BY TRACY McCUBBIN, MD, ABOIM, ABEM
One sheep, two sheep, the spreadsheet that I need to complete…
The American Psychological Association estimate that 50 million Americans suffer from some kind of sleep disorder. Less than 50% of Americans get the recommended 7-8 hours of sleep each night. Many of those that achieve 8 hours require sleep aids to get that precious sleep. There are many reasons that sleep eludes us. Insomnia is one of the constant complaints that I see in my patients. And it contributes to many of the medical issues they face.
The Science Behind Sleep
An internal “body clock” regulates your sleep cycle, controlling when you feel tired or alert. This clock operates on a 24-hour cycle known as circadian rhythm. In 2017, three American researchers won the Nobel Prize in Medicine for discovering what makes us tick – the molecular circuitry of the body clocks that control our life on Earth.
Their work, done over decades, helps explain how life adapts to the 24-hour cycle of the day and also how diseases like cancer arise. This has resulted in countless research initiatives like those around sleep!
The drive to sleep may be linked to adenosine, an organic compound produced in the brain. Adenosine levels increase throughout the day and the body breaks down this compound during sleep.
Light also influences circadian rhythm. A part of the brain called the hypothalamus contains a cluster of cells which process signals when the eyes are exposed to light. These signals help the brain determine if it is night or day.
As natural light disappears in the evening, we release melatonin, a hormone that causes drowsiness. When the sun rises in the morning, we release cortisol hormone which promotes energy and alertness. These hormone levels can be tested and balanced as needed!
What are the Stages of Sleep?
Once we fall asleep, our bodies follow a sleep cycle which is divided into four stages.
Each has significance and importance. These stages repeat cyclically through the night. For most people the duration of each cycle will last about 90-120 minutes.
Stage 1: This first stage marks the transition between wakefulness and sleep and consists of light sleep. It lasts several minutes. Muscles relax, heart rate, breathing and brain waves begin to slow down.
Stage 2: The aforementioned bodily functions continue to slow down and temperature begins to decrease. This is a deeper stage of sleep and lasts the longest of the 4 sleep stages.
Stage 3: This stage plays an important role in making you feel refreshed and alert the next day. Heartbeat, breathing and brain wave activity slow to their lowest levels. This stage will be longer at first and decrease in duration throughout the night.
Stage 4: Rapid Eye Movement (REM). This is the sleep associated with dreaming and memory consolidation. Heart rate speeds up, breathing is irregular and the brain is highly active compared with other stages. The first REM stage occurs about 90 minutes after you fall asleep. The duration of each REM sleep cycle increases as the night progresses. However, the duration of REM sleep decreases as we age.
Why is Our Sleep Disrupted?
Perimenopause, for example, disrupts sleep patterns. The low progesterone during this period delays sleep onset and shortens sleep periods. As estrogen declines, night sweats cause nighttime awakening. For my male patients, benign prostatic hypertrophy (BPH) and nocturia can present a problem. When stress is present and the mind starts cycling, getting back to sleep can be next to impossible. Daily life is stressful and it is our sleep that suffers.
Children and pets can interrupt sleep. Or a snoring significant other! Obstructive sleep apnea involves cessation or significant decrease in airflow in the presence of breathing effort. It is characterized by recurrent episodes of upper airway collapse during sleep. These episodes are associated with low oxygen and arousals from sleep. Despite being a common disease, sleep apnea is underrecognized by most primary care physicians in the United States; an estimated 80% of Americans are not diagnosed.
Sleep apnea is a very important diagnosis for physicians to consider because of its strong association with and potential cause of the most debilitating medical conditions, including hypertension, cardiovascular disease, coronary artery disease, insulin-resistance, diabetes and depression.
Consequences of Insomnia
What are the consequences of this sleep deficit? Previous studies from the medical literature have shown that sleep flushes toxic molecules and waste from the brain. A recent study from the scientific journal Nature shows that sleep protects us from atherosclerosis aka “hardening of the arteries.” Interrupted sleep led to higher numbers of monocytes in the blood and larger plaques in the arteries (3). A monocyte is a white blood cell (WBC). Multiple studies link higher numbers of circulating WBC to the development of atherosclerosis. This can lead to heart attacks and strokes.
Another team demonstrated in mice that sleep depletes levels of amyloid-beta and tau – 2 proteins that are linked to Alzheimer disease (AD). This finding was corroborated in human cerebrospinal fluid (fluid around the brain and spinal column). Death of brain cells was slowed down in mice who had uninterrupted sleep.
Most recently researchers found that people over the age of 50 who get less than 6 hours of sleep on a regular basis are more likely to develop dementia.
Take home message: Inadequate or fragmented sleep can predispose people to atherosclerosis and Alzheimer Disease. So, get your ZZZ’s to protect both your brain and your heart.
If you feel like lack of sleep is affecting your health, give us a shout. We would love to help!
Sweet dreams,
Dr. Tracy