Abstract
BACKGROUND: This study examines epidemiology and trend of mortality rates due to traffic accidents in Iran from 2006 to 2022. METHODS: Data were collected from the Iranian Legal Medicine Organization and the Statistical Center of Iran. Age-standardized mortality rates were calculated using direct standardization. A Latent Class Growth Mixture Model (LCGMM) was employed to evaluate trends and identify provinces with similar patterns. RESULTS: From 2006 to 2022, Iran recorded 325,851 traffic accident deaths, with a median age of 34 years; 78.8% were male. Most deaths occurred on intercity roads (63.84%, n = 208,021), followed by urban roads (27.73%, n = 90,365) and rural roads (7.63%, n = 24,859). Mortality rates declined significantly from 38.86 per 100,000 in 2006 to 19.85 in 2017 but increased to 23.00 per 100,000 in 2022, underscoring a concerning public health issue. A reverse J-shaped trend was identified nationally using LCGMM, showing an initial decline (intercept: 48.13, SE = 1.32; slope: -3.67, SE = 0.34) followed by a significant upward trend (quadratic term: 0.14, SE = 0.02, p < 0.001). The quadratic term's highly significant p-value highlights the importance of this non-linear pattern. At the provincial level, six distinct mortality trend classes were identified, highlighting significant regional variations. Most provinces exhibited a reverse J-shaped pattern, except Sistan and Baluchestan and Kohgiluyeh and Boyer-Ahmad, which showed U-shaped trends. CONCLUSION: After a decade of decline (2006-2017), Iran's traffic fatalities resurged post-2017, potentially linked to economic strain, aging vehicle fleets, and inconsistent enforcement of safety regulations. Targeted interventions -subsidies for safer vehicles, infrastructure upgrades, and regional policies- are urgently needed to reverse this trend and align with global road safety goals.