Safeguard Your Heart and Metabolic Health by Sleeping in the Dark

For many, the two most dreaded numbers appear on their alarm and the scale. Mornings and maintaining a healthy weight are silent enemies often battled independently, but what if they are connected and your sleeping environment is the villain? Research has cast light on unhealthy nighttime shadows, revealing that exposure to even dim light during sleep can disrupt physiological functions and your body’s natural rhythms, potentially harming your cardiometabolic health.

At Symbios, we understand metabolic health’s superhero role in complete wellness as cardiometabolic concerns, including heart disease and diabetes, rapidly increase, and we urge you to read more and discover practical sleep tips to safeguard your heart and reduce the risk of insulin resistance. Be Symbios Smart and wake up refreshed and healthier every day!

The Link Between Light, Insulin, and Cardiometabolic Health

Your meals are broken down into glucose, a sugar that is your body’s primary energy source. As glucose enters your bloodstream, your pancreas releases insulin to help the glucose enter muscle, fat, and liver cells. These cells can immediately use the glucose as energy or save it for later. The pancreas stops producing insulin when the glucose level in the bloodstream decreases unless outside influences, such as light at night, interfere.

Your body rests more naturally in darkness, engulfed in a comfortable sympathovagal balance between your sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) nervous systems. This delicate balance is upset by an increase in sympathetic activity. As such, nighttime light exposure may trigger a stress-like response in the body, which activates the sympathetic nervous system and is linked to elevated insulin levels, resulting in:

• Increased Nighttime Heart Rate: A higher heart rate means your body works harder than it should during rest, which could elevate stress on the cardiovascular system.
• Decreased Heart Rate Variability (HRV): HRV measures the variation in time between each heartbeat, and a lower HRV indicates that the body is leaning more toward sympathetic (stress) dominance. This imbalance (called higher sympathovagal balance) is a precursor to stress-related disorders.
• Increased Insulin Resistance: Research indicated that those exposed to light during sleep showed impaired insulin sensitivity the following day, which could lead to metabolic dysfunction. The Cleveland Clinic says insulin resistance occurs when cells do not absorb glucose (sugar) efficiently, so the pancreas produces more insulin to compensate. If it can’t keep up, blood sugar levels rise, leading to prediabetes or Type 2 diabetes over time.

How Light-Induced Sleep Disruptions Affect Metabolism  

• Hinder Sleep Quality: Exposure to light at night, whether from indoor or outdoor sources, can lead to shorter sleep, less efficient rest, and more time spent awake after falling asleep. Studieshave proven poor sleep can disrupt metabolism by causing oxidative stress, inflammation, and overproduction of a C-reactive protein. Even without sleep loss, light at night can still reduce sleep quality and increase insulin resistance.
• Interfere with Melatonin Production: Melatonin is produced primarily in the dark, as light acts as the body’s signal to stop melatonin production and wake. Melatonin levels should be high at night, prompting insulin secretion to decrease, which helps regulate blood sugar levels during this fasting period. Melatonin also helps in the recovery of pancreatic β-cells, which produce insulin. Reduced melatonin levels, especially from light exposure at night, can impair this recovery, affecting insulin secretion and glucose regulation.
• Adversely Influence Circadian Rhythm: Light exposure at night can disrupt the body’s internal clock, or circadian rhythm, by lowering melatonin levels. While this hormone regulates the body’s sleep-wake cycle, it also regulates insulin and glucose. When melatonin is suppressed, it can interfere with the recovery of insulin-producing cells, making it harder for the body to manage blood sugar. Additionally, nighttime light can throw off the timing of the circadian system, leading to misalignment between the body’s central clock and metabolic tissues, potentially resulting in insulin resistance and elevated blood sugar levels.
• Overstimulation of the Autonomic Nervous System (ANS): As the ANS controls involuntary body functions, including heart rate, breathing, digestion, and blood pressure, nighttime light exposure can cause it to become overly active. When our ANS expects darkness, light can invoke havoc by stimulating the body’s “fight or flight” response, increasing heart rate and stress hormone levels. This perceived stress causes unrest and imbalance, which contribute to metabolic concerns such as insulin resistance, obesity, and metabolic syndrome.

Tips for a Better Sleep Environment

Keeping your sleep environment as dark as possible can safeguard your heart and metabolic health, giving your body a restful state to regenerate and function optimally. Our modern world is filled with artificial light at night. While we can’t always escape it, talk to your healthcare provider about implementing the following tips to help improve your sleep environment:

• Remove night lights or use a dim blue light
• Silence electronics (enjoy eight hours on Do Not Disturb)
• Avoid screen time before sleep or use a black (night mode) screen
• Install blackout curtains
• Try wearing a light-cancelling sleep mask

At Symbios Heath, your quality of life is our priority! While reducing light at night is one step toward preventing metabolic health issues, we have many more recommendations to elevate your lifestyle. Symbios Health’s in-house laboratory can monitor your glucose levels, and our routine well-checks can set the pace for better long-term health and keep you on the journey toward wellness.