How Much Sleep Do You Really Need? Why It Matters for Health and Longevity

Cassie Wellock PA-C
Aug 20, 2025
8 min read

Sleep is one of the most powerful tools we have for restoring health, protecting the brain, and promoting longevity—yet it’s often the first thing sacrificed in our busy lives. While nutrition and exercise get plenty of attention, sleep is the foundation that allows both to work at their best.

How Much Sleep Do You Need?

The National Sleep Foundation and American Academy of Sleep Medicine recommend:

Adults (18–64 years): 7–9 hours per night
Older adults (65+ years): 7–8 hours per night
Teenagers: 8–10 hours per night
Children: 9–12 hours per night

While some individuals claim to function well on less, long-term studies show that consistently getting fewer than 6–7 hours increases risk for chronic diseases, early mortality, and cognitive decline (Walker, 2017; Cappuccio et al., 2010).

Why Sleep Is Critical

Cellular Repair and Growth: Deep sleep (slow-wave sleep) triggers growth hormone release, which supports tissue repair, muscle recovery, and immune function.
1. Deep sleep—also called slow-wave sleep (SWS)—is the stage when the body focuses most on healing, repair, and regeneration. During this phase, the brain produces slow, synchronized electrical waves, the body is least responsive to outside stimuli, and some of the most important biological recovery processes occur.
2. Growth Hormone and Tissue Repair- One of the defining features of slow-wave sleep is the release of growth hormone (GH) from the pituitary gland. Growth hormone plays a crucial role in:
  1. Muscle repair and recovery: GH stimulates protein synthesis, helping repair microtears from exercise or daily activity.
  2. Bone health: It promotes bone remodeling and density, supporting long-term skeletal strength.
  3. Skin and connective tissue repair: Collagen production is enhanced during deep sleep, aiding in wound healing and skin elasticity.
3. Immune Function- Sleep is also when the immune system strengthens its defenses. During slow-wave sleep, the body produces and releases cytokines—proteins that help fight infection and inflammation. Sleep deprivation has been shown to:
  1. Reduce production of natural killer (NK) cells, which are essential for fighting viral infections and even targeting cancer cells.
Brain Health: During sleep, the brain’s glymphatic system clears amyloid-beta and other proteins linked to Alzheimer’s disease (Xie et al., 2013).
1. One of the most fascinating discoveries in sleep research over the last decade is the role of the glymphatic system—a clearance pathway in the brain that functions primarily while we sleep. Much like the lymphatic system in the body, the glymphatic system helps remove metabolic waste products from brain cells, but it relies on cerebrospinal fluid (CSF) moving through channels around blood vessels to flush out toxins. This process helps clear amyloid-beta and tau proteins, both of which are strongly associated with Alzheimer’s disease when they accumulate and form plaques or tangles (Xie et al., 2013).
  1. Research shows that:
    1. Poor or fragmented sleep increases amyloid-beta deposition. One study using PET scans found that just a single night of sleep deprivation increased amyloid-beta accumulation in the hippocampus and thalamus—regions essential for memory (Shokri-Kojori et al., 2018).
    2. Chronic short sleep duration is linked to higher Alzheimer’s risk. Longitudinal studies suggest people who consistently sleep fewer than 6 hours per night have a significantly higher likelihood of developing dementia (Sabia et al., 2021).
    3. Quality matters as much as quantity. Slow-wave (deep) sleep appears most critical for amyloid clearance. People with fragmented sleep or sleep disorders, such as sleep apnea, often have reduced slow-wave sleep and thus impaired glymphatic function.
    4. This makes sleep not just restorative in the short term, but also a neuroprotective process for the long term. By promoting glymphatic clearance, high-quality sleep may delay or even reduce the risk of neurodegenerative diseases like Alzheimer’s and Parkinson’s.
Metabolic Health: Lack of sleep disrupts insulin sensitivity, increasing the risk of type 2 diabetes and obesity.
1. Even partial sleep restriction has effects. In one landmark study, healthy young men restricted to just 4–5 hours of sleep for a week showed a 30–40% reduction in insulin sensitivity, making their metabolic profiles resemble those of prediabetes (Spiegel et al., 1999).
2. Sleep loss alters hunger hormones. Short sleep raises ghrelin (hunger hormone) and lowers leptin (satiety hormone), which leads to increased appetite—especially for high-carb, high-calorie foods (Taheri et al., 2004).
3. Cortisol and nighttime eating. Poor sleep elevates evening cortisol, the stress hormone that promotes fat storage, particularly around the abdomen. Combined with increased cravings, this creates a metabolic “perfect storm” for weight gain.
4. Chronic risk. Meta-analyses show that people who regularly sleep fewer than 6 hours per night have a significantly higher risk of developing type 2 diabetes and obesity compared to those who get 7–8 hours (Cappuccio et al., 2010).
Cardiovascular Protection: Poor sleep increases blood pressure, systemic inflammation, and cardiovascular risk.
1. The heart and blood vessels rely on sleep to reset and repair. When sleep is cut short or fragmented, the cardiovascular system stays in a state of overdrive, increasing stress on arteries and the heart itself. Over time, this contributes to hypertension, systemic inflammation, atherosclerosis, and higher risk of stroke and heart disease.
2. During deep sleep, blood pressure naturally falls by about 10–20%—a phenomenon called “nocturnal dipping.” This nightly drop gives the heart and vascular system a chance to rest. In people with sleep deprivation or sleep disorders (like sleep apnea), this dip is blunted or absent, leaving blood pressure elevated around the clock. Chronic high nighttime blood pressure is a well-documented risk factor for heart attacks and strokes (Bilo et al., 2020).
3. Poor sleep also activates the body’s inflammatory pathways. Studies show that short sleep duration raises levels of C-reactive protein (CRP) and interleukin-6 (IL-6)—biomarkers strongly associated with cardiovascular disease. In addition, insufficient sleep impairs the function of the endothelium, the inner lining of blood vessels, making arteries stiffer and more prone to plaque buildup (Sauvet et al., 2010).
4. Sleep problems can also disrupt the heart’s electrical system. For example, sleep apnea is linked to a higher risk of atrial fibrillation, a common heart rhythm disturbance.
5. Epidemiological studies consistently show that people who sleep fewer than 6 hours per night have a 20–48% higher risk of developing or dying from coronary heart disease compared with those who sleep 7–8 hours (Cappuccio et al., 2011). On the flip side, consistently prioritizing quality sleep helps regulate blood pressure, reduces inflammation, and promotes vascular health—key pillars of cardiovascular longevity.

