The stress hormone cortisol is traditionally measured in serum, saliva, and urine, but it is also captured in the hair shaft. Gideon Koren, from The University of Western Ontario (Canada), and colleagues collected hair samples, 3 centimeters long, from 56 adult men who suffered a recent heart attack.  As compared to age-matched healthy counterparts, the team found higher hair cortisol levels corresponding to the previous three months in the heart attack patients. After correcting for confounding variables, the researchers found that hair cortisol content emerged as the strongest predictor of heart attack, concluding that: “This suggests that chronic stress, as assessed by increased hair cortisol in the 3 months prior to the event, may be a contributing factor for [acute myocardial infarction].”