Impact of Chronic Circadian Disruption vs. Chronic Sleep Restriction on Metabolism

It has long been recognized that sleep patterns change with age. A common feature of aging is
the advance of the timing of sleep to earlier hours, often earlier than desired. These
age-related changes are found in even healthy individuals who are not taking medications and
who are free from sleep disorders. In addition to these sleep disturbances, many older
individuals curtail their sleep voluntarily, reporting similar rates of sleep restriction
(sleeping less than 7 or less than 6 hours per night) when compared to young adults. Whether
voluntary or not, insufficient sleep has medical, safety and metabolic consequences. In fact,
converging evidence in young adults suggests that sleep restriction per se may impair
metabolism, and that reduced sleep duration is associated with weight gain, obesity,
diabetes, cardiovascular disease, and mortality. An understanding of how the circadian and
sleep homeostatic neurobiological processes responds to increasing homeostatic sleep
pressure, and the effects of sleep restriction on metabolism at different ages, should
provide information on the regulation of sleep and metabolism in aging, as well as direction
for future treatments. In the present study, we will study the separate impacts of chronic
sleep restriction (while minimizing circadian disruption) and chronic circadian disruption
(while minimizing sleep disruption) and a poor diet on metabolism.

Inclusion Criteria:

- Healthy adults with conventional and regular sleep-wake timing

- Non-smokers

- Completion of medical, psychological, and sleep screening tests

- Able to spend 37 consecutive days/nights in the laboratory

Exclusion Criteria:

- History of neurological or psychiatric disorder

- History of sleep disorder or regular use of sleep-promoting medication

- Current prescription, herbal, or over-the-counter medication use

- Traveling across 2 or more time zones within past 3 months

- Donating blood within past 8 weeks

- Worked night or rotating shift work within past 3 years

- Hearing impairment

- Drug or alcohol dependency