic management, and adherence to treatment.Objective: To quantify the economic impact of comorbidity in multiple sclerosis (MS), based on cost-of-illness estimates made using a bottom-up approach.Methods: A retrospective study was carried out in two northern Italian areas. The socio-demographic and clinical information, including comorbidities data, were collected through ad hoc anonymous self-assessment questionnaire while disease costs (direct and indirect costs of disease and loss of productivity) were estimated using a bottom-up approach. Costs were compared between pwMS with and without comorbidity. Adjusted incremental costs associated with comorbidity were reported using generalized linear models with log-link and gamma distributions or two-part models.Results: 51.0% of pwMS had at least one comorbid condition. Hypertension (21.0%), depression (15.7%), and anxiety (11.7%) were the most prevalent. PwMS with comorbidity were more likely to use healthcare resources, such as hospitalizations (OR = 1.21, p < 0.001), tests (OR = 1.59, p < 0.001), and symptomatic drugs and supplements (OR = 1.89, p = 0.012), and to incur non-healthcare costs related to investment (OR = 1.32, p < 0.001), transportation (OR = 1.33, p < 0.001), services (OR = 1.33, p < 0.001), and informal care (OR = 1.43, p = 0.16). Finally, they experienced greater productivity losses (OR = 1.34, p < 0.001) than pwMS without comorbidity. The adjusted incremental annual cost per patient due to comorbidity was €3,106.9 (13% of the overall costs) with MS disability found to exponentially affect annual costs.Conclusion: Comorbidity has health, social, and economic consequences for pwMS.