How strong is the evidence for Circadian Rhythm?

Shift work is the best human model for studying real-world circadian disruption, and the evidence here is unusually consistent: two independent dose-response meta-analyses find shift work increases cardiovascular disease morbidity and mortality, and a more recent meta-analysis of night shift work specifically confirms elevated cardiovascular risk indicators. That evidence is currently rated strong (72/100), built on 9 published studies, including 9 meta-analyses -- enough for real confidence in the effect.