It is accepted in some jurisdictions that there are negative impacts on crew health (both pilot and cabin)
In these jurisdictions there is no requirement to PROVE causal link between disease (be it some forms of tissue and blood illness) and the employment; it is accepted.
Companies in these jurisdictions compensate for illness and indeed recognise the impact of circadian rhythm disturbance. Shift workers including pilots have worse health outcomes.
Mix in jet lag and the results are likely worse..
Ever wonder why Little Napoleon wants "science" on proving flights (with a sample size n=3) ??
If pilots and cabin crew ever worked together collectively QF and other airlines would be very exposed to litigation...