Balding men may have a greater risk of heart disease because they have higher levels of the male hormone testosterone than men with a full head of hair, according to a US study.
The research involved more than 22,000 "hair-impaired" male physicians aged from 40 to 84 who were enrolled in the Physicians' Health Study. The research was carried out by a team from Harvard Medical School and Brigham and Women's Hospital in Boston.
The researchers found a strong relationship between male pattern baldness and coronary heart disease over an 11-year period. The relative risk was associated with the particular type of baldness that developed, according to the study.
Compared to men with no hair loss, men whose crowns were completely bald had a 36 per cent greater risk of having a coronary event, such as a heart attack, angina, or heart surgery including angioplasty or bypass surgery.
Those with frontal baldness had a 9 per cent greater risk of heart disease than men with full heads of hair, men with mild balding of the crown were at 23 per cent higher risk and men with moderate crown balding had a 32 per cent greater risk.
The study found several potential explanations for the link between baldness and heart disease. One theory focuses on elevated levels of androgens, male hormones that include the sex hormone testosterone.
Bald men seem to have a greater number of androgen receptors in their scalps and androgens may contribute to both atherosclerosis, a build-up of fatty deposits in the arteries, and thrombosis, a susceptibility to blood clots.
In addition, both heart disease and baldness may be traits that are inherited together, the study said.
Not much is known about the genetics of hair loss, but researchers said bald men could be monitored more closely for heart problems.
"Although early vertex baldness may be a non-modifiable risk factor for CHD [coronary heart disease], it may serve as a useful clinical marker to identify men at increased risk who may benefit from aggressive screening and primary prevention efforts," study author Dr Paulo Lotufo wrote in the Archives of Internal Medicine.
The association between male pattern baldness and heart disease has been identified by at least three previous studies, Dr Lotufo said.