"The association with CHD depends on the severity of vertex baldness and also exists among younger men," wrote Tomohide Yamada, MD, of the University of Tokyo, and colleagues.
American Heart Association (AHA) spokesperson Nieca Goldberg, MD, a cardiologist at New York University, said that the reason for the link between vertex baldness and CHD is unclear.
While the mechanism is being worked out, physicians can still act, Goldberg said. "If a patient comes in with male pattern baldness and hasn't been screened for CHD risk factors, it is time to do that," said Goldberg, who was not involved with the work.
For the study, the Japanese researchers combed the Medline and the Cochrane Library databases for research published on male pattern baldness and CHD. They found 850 studies, published between 1950 and 2012.
Three cohort studies and three case-control studies met all the eligibility criteria and were included in the analysis. All had been published between 1993 and 2008, and involved 36,990 men.
Among the findings:
- Men with severe baldness were 32% more likely to develop CHD than men who retained a full head of hair (P = 0.008). When the analysis was confined to younger men (aged 60 or younger), a similar association emerged.
- In the three case-control studies, the adjusted relative risk for baldness was 1.70 for all participants (P = 0.03) and 1.84 for younger men (P = 0.0001).
- Three studies assessed the degree of baldness using the modified Hamilton scale. Analysis of these results showed that only vertex baldness was significantly associated with CHD and the link was dependent on the severity of baldness.
- Extensive vertex baldness boosted the risk by 48% (P = 0.03), moderate vertex baldness by 36% (P 0.001), and mild vertex baldness by 18% (P 0.001). In contrast, there was no significnt assoiation between frontal baldness and CHD (P = 0.28).
To compensate for differences in the methods of assessing baldness in the studies, the authors performed a sensitivity analysis that used personal scales to classify baldness: none; frontal; crown-top; or combined. The results were similar.
The big question is how losing hair on the top of the head is associated with heart disease.
"It has been suggested that classical coronary risk factors (e.g. age, hypertension, dyslipidemia and smoking) might influence both conditions, so that baldness is a marker of atherosclerosis.
"It has also been postulated that baldness is linked to CHD by mechanisms such as hyperinsulinemia, chronic inflammation and increased peripheral sensitivity to androgen," the authors wrote.
Goldberg said all those theories are worth pursuing. Still, it could turn out that baldness is just a sign of aging, she said.
The analysis from researchers in Japan follows by less than a week a case-control study that linked early onset baldness in African-American men to increased risk of prostate cancer.
Even while the reasons for the association between vertex baldness and CHD are worked out, Goldberg said it's better safe than sorry: Screen previously untested men who present with vertex baldness for CHD risk factors. Tell us what you think by using the Add Your Knowledge link below. -- Sanjay Gupta, MD.
The authors and Goldberg had no relevant disclosures.
Reference: Yamada T, et al "Male pattern baldness and its association with coronary heart disease: a meta-analysis" BMJ Open 2013; DOI: 10.1136/bmjopen-2012-002537.