Male pattern baldness is linked to an increased risk of coronary heart disease, but only if it`s on the top/crown of the head, a new study has revealed.

A receding hairline is not linked to an increased risk, the analysis indicates.

The researchers from University of Tokyo trawled the Medline and the Cochrane Library databases for research published on male pattern baldness and coronary heart disease, and came up with 850 possible studies, published between 1950 and 2012.

But only six satisfied all the eligibility criteria and so were included in the analysis. All had been published between 1993 and 2008, and involved just under 40,000 men.

Three of the studies were cohort studies - meaning that the health of balding men was tracked for at least 11 years.

Analysis of the findings from these showed that men who had lost most of their hair were a third more likely (32 percent) to develop coronary artery disease than their peers who retained a full head of hair.

When the analysis was confined to men under the age of 55-60, a similar pattern emerged. Bald or extensively balding men were 44 percent more likely to develop coronary artery disease.

Analysis of the other three studies, which compared the heart health of those who were bald / balding with those who were not, painted a similar picture.

It showed that balding men were 70 percent more likely to have heart disease and those in younger age groups were 84 percent more likely to do so.

Three studies assessed the degree of baldness using a validated scale (Hamilton scale). Analysis of these results indicated that the risk of coronary artery disease depended on baldness severity, but only if this was on the top/crown of the head, known as the vertex.

Extensive vertex baldness boosted the risk by 48 percent, moderate vertex baldness by 36 percent, and mild vertex baldness by 18 percent. By contrast, a receding hairline made very little difference to risk, the analysis showed.

The study is published in the online journal BMJ Open.