Sleep and immunity in older age

The general decline in sleep duration during the past 25 years has made suboptimal sleep quality a more common phenomenon (Jean-Louis et al., Biol Psychiatry 47:921-927, 2000). Reasons for reduced sleep include increased working hours, shift work and more time spent watching the television and exploring the internet (Bonnet and Arand, Sleep 18:908-911, 1995). Disruptions in sleep parameters have been related to a variety of health outcomes. Animal studies have shown that extreme levels of sleep deprivation are highly detrimental. Rats subjected to total sleep deprivation for up to 21 days displayed global deterioration ultimately resulting in death (Everson and Wehr, Am J Physiol 264:R376-R387, 1993). Epidemiological studies in humans have indicated that both short- and long-sleep duration is associated with increased morbidity and mortality. Most notably, a study of 1.1 million participants in the American Cancer Prevention Society demonstrated that survival was optimal in people who slept 7 h per night. Sleep durations of 8.5 h or more, or less than 4.5 h were significantly associated with increased mortality as well as higher body mass index (BMI) scores (Kripke et al., Arch Gen Psychiatry 59:131-136, 2002).