Accident or suicide? New registration procedures and improved classification of suicide vs accident deaths on the Swedish railways: an interrupted time series analysis of years 2000–2023

• New procedures were implemented to better resolve suicide vs accident deaths at the railways. • The fraction of classified suicides vs accidents increased significantly over time, when the new procedures were implemented. • Decreasing accident deaths drove the effect, while suicides stopped rising after year 2016 • Fewer undetermined deaths among the official accident counts played a major role for the effect • Reliable death classification on the railways enables better preventive efforts and evaluation of their effects Death by suicide is a major societal issue, affecting railways in particular. However, the numbers of suicides have likely been underestimated, by being misclassified as accidents. In the year 2016, Sweden finalized the introduction of more extensive investigation procedures to resolve more deaths by suicide. Before year 2016, railway fatalities with undetermined suicidal intent were simply classified as accidents by default, unless forensic autopsies or police decided otherwise. During the years 2016–2023, all fatalities were evaluated by using a special investigation form and undetermined or drug use deaths were further investigated by a psychosocial investigator. An expert group then classified these deaths as suicide or accident. We evaluated the effect of these altered procedures by interrupted time series (ITS) models using the official statistics concerning the percentage of deaths reported as suicides (%suicides). Over the entire study period, %suicides increased from ∼75 % to ∼87 %. Using ITS models accounting for a roll-in implementation period (2012–2016), displayed the best fit compared to alternative competing models, as well as a significant increase of %suicides by at least ∼4 % during the period after 2016 per se and ∼10 % if including the roll-in period. The effect after 2016 was mediated by a decline in the official accident counts, but more detailed classification data suggested that this was rather due to a reduction of undetermined causes of deaths. We conclude that the more extensive classification procedures reduced the misclassification of suicides as accidents, whereby we recommend its continued usage.