Sleep - we spend about a third our lives doing it, we're the only mammal that willingly delays it, yet when it's disturbed, it can lead to a number of chronic illnesses including dementia, cancer, diabetes, heart disease and obesity. Sleep deprivation can also mess with your immune system, has been linked to metabolic diseases like obesity and type 2 diabetes, and is implicated in Alzheimer's disease and many mental health problems including depression. Recent research on sleep has uncovered...