A 39 Year mortality study of survivors exposed to sulfur mustard agent: A survival analysis

Abstract

Background: The primary objective of this study was to analyze the long-term survival of 48,067 chemical warfare survivors who suffered from pulmonary, cutaneous, and ocular lesions in the decades following the Iran-Iraq war. Methods: The data for this study were obtained from the Veterans and Martyr Affair Foundation (VMAF) database. The survivors were divided into two groups based on whether they were evacuated/admitted (EA) to a hospital or not evacuated/admitted (NEA) to a hospital. The proportional hazard (PH) assumption for age categories, gender, exposure statuses, and eye severity was not satisfied. Therefore, we used a Generalized Gamma (GG) distribution with an Accelerated Failure Time (AFT) model for analysis. Results: The study included a total of 48,067 observations, and among them, 4342 (9.03 %) died during the study period. The mean (SD) age of the survivors was 55.99 (7.9) years. The mortality rate increased with age, and higher rates were observed in males. Survival probabilities differed significantly among age categories, provinces, lung severity, and eye severity based on log-rank tests (p-value<0.05 for all). The GG model results showed that higher age and being male were associated with a shorter time to death. The study also found that the mortality rate was significantly higher in the EA group compared to the NEA group. Conclusion: The present study showed no significant difference in survival time between the EA and NEA groups. The findings suggest that pulmonary lesions caused by mustard gas are more likely to be fatal compared to skin and eye lesions. The results also indicate a potential association between survival time and the severity of lung damage.

Keywords

• Iran-Iraq war
• Sulfur mustard
• Generalized gamma distribution
• Survival time