Sickness absence, disability pension, and permanent medical impairment after a car crash

Sammanfattning: Background: Road traffic injuries constitute a major public health problem worldwide. Permanent medical impairment (PMI) is used as a measure of seriousness of injuries in Sweden. There is little knowledge on consequences of road traffic injuries in terms of sickness absence (SA), disability pension (DP), and PMI as well as on associations between PMI and DP. Aim: The overall aim of this thesis was to gain knowledge on SA, DP, and PMI among individuals injured in a passenger car crash, in general and in specific groups. Methods and materials: Two exploratory studies using data linked from Swedish nationwide registers were conducted. Study I was a population-based cross-sectional cohort study. It included all individuals living in Sweden, aged 16-64 years, with in- or specialized out-patient healthcare in 2010 due to injury from a new passenger car crash (n=9427). The study investigated already ongoing SA/DP and new SA at the time of the crash. Study II was a prospective cohort study of injured car occupants aged 17-62 years, reported to the Swedish insurance company Folksam Insurance Group during 2001-2013 (n=64,007). The cohort was followed up two years after the crash date regarding SA, DP, and PMI. In both studies, only SA spells >14 days were considered, and descriptive statistics and logistic regressions, to calculate odds ratios (OR) and 95% confidence intervals (CI), were conducted. Results: In Study I, 9% were already on SA or DP at the time of the crash; of the others, 10% had a new SA spell. Injury type was the factor with the highest association with having new SA. Injuries to the spine and spinal cord was the injury type most likely to result in a new SA spell, compared with the reference group: sprain of the cervical spine (ages 16-44; OR: 6.32; CI: 4.42-9.05. Ages 45-64; OR: 17.32; CI: 9.85-30.48). Among the younger (16-44 years), injuries to the lower extremities was the injury type with the second highest OR: 5.64; CI: 4.08-7.81, while among 45-64 year olds, the second highest OR was found for traumatic brain injury of other type than concussion (OR: 14.68; CI: 5.80-37.17). In study II, 13% were already on SA or DP at the time of the crash. At follow-up two years after the crash, 7% among those not already on SA/DP at the time of the crash were on SA and 2% on DP. Furthermore, 8% of the total cohort had a determined PMI. The proportion on DP at follow-up was low among those with no or low PMI, but higher with increasing PMI. Sickness absence status at the time of the crash, and PMI grade were the factors most strongly associated with DP at two years after the crash. The factor most strongly associated with PMI was the model year of the car. The older the car, the higher risk of PMI. Occupants injured in cars with model year ≤1990 were most likely to have a PMI, compared to the reference group with model years 2006-2010 (OR: 3.36; CI: 2.67-4.23). Conclusion: Proportions for which the car crash led to a new SA spell varied greatly with type of injury. Being on DP two years after the crash was highly associated with already being on SA at the time of the crash. Thus, both injury type and prevalent SA are important factors to consider when studying SA and DP after a car crash. Higher grades of PMI were associated with higher DP rates among those injured. These findings indicate that both DP and PMI can be used to measure long-term effects of road traffic injuries.