What are the greatest health risks for pilots?

 poor nutrition and exercise, jet lag, exposure to lots of dry air and occasional non-ionizing radiation, and general quality-of-life complaints & the pilot must lean forward at least a bit. Designers can't just tilt the seat back forward; that's make it impossible to lean back and take a break when the other pilot is flying, or just while sitting in the cockpit on the ground waiting for somebody

Altitude, lack of proper sleep.