Scared to Death?

Gary Smith

Department of Economics

Pomona College

Claremont, California 91711

gsmith@pomona.edu

909.607.3135

Fax 909.621.8576

Phillips, et al, report a “Hound of the Baskervilles effect” among Chinese- and Japanese-Americans who have abnormally high cardiac mortality on the fourth day of the 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 savage dog “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 a comparison of 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 the fourth may show statistical significance that reflects a bulge near the fourth rather than any special significance of the fourth day itself.

California’s computerized mortality records include the racial status recorded on death certificates. The first three data rows of the table show California deaths caused by heart disease during the years 1989-1998 used by Phillips. Of the Chinese- and Japanese-American deaths on days 3, 4, and 5, 33.9% occurred on day 4; the two-sided p value is 0.652. Comparing Chinese/Japanese deaths with white deaths, the two-sided p value is 0.664.

Phillips argues that recorded death dates are more reliable for inpatient data, which have lower p values. The 1989-1998 data use the ninth revision of the International Classification of Diseases (ICD). In his studies of Jewish deaths near Passover² and Chinese deaths near the Harvest Moon Festival,³ Phillips uses all heart-disease categories (390-398, 402, 404-429). In a study of Chinese-Americans with unlucky birth years,⁴ Phillips divides heart diseases into these three groups: (a) 410; (b) 412, 414; and (c) 390-398, 402-409, 411, 413, 415-429. In the Baskervilles paper, Phillips only considers 410-414, which he calls “chronic heart diseases.” These categories have more deaths on day 4 than on days 3 or 5; the categories he omits do not.

One way to check data dredging is to look at fresh data. We now have data for 1999-2001; we also have 1969-1988 data that Phillips has used in his other studies. (Pre-1969 data use ICD-7 classifications that are not directly comparable to the later revisions.) The table shows no statistically persuasive peaks on day 4 for total coronary deaths, inpatients, or Phillips’ subset of heart diseases. In the 1969-1988 data, there are more deaths on day 5 than on day 4; in the 1999-2001 data, there are more deaths on day 3.

Newcombe notes that if day 4 is sufficiently stressful to affect cardiac mortality, it should also affect suicides and accidental deaths.⁵ Phillips’ response (“We were not interested in testing the unsurprising hypothesis that psychological stress might trigger suicide.”) indicates that he agrees. The table shows that Chinese- and Japanese-Americans actually 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, the number 7 can signify death, while white Americans generally consider 7 to be a lucky number; white Americans consider 13 to be unlucky; the luckiest Chinese number is 8. Fisher’s test was applied to cardiac mortality on all days using data for the entire period 1969-2001. None of the suggested days (4, 7, 8, or 13) are statistically persuasive.

Comment

It seems implausible that Chinese- and Japanese-Americans are scared to death by the number 4. California death records do not show statistically persuasive patterns unless several types of cardiac mortality are omitted. The elevated mortality in this pruned subset of the 1989-1998 data is not present in 1969-1988 or 1999-2001 data. Nor are there statistically persuasive patterns in suicides or accidental deaths or on other lucky or unlucky days.

References

1. Phillips DP, Liu GC, Kwok K, Jarvinen JR, Zhang W, Abramson IS. The Hound of the Baskervilles effect: natural experiment on the influence of psychological stress on timing of death. British Medical Journal 2001; 323: 1443-1446.

2. Phillips DP, King EW. Death takes a holiday: Mortality surrounding major social occasions. The Lancet 1988; 2: 728–732.

3. Phillips DP, Smith DG. Postponement of death until symbolically meaningful occasions. JAMA 1990; 263: 1947–51.

4. Phillips DP, Ruth TE, Wagner LM. Psychology and survival, The Lancet 1993; 342: 1142-1145.

5. Newcombe RG. Bad4U? British Medical Journal letters 2002; 324: 1098.

Table Day 4 Deaths as a Percentage of Deaths on Days 3, 4, and 5. The number of deaths on days 3, 4, and 5 and are shown in parentheses.

* Binomial test of the null hypothesis that for each Chinese/Japanese death on the third, fourth, or fifth day of a month, there is a 1/3 probability it occurs on the fourth day.

† Fisher’s exact test with the data separated by race and by whether the death occurred on the fourth day or on the adjacent days.

§ The heart diseases selected by Phillips are ICD-8 410-414; ICD-9 410-414; ICD-10 I20-I24, I25.1-I25.9