A prospective study of S-T segment depression in the electrocardiogram and mortality in the population

A prospective study was carried out of all degrees of horizontal or descending depression of the S-T segment in the electrocardiogram (more than 1 mm or 0.1 mV, 0.5-0.9 mm or 0.05-0.05 mV and up to 0.5 mm or 0.05 mV) in a sample of 2414 subjects of both sexes, aged 35-54 years, (1326 females and 1088 males) in six Croatian regions on three occasions during a 13-year period: 1969, 1972 and 1982, according to the Minnesota code. S-T segment depression in the ECG was found during the first examination in 10.69% of females and 4.13% of males; during the second examination in 12.66% females and 6.24% males, and in the third examination in 19.06% females and 12.12% males. S-T segment depression of up to 0.5 mm was dominant and twice as frequent in females than in males, and the difference was significant. S-T segment in the ECG was also analyzed in a sample of 239 subjects (141 males and 98 females) who died during the period between the second and third examination, and for whom ECGs had been recorded in 1969 and 1972. In the group of females who died during the period between the first and second examination, 16.32% had all degrees of S-T segment depression, while in the group of surviving females this amounted to 10.6%. In the group of deceased males this finding was found in 4.24% of deceased and 4.13% of surviving males. In the group of females who died between the second and third examination, S-T segment depression was found in 18.36% of deceased and 12.66% of surviving females, and 10.62% in deceased males and 6.24% in surviving males (depression of 1 mm or deeper and 0.5-0.9 mm was found in 7.08% of deceased and 1.28% surviving males). The relative risk of mortality in middle-aged females with S-T segment depression of 0.5 mm or deeper, was 3.65 times higher than in females without such ECG changes, while the relative risk of mortality in males of the same age with the same finding was 5.85 times higher than in those without such ECG changes.