Impact of the first Gulf war on multiple sclerosis risk in Kuwait: a quasi-experimental study

OBJECTIVE: It has been reasoned that stressful life events tend to alter immune function thereby increasing the susceptibility to autoimmune diseases including multiple sclerosis (MS). Using the database of Kuwait National MS Registry, this quasi-experimental study assessed the impact of the first Gulf War (Iraqi invasion of Kuwait in 1990) on MS risk in Kuwait. METHODS: MS incidence data from 1980 to 2019 were obtained from the Kuwait National MS Registry. Annual age-standardized incidence rates (ASIRs) (per 10(5) person-years) were computed using the World Standard Population as a reference. Interrupted time series analysis with the option of autoregressive order (1) was used to evaluate the impact of the first Gulf War on MS risk by treating 1990 as an intervention year. RESULTS: Estimated baseline annual ASIR (per 10(5) person-years) was 0.38 (95% CI: -1.02, 1.78; p = 0.587). MS ASIRs (per 10(5) person-years) tended to increase significantly every year prior to 1990 by 0.45 (ASIR per 10(5) person-years = 0.45; 95% CI: 0.15, 0.76; p = 0.005). During the first year of the first Gulf War, there seemed to be a non-significant increase (step change) in ASIRs (per 10(5) person-years) of MS (ASIR per 10(5) person-years = 0.85; 95% CI: − 5.16, 6.86; p = 0.775) followed by a non-significant increase in the annual trend in MS ASIRs per 10(5) person-years (relative to the preintervention trend i.e., the difference between the pre-first Gulf War versus the post-first Gulf War trends) by 0.65 (ASIR per 10(5) person-years = 0.65; 95% CI: − 0.22, 1.52; p = 0.138). However, a postestimation measure of the post-first Gulf War trend was statistically significant (ASIR per 10(5) person-years = 1.10; 95% CI: 0.40, 1.80; p = 0.003), which implies that the post-first Gulf War trend in the annual ASIRs (per 10(5) person-years) inclined to be the same as was the pre-first Gulf War (i.e., counterfactual of the pre-first Gulf War trend in annual ASIRs (per 10(5) person-years) as if no first Gulf War took place).The Durbin-Watson test statistic (d = 1.89) showed almost non-significant autocorrelations across the time series observations on ASIRs (per 10(5) person-years). CONCLUSIONS: This study suggests that the first Gulf War was not significantly associated with the increasing trend in MS risk at population level in Kuwait neither with any short-term change nor with secular trend. Future studies may consider confirming the role of conflict-related stress or other stressful life events in potential exacerbation of MS risk along with unraveling biologically plausible mechanistic pathways.