Our hair tells a lot of stories about us. Substances we get in contact with get deposited on our hair and persist there for a long time. Thus, your hair records environmental exposure to substances be it inadvertently (e.g. occupational exposure to certain chemicals) or intentionally (e.g. performance-enhancing and abuse drugs).
In the field of forensic medicine, hair has been invaluable in solving many mysteries and crimes.
A recent study by Israeli researchers indicates that hair can also tell stories about our state of health based on substances our body produce. In particular, the stress hormone cortisol accumulates in our hair and is easy detectable. Thus, our hair actually serves as a “long-term record of chronic stress.” Previous studies on stress relied on interviews, surveys, and questionnaires, with the limitations of relying on people’s long-term memories which are often very subjective. The record on our hair, however, tells a very objective story.
How do the cortisol and other substances get into our hair?
The human hair mainly consists of 3 parts:
- The shaft forms the curls and tresses that are clearly visible on our head. The shaft consists of non-living hair cells.
- The root and bulb of the hair are buried under the skin and contain hair stem cells and dermal papillae. It is supplied by tiny blood vessels in the scalp.
- The follicle is the part that connects the shaft to the root through pores in the skin.
Hair growth is mainly due to production of hair stem cells. Substances in the blood such as cortisol seep into the root and follicle of the hair. These substances get trapped in the growing hair and become part of the shaft. Our hair grows at a rate of about 1 cm per month. Thus, we have several months or years ‘ record of stress based on cortisol levels in our hair. In fact, cortisol has been found to persist in the hair for a long time, from 6 months to 1,500 years in the case of well-preserved Peruvian mummies.
Chronic stress being closely linked to cardiovascular problems, it is logical to hypothesize that high levels of cortisol in the hair are also associated with cardiac events.
The researchers tested this hypothesis by collecting hair samples from 120 patients of the cardiac unit of the Meir Medical Center in Israel. Half of the patients had heart attack, the other half had other diagnoses. The researchers analyzed hair samples for cortisol, mainly the part of the shaft 3 cm closest to the scalp, representing cortisol record of the last 3 months. They found that cortisol levels were significantly higher in men who had heart attacks compared to those without.
The results need to be confirmed by larger studies before the technique becomes mainstream for testing heart attack, but it has the following advantages:
- It is non-invasive.
- It is more reliable than long-term memories of stress.
- It is not expensive.