A head injury can blight the chances of survival up to 13 years after the event, especially among younger adults, finds research published online in the Journal of Neurology Neurosurgery and Psychiatry.
Injury severity seems to make little difference over the longer term, the findings show.
The research team tracked over 2,000 people, 757 of whom had sustained a head injury that required admission to one of five hospitals in Glasgow between 1995 and 1996.
The rest of the group were split between those who had been admitted to hospital for other reasons, but for the same period as those with a head injury, and healthy people living in the community. The three groups were matched for age, gender, and levels of deprivation.
In all, 40% of people (305) who had sustained a head injury were dead within 13 years of the event. This was higher than the rate among those admitted with other injuries (28%) and those in the community, almost one in five of whom died (19%).
Although the heightened risk of death was highest in the first year after injury, it persisted for at least a further 12 years, when the head-injured were almost three times as likely to die of circulatory, respiratory, digestive, psychiatric and external causes as their community peers.
Those who had sustained other injuries were also more likely to die of these causes, but the risk was not as high.
The annual rate of death from all causes among the head-injured was almost 31 per 1,000 people compared with just under 14 per 1,000 for those living in the community.
As might be expected, those with more serious injuries were more likely to die than those with mild injuries during the critical first year. But those with mild head injury were also twice as likely to die.
And more than a year later, the young and middle aged were far more likely to die than those who were older, when compared with those with no head injury.
Deaths among those aged 15 to 54 were more than six times higher than rates among those without a head injury, irrespective of potentially influential factors, such as gender and level of deprivation.
Lifestyle factors before the injury, such as excessive alcohol intake and living alone or a history of mental health problems do affect survival, say the authors. But these factors also feature among those admitted for other injuries.
There are no clear explanations for the higher death rates among the young and middle aged, say the authors.
"The reason for greater vulnerability in younger adults is unclear, but requires further consideration, especially given the particularly higher risk of head injury in younger adults," they say. Head injury accounts for most trauma deaths in this age group, the evidence shows.