A comprehensive review of official discount rates in guidelines of health economic evaluations over time: the trends and roots.

Background: The question of discounting in health economics is anything but settled, so much so that a section of the Health Technology Assessment (HTA) guidelines is devoted to it.

Objective: This study aimed to review the trend of the value of the official discount rates (DRs) of costs and health outcomes and their roots worldwide.

Methods: Four methods were combined to identify official DRs over time globally. These methods included a systematic review of the HTA/pharmacoeconomic/health economic evaluation guidelines, a review of methodological documents or guidelines accessible on the websites of HTA organizations, and two separated reviews of the websites of the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) and the Guide to Health Economic Analysis and Research (GEAR).

Results: Our systematic search eventually yielded 339 documents from the literature, 35 links from the website of the HTA organizations, 51 documents from the website of the ISPOR, and 29 documents from the website of the GEAR. These documents referred to 48 countries over 30 years and 43 transnational guidelines over 43 years. DRs of 3% and 5% had the most frequent value. Among them, 38 countries always used an equal DR of costs and health outcomes. We categorized the rationales for selecting DRs into eight groups for the national documents and six groups for the transnational documents.

Conclusion: The comparability approach was the most frequent rationale for choosing the DR in national and transnational guidelines. The value of DR of costs and health outcomes ranged from zero to 10% over the years, but the most common values were 3% and 5%, mainly arising from the comparability approach chosen. Several transnational guidelines have suggested a specific DR without taking into account countries' economic conditions. It is useful to establish a specific guideline for calculating and updating the DR of the health sector in each country.