Melatonin concentrations are the lowest during the first three months of life and then drastically increase, which could explain why newborn babies wake so often in the night. Levels peak between ages 1-3, then drop progressively throughout childhood by 80%. Changes to the circadian rhythm during adolescence are behind the shift seen in teenagers who suddenly stay up until the wee morning hours and have trouble waking before noon. During adulthood, levels continue to decline, dropping another 10% in later years. Difficulties with sleep are very common in older adults, possibly because of declining levels of hormones, including melatonin.