The spread of the coronavirus disease 2019 (COVID-19) pandemic caused a sudden and significant disruption in healthcare services, especially for patients suffering from chronic diseases. We aimed at evaluating the impact of the pandemic on adherence to chronic therapies through a systematic review of available studies. PubMed, EMBASE, and Web of Science were searched since inception to June 2022. Inclusion criteria were: (1) observational studies or surveys; (2) studies on patients with chronic diseases; (3) reporting the effects of COVID-19 pandemic on adherence to chronic pharmacological treatment, as a comparison of adherence during the pandemic period vs. pre-pandemic period (primary outcome) or as rate of treatment discontinuation/delay specifically due to factors linked to COVID-19 (secondary outcome). Findings from 12 (primary outcome) and 24 (secondary outcome) studies showed that many chronic treatments were interrupted or affected by a reduced adherence in the pandemic period, and that fear of infection, difficulty in reaching physicians or healthcare facilities, and unavailability of medication were often reported as reasons for discontinuation or modification of chronic therapies. For other therapies where the patient was not required to attend the clinic, continuity of treatment was sometimes ensured through the use of telemedicine, and the adherence was guaranteed with drug stockpiling. While the effects of the possible worsening of chronic disease management need to be monitored over time, positive strategies should be acknowledged, such as the implementation of e-health tools and the expanded role of community pharmacists, and may play an important role in preserving continuity of care for people with chronic diseases.
Keywords: COVID-19 pandemic; chronic therapies; epidemiology; healthcare system; medication adherence.