Motor vehicle accident mortality by elderly drivers in the super-aging era: A nationwide hospital-based registry in Japan

Motor vehicle accidents (MVAs) are one of the major public health burdens worldwide. In particular, MVAs by elderly drivers have been significantly increasing in recent years in industrialized countries. This study aimed to assess the MVA characteristics and outcomes caused by elderly drivers in Japan. Japan Trauma Data Bank (JTDB) is a prospective, nationwide, hospital-based registry for trauma patients from 256 institutions in Japan. This study enrolled all MVA drivers older than the legal age for driving between 2004 and 2015. The included patients were divided into the following 3 groups: adults (aged ≤64 years), young-old (aged 65–74 years), and old-old (aged ≥75 years). The primary outcome was in-hospital mortality. The trend in the proportion of MVAs caused by the young-old or the old-old group was evaluated using the Cochran–Armitage trend test. To assess the association of the old-old group with in-hospital mortality, compared with the adult group, we used multivariable logistic regression analysis. During the study period, a total of 236,698 trauma patients were registered, and 39,691 patients (16.8%) were eligible for our analysis. The proportion of MVAs caused by elderly drivers aged ≥65 years significantly increased from 11.7% in 2004 to 23.8% in 2015 (P < .001). As for the primary outcome, unadjusted in-hospital mortality increased with age, but decreased year-by-year irrespective of the age group. In multivariable logistic regression analysis, in-hospital mortality was significantly higher in the old-old group than in the adult group [17.3% (584/3372) vs 8.0% (2556/31,985); adjusted odds ratio 4.80; 95% confidence interval 4.06–5.67]. In the super-aging society of Japan, the proportion of MVAs by elderly drivers increased year-by-year, and the mortality rate was highest in those aged above 75 years.