Several media reports picked up on an article in Cancer Epidemiology reporting an association between early onset of baldness and a reduced risk of prostate cancer in later life.

Not surprisingly, this gave rise to some dramatic headlines, such as "Baldness could be good for your health".  Fortunately, there are several useful summaries of this research, linked below.

One key point to make is that the study was a retrospective case-control study.  What this means was that the researchers found a group of men with prostate cancer (cases), then looked back in time to see how many of them went bald early in life. 

The researchers then compared their baldness rate with a group of men who were similar except for the fact that they didn't have prostate cancer (controls).

This type of study cannot prove cause, only an association.  The researchers suggest that this could be to do with the shared hormonal causes of baldness and prostate cancer. It's important to note, however, that other studies have found the opposite association.

There are other methodological limitations too, such as relying on patients' memory to establish baldness patterns 40 years in the past.

This story is a great example of why we need more systematic reviews!

Get the details:

• NHS Choices' Behind the Headlines analysis (note:  there is an error in this article at the time of writing, notified via the comments facility at the foot of the page)
  
• The Prostate Cancer Charity's commentary
• Read the abstract in Cancer Epidemiology journal
• More information about causes of prostate cancer and research into causes of prostate cancer.