Toxic oil syndrome mortality: the first 13 years

Background The toxic oil syndrome (TOS) epidemic that occurred in Spain in the spring of 1981 caused approximately 20 000 cases of a new illness. Overall mortality and mortality by cause in this cohort through 1994 are described for the first time in this report. Methods We contacted, via mail or telephone, almost every living member of the cohort and family members of those who were known to have died in order to identify all deaths from 1 May 1981 through 31 December 1994. Cause of death data were collected from death certificates and underlying causes of death were coded using the International Classification of Diseases, 9th Revision. Results We identified 1663 deaths between 1 May 1981 and 31 December 1994 among 19 754 TOS cohort members, for a crude mortality rate of 8.4%. Mortality was highest during 1981, with a standardized mortality ratio (SMR) of 4.92 (95% confidence interval [CI] : 4.39-5.50) compared with the Spanish population as a whole. The highest SMR, (20.41, 95% Cl : 15.97-25.71) was seen among women aged 20-39 years during the period from 1 May 1981 through 31 December 1982. Women <40 years old, who were affected by TOS, were at greater risk for death in most time periods than their unaffected peers, while older women and men were not. Over the follow-up period, mortality of the cohort was less than expected when compared with mortality of the general Spanish population, or with mortality of the population of the 14 provinces where the epidemic occurred. We also found that, except for deaths attributed to external causes including TOS and deaths due to pulmonary hypertension, all causes of death were decreased in TOS patients compared to the Spanish population. The most frequent underlying causes of death were TOS, 350 (21.1%); circulatory disorders, 536 (32.3%); and malignancies, 310 (18.7%). Conclusions We conclude that while on average people affected by toxic oil syndrome are not at greater risk for death over the 13-year study period than any of the comparison groups, women <40 years old were at greater risk of death.