PROBLEM: 30 to 40 percent of adult men have male pattern baldness. Some research has suggested that there's an association between hair loss and heart disease, but not enough to consider it as a possible early warning sign.
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METHODOLOGY: After evaluating the merits of the existing literature -- over 850 studies published since 1950 -- Japanese researchers narrowed the field to six sufficiently rigorous studies that together account for almost 40,000 men. Three were cohort studies, following the health of balding men over time; the other three, case-control studies, compared bald men to peers with full heads of hair. All controlled for complicating factors like age and smoking.
RESULTS: Across the board, increased balding was strongly linked to increased risk of CHD.
Mostly-bald men in the cohort studies were 32 percent more likely to develop CHD over the follow-up period than those who weren't balding. Under the age of 55-60 (the studies grouped them differently), the association remained and was even intensified: CHD risk for the "extensively balding" was upped to 44 percent.
In the cohort studies, bald and balding men were as high as 70 percent more likely to have heart disease than non-balding peers. In the younger age groups, their risk was increased by 84 percent.
Risk was concentrated on the top of the head. Two studies, taken together, showed that as this area became mildly, moderately, and extensively more sparse, the odds of a participant developing heart disease escalated from 18, to 36, to 48 percent, respectively.
Receding hairlines, in the above case, were not significantly correlated with CHD. And overall, front-of-head baldness was associated with increased heart disease to a much lesser degree than other balding patterns.
IMPLICATIONS: The leading theory, which the authors say their analysis supports, is that hair loss from the top of the head is one of the more visible symptoms of hardened arteries; a condition caused by unhealthy behaviors that in turn causes heart disease. Insulin resistance, chronic inflammation, and increased sensitivity to testosterone are also linked to both conditions.
Does this mean that hair loss can be added to the list of early warning signs of heart disease -- just like high cholesterol, family history, smoking, and obesity, to name a few -- that doctors should look out for in their patients? Well, these researchers seem to think this could be a good idea -- once further study elucidates the risk and clarifies screening guidelines. After all, male baldness is extremely common; as the authors admit, medicating everyone who's thinning out on top would likely create more problems than it would solve.
"Male pattern baldness and its association with coronary heart disease: a meta-analysis," is published in BMJ Open.