Stephen F. Smagula is a PhD student in aging epidemiology at the University of Pittsburgh Graduate School of Public Health. His research focuses on the natural history of mood and sleep disturbance among older adults in both community and treatment settings. He is interested in understanding heterogeneity in mood and sleep disturbances as well as their change over time in order to inform both clinical and preventative interventions.
ElderBranch interviewed Mr. Smagula to discuss his recently published article, “Sleep Architecture and Mental Health Among Community-Dwelling Older Men,” which he wrote with Dr. Jane A. Cauley of the University of Pittsburgh Graduate School of Public Health, Dr. Charles F. Reynolds III of the Western Psychiatric Institute and Clinic of UPMC, Dr. Sonia Ancoli-Israel of the University of California San Diego and the VA Center of Excellence for Stress and Mental Health (CESAMH), Dr. Elizabeth Barrett-Connor and Dr. Jan M. Hughes-Austin of the University of California San Diego, Dr. Thuy-Tien Dam of Columbia University, Dr. Misti Paudel of the University of Minnesota, Dr. Susan Redline of Brigham and Young Women’s Hospital, and Dr. Katie L. Stone of the California Pacific Medical Center.
What led you to research the association between mental health and the distribution of sleep stages of older men? Why is this important to understand and examine? How does your current research augment other work in this area?
People with common mental health problems tend more often to have disturbed sleep. Many people have trouble by sleeping too little or too much, or waking up not feeling rested. In addition, sleep is known to be a biologically active process – we and many other researchers believe that the activity of the brain during this time is important to health.
With a device called a polysomnograph (PSG), we can measure the activity of the brain throughout the night. Basically we just measure the electrical activity at the scalp during sleep and this does a good job indicating the activity of our brain while we are asleep. PSG recordings were first conducted more than 50 years ago.
On the basis of these recordings, scientists noted that the activity of the brain cycles through distinct stages during the nights, with a period of about 90 minutes. Typically we enter our nightly slumber through light sleep which progresses into sleep where it is somewhat more difficult to wake us up. The brain next enters what is called slow wave sleep (SWS), or deep sleep. Rapid Eye Movement (REM) sleep is next, and as the name implies, the eyes move rapidly back and forth under the closed eyelid. The exact function of what the brain is doing during these stages remains unknown.
Mental health research dating back to the 1970s tested whether people with depression spent more or less time in any particular phase. Scientists consistently noted that adults with depression spent more time in REM sleep! Although it was eventually recognized that this could not be used as a biological marker to detect depression, the finding was still seen as a help to scientists trying to understand what in the brain is different when people are depressed.
But this previous research was based purely in the laboratory/clinic setting, which means that participants in these studies might be fundamentally different than the general population (on the basis of their selection/being in the clinic for depression).
Recent technological advances have allowed us to make PSG recordings in a residential setting. We made these recordings in about 3,000 older men who lived independently in the community.
In our study we set out to answer the question: Do older adults with depressive and/or anxiety symptoms spend more or less time in any particular sleep stage (when compared to men without these mental health problems)?
Please describe your study. What were your methods?
The Osteoporotic Fractures in Men Study (MrOS) conducted Sleep Studies on 3,135 older men, including PSG. The study also asked participants whether they had been experiencing a list of 15 common depression symptoms (the Geriatric Depression Scale) and whether they had been experiencing 9 common anxiety symptoms (the Goldberg Anxiety Scale). These scales can be used to define a “probable depressive disorder” and “probable anxiety disorder.”
Next we created four groups: men who had probable depression only (DEP+/ANX-), men who had probable anxiety only (DEP-/ANX+), men who had both probably depression and anxiety (DEP+/ANX+), and men who had neither probable depression nor anxiety (DEP-/ANX-).
Then we simply looked at the percentage of sleep time spent in each stage and used statistical tests to compare whether the differences observed were greater than would be expected by chance. We also controlled for relevant confounders in order to make sure that any differences observed were attributable to the effect of the mental health problem observed and not, say, confounders like co-morbid physical health problems or medications that might affect sleep architecture on their own.
What were your key findings?
Contrary to our expectation, we found that men with probable depression only (DEP+/ANX-), compared to men without these mental health problems (DEP-/ANX-), spent a lesser amount of time in REM sleep. Recall that previous research showed that depression was associated with spending more time in REM sleep! Multiple adjustments and sensitivity analyses confirmed our finding of less time spent in REM sleep for participants who had depressed mood.
We also noted that, as expected, men with depressed mood spent a greater percentage of their sleep time in lighter, stage 2 sleep.
What are the implications of your findings?
The take-home message is that for older adults, mood disturbance is at least related to the functional biology of sleep. The associations we observed between depressed mood and sleep architecture mimic what happens with aging: As we age, there is a tendency to spend more time in lighter sleep and less time in REM sleep – just like the men with depressed mood in our study. Therefore depressed mood may be related to an acceleration of age-related changes to sleep architecture.
Mood and sleep problems are also known to increase the risk of other health problems like dementia and heart disease. The more we learn, the more it seems that not only are mood and sleep intimately related, but that mood and sleep are central to successful aging. Although future research is needed to clarify the details, combating depression and maintaining sleep quality can help prevent health declines.
What are the next steps to further your work?
Because our study included only men, it is important to next examine whether these same patterns emerge in similar samples of women. Both mental health and sleep architecture were assessed at the same time, so we haven’t answered the question of what comes first: changes to mood or sleep architecture? Finally future work is needed to determine whether the link between depression and dementia can be explained by differences in sleep architecture.
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