Dysregulation of blood glucose is linked to a large number of serious disorders including heart disease. This study reports a link between shift work and elevated blood glucose levels [possibly a sign of diabetes]. Further work is needed to establish whether this is the norm or just a result of the timing of the testing work.
Evidence from:
Y Suwazono et al. J Occ Env Med (2006) Vol.48 p 455 – 461.
“Long-Term Longitudinal Study on the Relationship Between Alternating Shift Work and the Onset of Diabetes Mellitus in Male Japanese Workers”
A mechanism for harm adds weight to causation arguments.
Further detail: