Epidemiology and association of neighbourhood marginalisation on violent knife assaults in Ontario: a population-based case-control study.

Background: Violent knife assaults ('stabbings') are underappreciated as a source of morbidity and mortality. The two objectives of this study were to describe the epidemiology of stabbing injuries in the population of Ontario, Canada and to assess the associations between two measures of neighbourhood marginalisation-material deprivation and housing instability, and the risk of stabbing injury.

Methods: We conducted a population-based case-control study over 2004-18 using linked administrative data. Cases suffered a stabbing injury resulting in an emergency department visit, hospitalisation or death. Four age and sex-matched controls were matched to each case. Multivariate logistic regression was used to assess the associations between neighbourhood material deprivation as well as housing instability and the risk of injury. Mean annualised injury incidences were estimated using the number of cases identified divided by the total population of Ontario for that year.

Results: We identified 26 657 individuals with a stabbing injury, of which 724 (2.7%) were fatal. The mean annualised incidence was 13.4 per 100 000 (95% CI: 12.7 to 15.9). Victims were disproportionately young (median age 25 years; IQR: 20-37 years) males (84.1%), from large urban centres (77.5%), and in the lowest income quintile (39.3%). In multivariate models, neighbourhood material deprivation (OR 1.45, 95% CI: 1.43 to 1.47) and housing instability (OR 1.4, 95% CI: 1.22 to 1.26) were associated with risk of injury.

Conclusions: Stabbing injuries are a substantial public health problem that affects individuals of all ages and demographics but disproportionately affects younger men in urban settings. There is a weak association between residence in marginalised neighbourhoods and the risk of stabbing injury. Future studies should aim to better understand the nature of this association and consider opportunities for public health interventions to reduce the burden of violent knife injuries.