This is an exploratory study using a mathematical model applied to databases from 204 countries on outpatient, emergency, home and inpatient care. From what these data sources record, the author calculates the trend in the incidence of adverse events to medical treatments (AEMT) from 1990 to 2019, i.e. unwanted adverse events resulting from a procedure, treatment or other contact with the health system. 

As the study is not based on direct collection of primary data from patients, it should be interpreted with caution. In addition, under-reporting of AEMT traditionally exists, especially in low-income countries, and their incidence is shaped by multiple factors that are not easy to control for. 

Despite these limitations, the study is based on the Global Burden of Disease (GBD) Study, which is the most comprehensive source of information on levels and trends in health loss due to disease and injury worldwide. The author applies sophisticated methods of analysis that allow him to compare the occurrence of AEMT between high- and low-income countries, irrespective of age differences, secular trends and birth cohort effects (the generation in which each person is placed). 

Adverse events to medical treatments have become a major public health problem worldwide. They rank among the leading causes of preventable mortality in both developed and low-income countries. 

The study provides estimates of the time trend of the incidence rate of AEMT between 1990 and 2019 globally, according to the socio-economic development of the country and by age group. 

From 1990 to 2019, the total number of AEMT increased from 11.3 million to 18.0 million, an increase of 59.3 %, outpacing population growth of 44.6 % over the same period. The incidence rate of AEMT for all ages was 232.5 per 100,000 population in 2019, representing an increase of 10.1 per cent over the past 30 years, observed mainly among the older population. This represents a net growth in the overall incidence rate of 0.631 % per year, despite the global implementation of policies that prioritise patient safety. 

The implications of these findings are that as the ageing of the world's population intensifies, along with the increasing amount of health services provided, measures need to be taken to address the continually growing burden of AEMT. 

The study provides essential information to prioritise resources and implement more specific preventive strategies for AEMT, emphasising the importance of improving the optimisation of geriatric medical management to reduce iatrogenic harm. 

As discussed, the main limitations lie in the measurement of adverse effects of medical treatments. This is especially relevant in low-income countries, which lack reliable original data on AEMT and the incidence estimates provided by predictive models still have uncertainties. 

The study only assesses the overall incidence of AEMT, with no data on the types of adverse events and their severity (impact on health, quality of life and mortality).