Doctors, researchers and social scientists have long sought associations between personal health and factors of nature such as weather, season and day of the week. Here’s what we know about health risks and statistics as plotted on the weekly calendar from Monday to Sunday:

Heart attacks and fullbacks

Research shows conclusively that the most common day for heart attacks is Monday. Statistics spike on Monday mornings, in particular, since heart attacks occur between 4 a.m. and 10 a.m. more than any other six-hour period. The Women’s Heart Foundation notes that blood platelets are stickier in the morning hours, which can contribute to an attack.

Incidentally, any day your favorite sports team is playing may represent increased risk as well. A 2002 British study—Admissions for myocardial infarction and World Cup football—concludes that heart attacks “can be triggered by emotional upset, such as watching your football team lose an important match.”

Asked to identify the time of day when most migraine headaches start, subjects in a study by Leslie Kelman, M.D., most commonly answered “anytime.” But the first runner-up was “morning,” which is supported by other studies as well. Reports also suggest that migraines in children are more likely to occur on Mondays. “No scientific reason has been established but presumably it’s [associated with] the stress of returning to school on Monday after a weekend off,” says Dr. Kelman, medical director of the Headache Center of Atlanta and member of the American Headache Society.

Smokers’ stress

Most smokers need to make several attempts before quitting for good, and that first surrender to the stick can happen at any time. “People relapse as a result of stress,” says Patrick Reynolds, executive director of The Foundation For A Smoke-Free America (and grandson of tobacco mogul R.J. Reynolds). “The stress can be positive, such as being out with friends and being overwhelmed by an urge to smoke; or negative, as with the stress induced by work and pressure. But it’s stress either way.” A year-long study in Australia showed that the volume of calls to a smoking quitline peaked between Monday and Wednesday, with around three times as many calls compared to Sunday.

Heart attacks in the hospital

It’s unfortunate that Saturday is the second most common day for heart attacks since survival rates for in-hospital cardiac arrest are lower during nights and weekends. However, the major finding in a 2008 study published in JAMA (Journal of the American Medical Association) is that a patient’s chances are substantially better during daytime hours than at night (specifically, between 11 p.m. and 7 a.m.). Weekday survival rates were better than weekend rates, too, but the disparity was not as significant as the difference between day and night.

Hump-day statistic

In 2009, a study culling five years of U.S. suicide data showed that “the Wednesday effect on suicide was much stronger than for any other day.” Wednesday incidences accounted for a full 24.6 percent of reported suicides. Monday, by contrast, was at only 14.3 percent and came in third (following Saturday). The same study showed that suicides among both men and women were more prevalent in the summer than any other season, controverting earlier research that men were more prone in spring and women in spring or autumn.

Night jitters and patient safety

The Institute of Medicine raised awareness back in 2000 when it stated there are more than 98,000 preventable in-hospital deaths annually. System-wide improvements have been instituted since then, but patient safety remains a major challenge—especially on Saturdays and Sundays. A special report published by the American Medical Association stated that the number of hospital personnel tended to be lower and that hospitals functioned less efficiently between midnight Friday and midnight Sunday. The quality of care in teaching hospitals, or most any hospital that staffs over the weekend with new graduates and less-experienced residents, came under severe scrutiny after the death of Libby Zion in 1984. Zion died a few hours after being admitted to a New York City hospital late on a Sunday night.