All areas of medicine are focused on developing a personalized approach to diagnosis and treatment of specific conditions. This is based on the fundamental concept that all subjects with apparently the same disorder are different. There are multiple reasons for these differences. These include differences in the sequence of DNA, differences in the environment, differences in epigenetics, some of which may be driven by environmental differences and differences in the microbiome. These different factors will result in variations in multiple aspects of the phenotype. This includes different pathways to disease, different symptoms, different pattern of comorbidities and risk for adverse outcomes, and different physiological changes during sleep as a result of breathing episodes.