Nearly half of adult men are losing their hair.

They could be losing their hearts too.

A new study links baldness to an increased risk of heart disease.

The study, published in the medical journal BMJ Open, reviewed more than 850 studies dating back to the 1950's.

Where you're balding is important.

Thinning at the crown indicates an increased risk of heart disease by at least one-third.

For those with both frontal and crown-top baldness, risk was increased by nearly 70%.

Only have receding at the hair line? You're in the clear, no increased heart disease risk -- at least from hair evidence.

Severity of hair loss also matters: the more hair lost, the higher the heart disease risk.

Baldness is genetic. It's also hormone-related, which may explain the link between baldness and an ailing heart. Hormone-related mechanisms include insulin resistance, which can lead to diabetes -- a known heart disease risk factor -- and inflammation, also known to accelerate atherosclerosis (plaque build-up in heart arteries).

Bald men are likely more sensitive to testosterone, which could also increase atherosclerosis.

Talk to your doctor about screening for heart disease risk factors.