There is developing evidence of major individual differences in pathways to different common sleep disorders such as obstructive sleep apnea. Moreover, there is evidence of different clinical presentations of disease and different outcomes. For example, some subjects with obstructive sleep apnea who get excessive sleepiness while others do not. The latter are still at risk for other consequences of the disorder such as cardiovascular disease. These findings indicate that there is a strong scientific rationale for a more personalized approach to diagnosis and management. This applies not only to obstructive sleep apnea but also to other common sleep and circadian disorders.