The traffic issues have been attracting global attention due to increased occurrence and higher mortality rate in the older population. Many countries have employed different kinds of regulations on the elder drivers depending either on their age or whether being demented. These policy differences left a research gap to identify the temporal relationship between serious traffic accidents (STA) and dementias, which can inform the most appropriate time for policymaking. In the present study, we linked two national databases and performed analyses to explore this problem.

With the grant and supports from the government, the research team combined the databases of STA registries and the whole population dataset of National Health Insurance Research Database to form a 10-year retrospective cohort for analyses. We performed both retrospective and prospective directions to explore the time length between STAs and the diagnoses of dementia depending on the selection of the STA occurrences and dementia diagnoses as outcomes. In addition to descriptive statistical analyses, we also performed inferential statistics to analyse the variables between different types of STAs. A p-value less than 0.05 was set as statistically significant.

437516 persons involved in STAs were enrolled for analyses and the mean age was 61.47 years (SD=8.90) with sex ratio (F/M) of 0.62. We divided the samples into three groups: (1) STAs without dementias (95.17%) (2) dementias after STAs (3.40%), and (3) dementias before STAs (1.43%). The mean age of the 3rd group (73.80 years, SD=8.79) was significantly older than the rest two. When comparing these three groups, a preceded dementia diagnosis was a significant risk factor for repeated STAs. (OR: 1.205, 95% CI: 1.100-1.320, p<0.001) Finally, an average length of 2.35 years (SD: 1.60) was found for those who was diagnosed of dementias before the first STA while 2.57 years (SD: 1.69) was noted for the diagnosis of dementia after first STA.

In our study, dementia was identified as a significant risk factor for STAs. We further asserted that 2.5 years would be an appropriate time length for the authorities to examine the traffic risks of those who were diagnosed of dementias.