Abstract
Objective: To determine whether cardiac mortality is abnormally high on days considered unlucky.
Design: The study group consisted of Chinese and Japanese (who consider the number "four" unlucky) and white controls (who do not). Cardiac and non-cardiac mortality on and around the fourth of each month was examined for each group.
Setting: Entire United States.
Subjects: All U.S. Chinese and Japanese (n=209,908) and whites (n=47,328,762) whose computerized death certificates were recorded between 1/1/1973 to 12/31/1998.
Main outcome measures: Ratio of observed number of deaths on day 4 to expected number of deaths on day 4; the expected number was estimated from mortality on other days of the month.
Results: Chinese and Japanese cardiac mortality peaks on the fourth of the month. The fourth-day peak is particularly large for deaths from chronic heart disease (13% above expected; 95% confidence interval, 6%-21%) and still larger for chronic heart deaths in California (27% above expected; 15%-39%). Within this group, inpatients display a particularly large, 47%, fourth-day peak (19%-81%). The fourth-day peak is not followed by a compensatory drop in deaths below normal. White controls, matched on age, sex, marital status, hospital status, location, and cause of death, display no fourth-day peak in cardiac mortality.
Conclusions: Chinese and Japanese cardiac mortality is significantly higher on the fourth than on any other day of the month. The results are inconsistent with nine alternative explanations for the findings. For example, the fourth-day peak does not seem to occur because of changes in the patient's diet, alcohol intake, exercise, or medication regimes. Our findings are consistent with the hypothesis that cardiac mortality increases on psychologically stressful occasions.
