Scared to death?BMJ 2002; 325 doi: http://dx.doi.org/10.1136/bmj.325.7378.1442 (Published 21 December 2002) Cite this as: BMJ 2002;325:1442
- Gary Smith, Fletcher Jones professor ()
Phillips et al report a “Hound of the Baskervilles effect” among Chinese-Americans andJapanese-Americans, who have abnormally high cardiac mortality on the fourth day of each month because they think the number 4 is unlucky.1 Is it plausible that the number 4 is regarded with the same terror that the fictional Charles Baskerville felt as he was pursued in the dark by a huge hound “with its flaming jaws and blazing eyes”? We encounter the number 4 every day. Could one more 4, the fourth day of a month, be fatal?
Methods and results
A natural test is to compare deaths on the third, fourth, and fifth days of each month. A longer horizon is flawed because a systematic cycle that causes deaths to peak near day 4 may show statistical significance that reflects a bulge near the day rather than any special importance of day 4 itself.
California's computerised mortality records include the racial status recorded on death certificates. The first section of the table shows deaths in California caused by heartdisease during 1989-98—the data used by Phillips. Of the Chinese-American and Japanese-American deaths on days 3, 4, and 5, 34% occurred on day 4 (P=0.652). Our comparison of deaths of Chinese and Japanese people with deaths of white people produced a P value of 0.664.
Phillips et al argued that recorded death dates were more reliable for inpatient data, which have lower P values. Their 1989-98 data were classified according to ICD-9 (international classification of diseases, ninth revision). In their studies of Jewish deaths near Passover2 and Chinese deaths near the Harvest Moon Festival,3 Phillips and colleagues used all heart disease categories (390-398, 402, 404-429). In a study of Chinese-Americans with unlucky birth years,4 Phillips et al divided heart diseases into three groups: 410; 412 and 414; and 390-398, 402-409, 411, 413, and 415-429. In the Baskervilles paper, however, Phillips et al considered only categories 410-414, which they called “chronic heart diseases.” These categories have more deaths on day 4 than on days 3 or 5, whereas the categories they omitted do not.
We now have data for 1999-2001; we also have the 1969-88 data that Phillips used in his other studies. (Pre-1969 data are classified by ICD-7 and are not directly comparable with later revisions.) The table shows no statistically persuasive peaks on day 4 for total coronary deaths, inpatients, or Phillips et al's subset of heart diseases. In the 1969-88 data there were more deaths on day 5 than on day 4; in the 1999-2001 data there were more deaths on day 3.
Newcombe noted that, if day 4 is sufficiently stressful to affect cardiac mortality, it should also affect suicides and accidental deaths.5 Our table shows that Chinese and Japanese people had relatively few suicides on day 4, which casts doubt on the theory that day 4 is fatally stressful.
If the number 4 affected mortality, we should find similar effects with other lucky and unlucky numbers. In Chinese culture number 7 can signify death, whereas white Americans generally consider 7 to be lucky; white Americans consider 13 to be unlucky, while the luckiest Chinese number is 8. We applied Fisher's test to cardiac mortality on all these days, using data for the period 1969-2001. None of the suggested days (4, 7, 8, or 13) was statistically persuasive.
It seems implausible that Chinese-Americans and Japanese-Americans are scared to death by the number 4. Californian death records do not show statistically persuasive patterns unless several types of cardiac mortality are omitted. The higher mortality in this pruned subset of the 1989-98 data is not present in 1969-88 or 1999-2001 data, nor are there statistically persuasive patterns in suicides or accidental deaths or on other lucky or unlucky days.
Christmas competition: see p 1498
Competing interests None declared.