As if losing your hair was not enough, a new study has found that male pattern baldness may be linked to an increased risk of coronary heart disease (CHD), but only if it is at the top of the head.

A receding hairline does not appear to increase the risk.

Japanese researchers looked at all published research on male pattern baldness and CHD that was published between 1950 and 2012. Out of a possible 850 studies, six studies, involving almost 40,000 men, were selected and assessed. All were published between 1993 and 2008.

Three of the studies followed the progress of men for at least 11 years. Among these studies, the researchers found that those who had lost most of their hair were 32% more likely to develop CHD than their peers who still had a full head of hair.

Furthermore, when the analysis was confined to men under the age of 60 only, this figure rose to 44%.

Among the other three studies, balding men were 70% more likely to have CHD, while younger balding men were 84% more likely to have it.

Meanwhile half of the studies found that the risk of CHD depended on the severity of the baldness, but only if this was on the top of the head. Men who had mild baldness on the top of their head had a 18% increased risk of CHD, while those with extensive baldness here had a 48% increased risk.

According to the researchers from the University of Tokyo, there could be a number of reasons for these findings, for example, baldness may suggest insulin resistance, which is a precursor to diabetes. People with diabetes are known to have an increased risk of heart disease.

Bald people may also have increased sensitivity to testosterone, which is also linked to heart disease.

"Our findings suggest that vertex (top of the head) baldness is more closely associated with systemic atherosclerosis (hardening of the arteries) than with frontal baldness. Thus, cardiovascular risk factors should be reviewed carefully in men with vertex baldness, especially younger men, who should probably be encouraged to improve their cardiovascular risk profile," the team said.

Details of these findings are published in the journal, BMJ Open.

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