The motorcycle mortality transition in Brazil: a nationwide ecological time-series study

Background Rapid motorcycle fleet expansion has profoundly altered patterns of transport-related mortality in many low- and middle-income countries. Brazil has experienced one of the world’s largest increases in motorcycle use over the past two decades; however, nationwide evidence characterizing the long-term transition from pedestrian- to motorcycle-dominated transport mortality remains limited. This study aimed to characterize the nationwide transition from pedestrian- to motorcycle-dominated transport mortality and its regional heterogeneity in Brazil between 2004 and 2024. Methods We conducted a nationwide ecological time-series study using official mortality data from the Brazilian Mortality Information System (SIM/DATASUS). Transport-related deaths were classified according to ICD-10 road-user categories, and annual population estimates from the Brazilian Institute of Geography and Statistics (IBGE) were used to calculate mortality rates. Following formal assessment of Poisson model assumptions, negative binomial regression was adopted as the primary inferential approach. Segmented regression was performed as a sensitivity analysis to identify temporal changes in mortality trends. Regional heterogeneity was evaluated using pooled models with calendar year × geographic region interaction terms. Exploratory ecological analyses assessed the relationship between motorcycle fleet expansion and mortality trends using official data from the Brazilian National Traffic Secretariat (SENATRAN). Results Between 2004 and 2024, Brazil recorded 756,633 transport-related deaths, including 227,409 motorcycle occupant fatalities, becoming the leading category of transport-related mortality during the study period. Motorcycle mortality increased from 2.75 to 7.27 deaths per 100,000 inhabitants, whereas pedestrian mortality declined from 5.54 to 2.67 deaths per 100,000 inhabitants, demonstrating a nationwide transition from pedestrian- to motorcycle-dominated transport mortality. Adjusted analyses showed an average annual increase of 3.2% in motorcycle mortality (IRR 1.032, 95% CI 1.020–1.043) and an average annual decrease of 4.3% in pedestrian mortality (IRR 0.957, 95% CI 0.952–0.961). Segmented regression identified distinct temporal phases, and regional analyses demonstrated significantly faster increases in motorcycle mortality in the North and Northeast than in other Brazilian macroregions. Exploratory ecological analyses showed that motorcycle fleet expansion was positively associated with the observed temporal trends. Conclusions Brazil underwent a nationwide transition from pedestrian- to motorcycle-dominated transport mortality between 2004 and 2024, accompanied by marked regional heterogeneity and rapid motorcycle fleet expansion. These findings provide robust nationwide evidence on the changing epidemiology of transport-related mortality in Brazil and support the development of regionally tailored road safety policies and integrated injury surveillance strategies in rapidly motorizing middle-income countries.