Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. However, in a subset of cases sleep deprivation can, paradoxically, lead to increased energy and alertness and enhanced mood; it has even been used as a treatment for depression (see below). Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction. Complete absence of sleep over long periods has not been seen in humans (unless they suffer from fatal familial insomnia); it appears that brief microsleeps cannot be avoided. Long-term total sleep deprivation has caused death in lab animals.

Physiological effects

Generally, sleep deprivation may result in:

The All Nighter is a night bus service network in the San Francisco Bay Area, California. Portions of the service shadow the rapid transit and commuter rail services of BART and Caltrain, which are the major rail services between San Francisco, the East Bay, the Peninsula, and San Jose. BART and Caltrain do not operate owl service so that track maintenance can be performed; the All Nighter network helps fill this service gap. The slogan is, "Now transit stays up as late as you do!"

History

The service launched initially in December 2005, and fully launched in March 2006. BART and Caltrain riders who previously faced uncoordinated substitute bus transit service after midnight can now take advantage of the coordinated All Nighter bus service.

The service is operated by AC Transit, Muni, SamTrans, and VTA. The agencies have a network of timed transfers, and half-hourly weekend service was implemented between downtown San Francisco and several BART stations along the Richmond and Fremont lines. AC Transit Route 800 operates along Market Street in San Francisco; this is the first AC Transit route to operate anywhere within San Francisco beyond the Transbay Terminal.