Long-term comparative mortality in hyperthyroid patients treated with radio-iodine, a cohort study in England.

BACKGROUND The focus of this long-term study (entry 1950-1989, follow-up to 1996) on hyperthyroid patients treated with 131I was on all-cause mortality and some specific causes other than cancer. The study was carried out on 7209 patients who were residents of the Midlands area around Birmingham, England. In a total exposure of 105,028 patient-years, 3611 deaths were observed, compared with 3186 deaths expected from age/sex-matched rates in the English life tables. RESULTS Data were reported for observed and expected deaths, and SMR values (standardized mortality ratios to one decimal place) by selected causes of death in combinations with duration, age, and 3 dosage groups of 131I. Exposure data were given only for the dosage groups of 131I, not for the results by age or duration. CONCLUSIONS Comparative mortality was significantly increased for all-cause mortality (but with an SMR of only 1.13), and also for cardiovascular and cerebrovascular deaths, and deaths from fracture. Excess mortality was greatest in the first year after entry, and decreased thereafter. There was no reported increase in cancer mortality.