When temperatures rise: Assessing the association between daily maximum temperature and nonfatal assault hospital visits during New York City summers, 2016–2021

Background: Research suggests hot temperatures are associated with violent incidents, raising concerns about worsening violence with climate change. We sought to quantify the association between elevated daily maximum temperatures and rates of nonfatal assault hospital visits in New York City. Methods: We analyzed 126,304 nonfatal assault-related hospital records during warm months (May–September), 2016–2021 using the International Classification of Diseases-, Tenth Revision, Clinical Modification codes and distributed lag nonlinear negative binomial models, accounting for time-varying confounders. Results: Our analysis found that the rate of nonfatal assault hospital visits increased with temperature to 32.2°C then declined at greater temperatures in an inverted U-shaped association. The peak cumulative rate ratio was 1.76 (95% CI: 1.53–2.03) using a 0–5-day lag, relative to 9.4°C, the lowest observed warm-season daily maximum temperature. Conclusions: Our results support the hypothesis that temperature is associated with social interactions, including violence. While inconclusive on the full nature of extreme heat impacts on increased assault hospital visits, our findings illustrate one aspect of the relationship between increased temperature and violence, providing a foundation for future studies exploring the influence of environmental conditions on incidence of assault.