"Men find doing things relaxing, and that in itself is good for their health."Europe’s Men Need Their own Health Strategy, BMJ, 29 November 2011
What are men doing in sheds?
The Telegraph says they're banging nails, welding metal, shaping wood, and disassembling/reassembling cars.
The Daily Mail says they're doing crossword puzzles.
Maybe women have already found their sheds?
"At any given age, men are still more likely than women to die from most of the leading causes, and in the European Union men have more than twice as many deaths a year as women throughout the working ages (15-64 years)."