Long-term whiplash-associated disorders, sickness absence, and disability pension following rear-end car crashes and associations with whiplash protection systems: a longitudinal cohort study.

BACKGROUND: Whiplash-associated disorders (WAD) are common injuries from car crashes, with a significant proportion leading to permanent medical impairment (PMI), especially among women and in rear-end impacts. While previous research has shown mixed results regarding work incapacity following WAD, severe cases may lead to long-term health and functional consequences. This study aimed to examine the occurrence of long-term WAD – based on insurance compensation, future PMI, and work incapacity (sickness absence (SA) and disability pension (DP)) among front seat occupants in rear-end crashes, and to assess how seat design with or without whiplash protection systems (WPS) relates to these outcomes. METHODS: The cohort (N = 14,363) was selected from car crashes occurring 2001–2013, reported to the Folksam Insurance Group. Injury- and car-related information was linked with nationwide register data regarding sociodemographics, inpatient and specialized outpatient healthcare, SA, and DP. The SA + DP days/year were calculated in relation to the crash date. Logistic regression analyses were performed with variables combining WPS and car model year of introduction (< 1998 and ≥ 1998) for long-term WAD, PMI, and > 90 days of all diagnoses and whiplash-specific SA/DP in year two after the crash. Analyses were stratified by sex. RESULTS: Among women, 18% sustained long-term WAD and 12% resulted in PMI. Among men,13% and 9%, respectively. Among occupants with long-term WAD, there was a substantial increase in mean SA/DP days/year, WAD specific and all diagnoses, after the crash and remained high three years after. Compared to occupants in cars with WPS, occupants in older cars (< 1998) without WPS were more likely to have long-term WAD (Women: OR:1.8, 95% confidence intervals (CI):1.5–2.2; Men: OR:2.2, 95% CI:1.7–2.8), and PMI (Women: OR:1.4, 95% CI:1.1–1.8; Men: OR:2.3, 95% CI:1.6–3.3). Among men, also occupants in newer cars without WPS were more likely to have long-term WAD (OR:1.6; 95% CI:1.2-2.0) and PMI (OR:1.9; 95% CI;1.3–2.7). Among men, but not women, those injured in older cars without WPS were more likely to have > 90 days SA/DP in year two following the crash (OR:1.8; 95% CI: 1.2–2.6). CONCLUSION: WPS were associated with a lower risk of long-term WAD, PMI, and prolonged SA/DP, particularly among men, with substantial less benefit for women. These sex differences highlight the need to improve WPS performance, especially for women.