Too Much Sleep?

CARDIOVASCULAR DISEASES

When an epidemiologist begins to mine a mountain of case histories, death certificates and related data, he can be virtually sure to find: 1) evidence tending to confirm well-established theories, and 2) something totally unexpected. That is exactly what happened to Statistician E. Cuyler Hammond when he dug into the records of 352,000 men and 440,000 women enrolled nine years ago in the American Cancer Society's long-range epidemiological study.

As expected, Hammond told a heart-disease symposium at Albany Medical College last week, the death rates after age 40 are higher for both men and women if they smoke cigarettes, if they are overweight, if they have high blood pressure, and if they don't exercise much. This holds true for deaths from both heart attacks and strokes.

What Hammond had not expected to find was that the death rates from heart attacks and strokes were higher for both men and women if they regularly slept more than seven hours a night. Seven seemed to be the ideal number of sleep hours; there were only slightly higher than average death rates for people who got less sleep. But among those who slept eight hours, women under 50 had a 53% above normal death rate from heart attacks, and both men and women under 50 had increases of more than 40% in the death rate from strokes. With nine hours' sleep, both sexes had generally but not consistently higher death rates. With ten hours' sleep, the death rate for women over 70 increased 167%, while for men aged 50 to 59, it increased 286%.

What, if anything, do these figures prove? Said Statistician Hammond cautiously: "I would rather not hazard a guess as to the mechanism underlying this association." Neither Hammond nor physicians reviewing his data can be certain which comes first--the arterial disease, or the tendency to sleep longer than average.

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