Hound of the Baskervilles Effect

The Hound of the Baskervilles Effect, also known as the Baskervilles Effect, is the supposed self-fulfilling prophecy that there is an increase in rate of mortality through heart attacks on days considered unlucky because of the psychological stress this causes on superstitious people.

The term derives from the Sherlock Holmes novel 'The Hound of the Baskervilles' in which a hellish-looking dog chases Sir Charles Baskerville, sufferer of a chronic heart disease, and who subsequently dies of a heart attack "with an expression of horror in his face".

The Baskerville Effect was named by David Phillips and his colleagues at the University of California (San Diego, USA) in a paper in which they claimed that the daily number of deaths of Chinese and Japanese Americans from heart attacks between 1973 and 1998 was 7 percent higher on the fourth of the month compared to the average for the other days in that month, while this was not observed in the general American population[1].

Four is considered an unlucky number in Chinese, and hence in the Japanese and Korean, because it sounds like the Chinese word for 'death'. As a result of this superstition, some Chinese and Japanese hotels avoid using it as a room number.

In an analysis of the 20,000 computerized death certificates of Asian-Americans in San Diego, Phillips discovered that there was a 13 percent uptick in death rates on the fourth of the month. The hypothesis was that the peak was caused by stress induced by the superstition surrounding this number.

However, not everyone was convinced about this correlation. In 2002, Gary Smith commented that Phillips and colleagues had omitted data from several heart disease categories, picking only those that happened to have a higher rate on the fourth day, calling them 'chronic heart diseases'. Smith also pointed out that they had not done this on their previous studies of Jewish deaths near Passover and Chinese deaths near the Harvest Moon, where they had used all heart disease categories[2].

Smith also found no statistically relevant peaks on day 4 in data from 1969 to 1988 and 1999 to 2001 for total coronary deaths, inpatients, or the subset of heart diseases used by Phillips and colleagues, adding that there were more deaths on day 5 in the 1969–1988 data, and more deaths on day 3 in the 1999–2001 data.

In 2003, Panesar and colleagues looked for this effect on the Chinese population of Hong Kong. They looked at mortality data from 1995 to 2000, comparing the days of the month with "deathly connotations" (4, 14 and 24) with the other days of the month on both the Lunar and Gregorian calendars, and found no statistically significant difference in the occurrence of cardiac deaths in Cantonese people[3].

[1] Phillips et al: The Hound of the Baskervilles effect: natural experiment on the influence of psychological stress on timing of death in British Medical Journal – 2001. See here.
[2] Smith: Scared to Death? in British Medical Journal – 2002. See here.
[3] Panesar et al: Is four a deadly number for the Chinese? in Medical Journal of Australia – 2003.