[Causes of dementia and bed-ridden state in elderly victims of road traffic accidents in Japan].

BACKGROUND

In Japan, autopsies are seldom performed for the victims of road traffic accidents (RTA). Thus, when an elderly RTA victim dies after long-term hospitalization, the actual cause of death is hard to determine.

SUBJECTS

Eight hundred eleven road traffic victims (69 +/- 16 years, M/F = 592/219) for whom insurance companies required us to judge the medical causal relation between the accident and the death from the view point of clinical forensic medicine.

METHODS

We discussed and reevaluated the cause of death and decided the cause and effect relation based on medical information.

RESULTS

The number of subjects was equivalent to 8.4% of the yearly deaths by RTA in the investigated area, 19.3% of the aged death by RTA. An autopsy was performed only for 5%, ISS was 17.0 +/- 11.5; 94% were hospitalized; 62% continued to be unconscious, involving dementia (32%), persistent vegetative state (17%), coma or semi-coma (13%). Of the cases investigated, 89% died after becoming bedridden, which in 87% of cases was due to the RTA. The odds ratios of a bedridden state for head AIS > = 3, lower limbs AIS > = 2, lower limbs AIS > = 3, spinal AIS > = 3, chest AIS > = 2 were 3.1, 3.2, 7.2, 2.5, 1.8, respectively. The odds ratios of dementia for head AIS > = 3, head AIS > = 4, chest AIS > = 4 were 29.2, 35.9, 1.2, respectively. Patients with head injuries were more likely to be bedridden and senile, and patients with leg fractures tended to be bedridden, particular in the aged. When elderly traffic victims became bedridden or senile, most of them, 399 bedridden victims and 53 non-bedridden victims, died within 242 +/- 283 days, and 356 +/- 284 days from the RTA, respectively. The cause of death could be classified into five categories; pneumonia, other infection, malnutrition and/or dehydration, malnutrition and/or dehydration with pneumonia, malnutrition and/or dehydration with other infection. Traffic deaths were recorded on 31% of death certificates, but were 77% by our reevaluation (p < 0.00001), because the cause-of-death can be difficult to determine in elderly traffic victims. Logistic regression was used to calculate the risk of dementia caused by bone fractures after adjusting for age and gender. The risk of dementia due to bone fractures was influenced by the number of the long fractured bones, a high age group, a lower ADL, and a past history of dementia. Thus, we speculate that traumatic dementia based on bone fractures may occur.