Cost-Related Underuse of Medicines for Asthma-Opportunities for Improving Adherence.

Background: In asthma, underuse of cost-effective preventive treatments increases morbidity and mortality. The cost of medicines contributes to underuse ("nonadherence"), but the extent to which people with asthma skip or reduce doses or let prescriptions go unfilled when faced with cost pressures is unknown.

Objective: To estimate the extent of cost-related underuse behaviors and associated factors.