Trends in the use of seat belts and mobile phones and their seasonal variations in Florence (2005-2015)

Introduction About 1.25 million people worldwide die every year because of road accidents. Risk is higher when drivers use mobile phones, whereas seat belts help to prevent crash-related injury. We aimed to evaluate the prevalence, associated factors, and temporal trend of the use of seat belts and mobile phones among drivers and passengers in Florence, Italy (2005–2015). Methods Use of seat belts and mobile phones use was monitored via direct observation in four areas in the province of Florence. We fitted Poisson regression models with robust variance to investigate the factors associated with the use of seat belts and mobile phones use by the drivers and to explore long-term trends and seasonal patterns in the two time-series. Results We observed a total of an overall 134,775 vehicles: seat belts were worn by 71.8% of drivers and front-seat passengers and 27.6% of back-seat passengers, while mobile phones were being used by 4.8% of drivers. Drivers were more likely to wear seat belt when transporting passengers (�2 vs none: prevalence ratio [PR] 1.21, 95% confidence intervals [CI] 1.14– 1.29) and while driving in the afternoon (PR 1.04, 95% CI 1.03–1.05), and less likely when the front-seat passenger was not wearing seat belts (PR 0.33, 95% CI 0.32–0.34). After an initial increase, seat belts use by the driver decreased over time (-0.5% each year during 2010–2015), with significant peaks and troughs in July and January, respectively. Mobile phone use by the driver was inversely associated with wearing seat belts (PR 0.67, 95% CI 0.64–0.70) and carrying passengers (�2 vs. none PR 0.20, 95% CI 0.07–0.52). The proportion of drivers using mobile phones did not vary over time nor showed any clear seasonality.