Chronic Moderate Sleep Restriction in Older Adults

Epidemiologic studies have consistently shown that self -reported sleep durations of <7 hr and >8 hr are associated with increased mortality and morbidity. The risks associated with short sleep are consistent with a vast experimental literature indicating detrimental effects of profound sleep restriction. However, there has been little study of chronic moderate sleep restriction, which is far more common, and thus more important from a public health standpoint. The risks associated with long sleep have scarcely been experimentally examined, though epidemiological data suggest sleep restriction might promote health/longevity in long sleepers. Older adults might be more vulnerable than young adults to negative effects of further sleep impairment, perhaps particularly via inflammatory mechanisms. Negative effects might be at least as evident in long sleepers as in average sleepers if long sleep reflects underlying morbidity, as many have posited. On the other hand, older adults might tolerate (or benefit) from moderate sleep restriction. Older adults often tend to spend excessive time in bed (TIB), particularly long sleepers, and extra TIB could contribute to age-related sleep fragmentation and morbidity, which could be ameliorated with modest TIB restriction. The aims of this study are: (1) to examine the ability of older long sleepers and older average sleepers to adhere to 60 min TIB restriction; and (2) to contrast effects of 12 weeks of 60 min TIB restriction on health-related measures in older long vs. average sleepers. One hundred older adults (ages 60-80 yr) who report sleeping 8-9 hr per night and 100 adults of the same age range who report sleeping 6-7.25 hr per night will be examined at 4 experimental sites over 5 years. Following a 2-week baseline, participants will be randomly assigned to one of two 12-week treatment groups. (1) A sleep restriction group (n=60 long sleepers and n=60 average sleepers) will be assigned to a fixed sleep- wake schedule, in which time in bed is reduced precisely 60 min below each participant's baseline time in bed (TIB). (2) A control group (n=40 long sleepers and n=40 average sleepers) will have no sleep restriction, but will also follow a fixed sleep schedule. Sleep will be assessed continuously with actigraphy and a daily diary. Questionnaires will be answered. Measures will include body weight, glucose tolerance, sleepiness, depression, quality of life, psychomotor vigilance, incidence of automobile accidents, incidence of illness, and multiple markers of inflammation. Physical exams during weeks 2 and 6 of the intervention and a study ombudsman will further monitor potential adverse effects. Follow-up assessments will be conducted for 12 months. The proposed clinical trial will provide the most comprehensive Phase 1 assessment of risks and benefits of chronic moderate TIB restriction ever conducted.

Inclusion criteria

• 60-80 years of age
• Sleeping an average of 8-9 hr per night for long sleeper (or)
• Sleep an average of 6.0-7.25 hr per night for short sleepers
• Able to designate a study partner that can speak on their behalf throughout the course of the study.

Exclusion criteria

• Reported average sleep duration of < 8.0 hr or > 9.0 hr for longer sleepers
• Reported average sleep duration of < 6 hr or > 7.25 hr for the average sleepers
• Spending > 30 min time in bed in the morning and/or night outside of the major sleep period (e.g., watching tv)
• Expected change in usual sleep duration in the near future (e.g., change in work schedule)
• Reported average napping of > 2 naps/day or total nap duration of > 90 min/day;
• Recent shift-work (previous 2 months) or travel across multiple time zones (previous 4 weeks), or plans for performing shift-work or transmeridian travel during the study time period;
• Severe sleep apnea (apnea-hyponea index of greater or equal 15);
• Obesity (body mass index ≥35);
• High daytime sleepiness (Epworth Sleepiness Scale ≥ 10);
• Depression (Quick Inventory of Depressive Sympotomology > or equal to 16);
• Use of hypnotics or other drugs prescribed to promote sleep;
• Alcohol dependence or drug use;
• Any medical, neurologic, or psychiatric illness causing long sleep;
• Factors associated with significant changes in inflammation, including several medical disorders (e.g., rheumatoid arthritis), medications (e.g., steroids) and current smoking;
• Any health or mental condition that would contraindicate participation in the rigors of the study