Editing Insomnia (section)

== Prognosis ==
[[File:Insomnia world map - DALY - WHO2004.svg|thumb|upright=1.3|[[Disability-adjusted life year]] for insomnia per 100,000&nbsp;inhabitants in 2004:{{Div col|small=yes|colwidth=10em}}
{{legend|#b3b3b3|no data}}
{{legend|#ffff65|less than 25}}
{{legend|#fff200|25–30.25}}
{{legend|#ffdc00|30.25–36}}
{{legend|#ffc600|36–41.5}}
{{legend|#ffb000|41.5–47}}
{{legend|#ff9a00|47–52.5}}
{{legend|#ff8400|52.5–58}}
{{legend|#ff6e00|58–63.5}}
{{legend|#ff5800|63.5–69}}
{{legend|#ff4200|69–74.5}}
{{legend|#ff2c00|74.5–80}}
{{legend|#cb0000|more than 80}}
{{div col end}}]]

A survey of 1.1 million residents in the United States found that those who reported sleeping about 7 hours per night had the lowest rates of mortality, whereas those who slept for fewer than 6 hours or more than 8 hours had higher mortality rates. Severe insomnia—sleeping less than 3.5 hours in women and 4.5 hours in men—is associated with a 15% increase in mortality, while getting 8.5 or more hours of sleep per night was associated with a 15% higher mortality rate.<ref name="Kripke-2002"/>

With this technique, it is difficult to distinguish the lack of sleep caused by a disorder, which is also a cause of premature death, versus a disorder that causes a lack of sleep, and the lack of sleep causing premature death. Most of the increase in mortality from severe insomnia was discounted after controlling for [[comorbidity|associated disorder]]s. After controlling for sleep duration and insomnia, the use of sleeping pills was also found to be associated with an increased [[mortality rate]].<ref name="Kripke-2002"/>

The lowest mortality was seen in individuals who slept between six and a half and seven and a half hours nightly. Even sleeping only 4.5 hours per night is associated with a very small increase in mortality. Thus, mild to moderate insomnia for most people is associated with increased [[longevity]], and severe insomnia is associated only with a very small effect on mortality.<ref name="Kripke-2002"/> It is unclear why sleeping longer than 7.5 hours is associated with excess mortality.<ref name="Kripke-2002">{{cite journal | vauthors = Kripke DF, Garfinkel L, Wingard DL, Klauber MR, Marler MR | title = Mortality associated with sleep duration and insomnia | journal = Archives of General Psychiatry | volume = 59 | issue = 2 | pages = 131–36 | date = February 2002 | pmid = 11825133 | doi = 10.1001/archpsyc.59.2.131 | doi-access = free }}</ref>