Objective: To explore the temporal trend of incidence, causes of injury and main characteristics of adolescent and adult subjects with mild head injury (MHI).

Design: This study had a retrospective design.

Setting: The study was conducted in a longitudinal database of an Italian Emergency Department (ED).

Participants: The study comprised 19124 consecutive subjects who visited and were managed within 24 h from the event, according to a predefined protocol for MHI from 1997 to 2008.

Main outcome measures: Incidence, demography, cause of injury and characteristics of any post-traumatic intracranial lesion within 7 days from MHI.

Results: The number of subjects with MHI decreased from 2019 per year (1997-1999) to 1232 per year (2006-2008; P for linear trend <0.001), without differences in the total number of subjects visited in the ED. The decrease was observed in all age-decades, in particular, in subjects in the age ranges of 20-29 and 30-39 years. Over time, the age of subjects with MHI lost a bimodal distribution, and the mean age increased from 43 (25-69) years (median (interquartile range)) in 1997-1999 to 56 (33-78) years in 2006-2008 (P<0.001). The prevalence of falls increased from 36.5% to 55.0%, whereas crashes fell from 53.2% to 31.9%. The incidence of subdural haematoma (SDH) and epidural haematoma (EDH) did not change over time, whereas traumatic subarachnoid haemorrhage (t-SAH) and intra-cerebral haematoma/brain contusion (ICH) increased (from 0.7% to 1.9% and from 2.5% to 3.2%; P for trend: <0.001 for both.

Conclusions: The incidence and the clinical characteristics of MHI subjects are rapidly changing in our setting. These data need to be considered in defining the effectiveness of preventive measures and deciding resource allocation.