Nicotine disturbs sleep because it is a stimulant. The higher the amount ingested the more difficulty falling asleep and staying asleep. Because nicotine is very fast-acting, the alerting effect begins within seconds of inhaling a cigarette. Thus, smoking close to bedtime will delay sleep onset and increase wakefulness in the first portion of the night. Nicotine is also short-acting and therefore withdrawal effects may occur during the second half of the night, potentially disturbing sleep even further. Nicotine patches which slowly deliver nicotine for many hours may produce sleep disturbance all-night long.
Chronic tobacco smoking has the potential to disturb sleep whether or not nicotine is in the body because of its effects on the airway and lungs. Lung disease due to smoking can result in significant breathing difficulty during sleep and highly fragmented sleep. Fluid retention in the throat associated with smoking can increase the possibility of sleep apnea.