Sleep medicine deals with the causes, diagnosis and treatment of sleep disorders. A sleep medicine physician treats problems such as sleep apnea and snoring, insomnia and narcolepsy. Sleep apnea is when a person actually stops breathing for a few seconds during sleep, and is usually accompanied by loud snoring. Narcolepsy is a disorder of the central nervous system, and is characterized by excessive daytime sleepiness, and a tendency to sleep at inappropriate times, even if the person gets adequate nighttime sleep. Also considered sleep disorders are periodic limb movements and restless legs.

Treatment includes overnight study in a sleep center, where technicians observe, monitor, and analyze brain activity, respiratory function, muscle function and other variables that help diagnose complex sleep disorders. Sometimes a physician may fit a patient may with a device to measure a person's activity, their environmental temperature, light levels and mood state, all recorded by a computer the size of wrist watch. This allows the physician to get objective, accurate data on the patient's daily life, and help to assess sleep problems.

Doctor density varies by specialty and location. California has 140 practicing sleep medicine doctors. Broken out by city, sleep medicine doctor density in Anaheim is 4, in Arcadia is 2, in Auburn is 1, in Azusa is 1, in Bakersfield is 1, in Barstow is 1, in Berkeley is 1, in Beverly Hills is 1, in Burbank is 1, in Burlingame is 1, in Carlsbad is 1, in Carmichael is 1, in Castro Valley is 1, in Chino is 1, in Clovis is 1, in Colton is 1, in Concord is 1, in Corona is 1, in Covina is 1, in Cupertino is 3, in Duarte is 1, in Encinitas is 1, in Encino is 1, in Folsom is 1, in Fort Bragg is 1, in Fountain Valley is 1, in Freedom is 3, in Fremont is 2, in Fresno is 3, in Fullerton is 2, in Glendale is 4, in Greenbrae is 1, in Gridley is 1, in Hanford is 1, in Harbor City is 1, in Hayward is 1, in Huntington Beach is 2, in Irvine is 1, in Irwindale is 1, in La Jolla is 1, in La Mesa is 1, in La Palma is 1, in Laguna Beach is 1, in Laguna Hills is 1, in Lodi is 1, in Loma Linda is 1, in Long Beach is 8, in Los Angeles is 16, in Madera is 1, in Menlo Park is 1, in Mission Viejo is 2, in Modesto is 1, in Monterey is 2, in Moreno Valley is 1, in Murrieta is 1, in Newport Beach is 1, in North Hollywood is 2, in Oakland is 2, in Orange is 4, in Oxnard is 1, in Palm Springs is 1, in Palo Alto is 15, in Pasadena is 6, in Pleasanton is 1, in Pomona is 2, in Rancho Cucamonga is 1, in Redlands is 1, in Riverside is 1, in Roseville is 3, in Sacramento is 3, in Salinas is 3, in San Clemente is 1, in San Diego is 6, in San Francisco is 8, in San Jose is 1, in San Leandro is 1, in San Marcos is 1, in San Ramon is 2, in Santa Ana is 3, in Santa Barbara is 2, in Santa Cruz is 4, in Santa Maria is 2, in Santa Monica is 5, in Sherman Oaks is 1, in Signal Hill is 1, in Simi Valley is 1, in South Lake Tahoe is 1, in Stanford is 9, in Stockton is 3, in Sunnyvale is 2, in Tarzana is 1, in Thousand Oaks is 1, in Torrance is 3, in Travis Afb is 1, in Tulare is 1, in Upland is 1, in Vista is 1, in Walnut Creek is 4, in Watsonville is 2, and in Whittie is 1.

California’s population is 36,142,137, and it is America’s third largest and most populous state. It also claims the highest and lowest altitudes in the lower 48 states. The lowest point in the country, Death Valley, is also home to the nation’s highest recorded temperature, 134 degrees. Tourists flock to this state for its many outdoor activities and attractions, including Universal Studios, Disneyland, Rodeo Drive shopping, the Golden Gate Bridge in San Francisco, wine country tours, and California’s numerous beaches and parks. Los Angeles is the nation’s second largest city, but California’s capital is Sacramento. The giant sequoias in California’s forests are among the oldest living things in the world, and a redwood in the Redwood National Park is said to be the world’s tallest tree, at 365 feet. California achieved statehood in 1850, and was named the Golden State after the beginning of the Gold Rush in 1848.

According to 2005 Census estimates, California has a population of 36,132,147. Of this population, 9,308,563 are under the age of 18 and 3,827,038 are at or above the age of 65.