The number of Americans suffering from heart attack peaks in mid-winter and reaches its annual low in July. Researchers say this trend occurs across various climactic regions and may be unrelated to seasonal fluctuations in temperature. There were 53% more cases of heart attack reported during the winter months than in the summer. Many experts have attributed seasonal fluctuations in cardiac events to the added physical strain of dealing with mounting snowdrifts and plunging temperatures. But the same fluctuations in heart attack rates occurred both in the Northeast and the Southwest, where it's not cold and there's no snow to shovel. Sunlight may also play a crucial role. It is well known that light has an influence on a number of physiologic variables, and increased exposure to sunlight may be protective against coronary disease.

Journal of the American College of Cardiology (1998;31:1226-1233)

COMMENT: I find these studies blend quite nicely. I believe that the relative lack of photons that most of us experience during the winter months has a huge impact on our health. I fully believe that as time goes on we will document this better and more fully appreciate the enormous impact that light has on our health.