“Christmas coronary” is a term coined by doctors who noticed a disturbing pattern: heart attacks and heart-related problems peaking every year over the winter holiday season — specifically on Christmas, the day after Christmas and New Year’s Day.

In fact, studies show that the number of heart attacks increases across ages and genders by more than 30 percent in the winter, but why? Some of it can be attributed to factors you can fight or control, like these six holiday stressors: