Journal
CHRONOBIOLOGY INTERNATIONAL
Volume 22, Issue 4, Pages 695-709Publisher
TAYLOR & FRANCIS INC
DOI: 10.1080/07420520500180439
Keywords
aging; circadian rhythm; melatonin; aMT6s; cortisol; sleep
Categories
Funding
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R56HL071123, R01HL071123] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE ON AGING [R01AG012364, R01AG015763] Funding Source: NIH RePORTER
- NHLBI NIH HHS [HL071123] Funding Source: Medline
- NIA NIH HHS [AG15763, AG12364] Funding Source: Medline
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There is evidence that aging may impair phase-shifting responses to light synchronizers, which could lead to disturbed or malsynchronized circadian rhythms. To explore this hypothesis, 62 elder participants (age, 58 to 84 years) and 25 young adults (age, 19 to 40 years) were studied, first with baseline 1-wk wrist actigraphy at home and then by 72 h in-laboratory, studs, using an ultra-short sleep-wake cycle. Subjects were awake for 60 Minutes in 50 lux followed by 30 minutes of darkness for sleep. Saliva samples were collected for melatonin, and urine samples were collected for aMT6s (a urinary metabolite of melatonin) and free cortisol every 90 minutes. Oral temperatures were also measured every 90 minutes. The timing of the circadian rhythms was not significantly more variable among the elders. The times of lights-out and wake-up at home and urinary free cortisol occurred earlier among elders, but the acrophases (cosinor analysis-derived peak time) of the circadian rhythm of salivary melatonin, urinary aMT6s, and oral temperature were not significantly phase-advanced among elders. The estimated duration of melatonin secretion was 9.9 h among elders and 8.4 h among young adults (P < 0.025), though the estimated half-life of blood melatonin was shorter among elders (P < 0.025), and young adults had higher saliva melatonin and urinary aMT6s levels. In summary, there was no evidence for circadian desynchronization associated with aging, but there was evidence of sonic rearrangement of the internal phase-angles among the studied circadian rhythms.
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