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

Older cars without WPS were linked to higher long-term WAD and PMI, especially in men. 2. WPS offer more protection to men than women in rear-end collisions. 3. Long-term WAD leads to sustained increases in sickness absence and disability days. 4. Newer cars without WPS still show increased risk for men. 5. Improved WPS design is needed to better protect women in crashes. 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. 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. 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). 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.