Conditions That Can Disrupt Sleep

Insomnia and poor-quality sleep can arise from multiple conditions, including:

Sleep apnea – interrupted breathing during sleep leading to low oxygen and frequent awakenings.
Restless leg syndrome – uncomfortable sensations in the legs that disrupt rest.
Chronic pain syndromes – arthritis, fibromyalgia, or neuropathy.
Psychiatric conditions – anxiety, depression, and PTSD.
Endocrine disorders – hyperthyroidism, menopause, or adrenal dysfunction.
Neurological conditions – Parkinson’s disease, dementia.

Evidence-Based Treatments for Sleep Problems

Treatment depends on the root cause, but peer-reviewed research highlights several effective strategies:

Cognitive Behavioral Therapy for Insomnia (CBT-I): First-line treatment shown to be more effective long-term than medications (Trauer et al., 2015).
Sleep hygiene:
1. Core Components of a Sleep Hygiene Protocol
  1. Consistent Sleep and Wake Times- Going to bed and waking up at the same time every day—even on weekends—helps regulate the circadian rhythm, making it easier to fall asleep and wake naturally.
  2. Optimizing the Sleep Environment- Cool, dark, and quiet: The ideal bedroom temperature is about 65–68°F. Blackout curtains, white noise machines, or earplugs may help.
  3. Comfortable bedding: A supportive mattress and pillows reduce nighttime awakenings.
  4. Technology-free zone: Blue light from phones and TVs suppresses melatonin, delaying sleep onset.
2. Light Exposure and Circadian Rhythm
  1. Morning light: Getting natural sunlight within an hour of waking reinforces circadian rhythms.
  2. Evening light restriction: Dim lights and avoid screens 1–2 hours before bed to allow melatonin production.
3. Nutrition and Substances
  1. Limit caffeine: Avoid coffee, tea, or energy drinks at least 6–8 hours before bed.
  2. Avoid heavy meals and alcohol before sleep: Both disrupt deep sleep cycles.
  3. Hydration balance: Too much fluid right before bed can cause awakenings to urinate.
4. Pre-Sleep Routine
  1. Establish calming rituals: reading, gentle stretching, meditation, journaling, or herbal teas like chamomile.
  2. Keep the last 30–60 minutes of the day screen-free and focused on relaxation.
5. Physical Activity
  1. Regular exercise improves sleep depth and duration, but avoid vigorous workouts within 2–3 hours of bedtime, as they may increase alertness.
6. Mental Conditioning
  1. Reserve the bed for sleep and intimacy only—avoid working, scrolling, or eating in bed. This trains the brain to associate the bedroom with rest.
  2. If unable to fall asleep within 20 minutes, get up, do a quiet activity in dim light, then return to bed once sleepy.
Treatment of underlying conditions: CPAP for sleep apnea, iron supplementation for restless legs (if ferritin is low), therapy for anxiety/depression.
Medication (when necessary): Short-term use of prescriptions medications may be necessary for significant issues with sleep, under medical supervision.

Supplements That May Support Sleep

While not a substitute for addressing root causes, some supplements have scientific support:

Magnesium (glycinate or threonate): Supports GABA activity and relaxation; low magnesium is linked to poor sleep quality (Abbasi et al., 2012).
L-theanine: Found in green tea, promotes relaxation and reduces sleep latency.
Glycine: Shown to improve sleep quality and decrease time to fall asleep.
Valerian root extract: Some studies suggest mild benefits, though results are mixed.
Chamomile: Can reduce anxiety and calm the nervous system while improving sleep quality.

The Bottom Line

Sleep is not optional—it’s essential for long-term health, brain protection, and longevity. Chronic sleep deprivation accelerates aging, while consistent, high-quality sleep is linked to lower disease risk and longer lifespan. If you’re struggling with sleep, addressing lifestyle factors, and ruling out medical conditions can help restore balance.

References

Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M. M., Hedayati, M., & Rashidkhani, B. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences, 17(12), 1161–1169.
Bilo, G., Grillo, A., Guida, V., & Parati, G. (2020). Morning blood pressure surge: Pathophysiology, clinical relevance and therapeutic aspects. Integrated Blood Pressure Control, 13, 71–81.
Cappuccio, F. P., D’Elia, L., Strazzullo, P., & Miller, M. A. (2010). Quantity and quality of sleep and incidence of type 2 diabetes: A systematic review and meta-analysis. Diabetes Care, 33(2), 414–420.
Cappuccio, F. P., Cooper, D., D’Elia, L., Strazzullo, P., & Miller, M. A. (2011). Sleep duration predicts cardiovascular outcomes: A systematic review and meta-analysis of prospective studies. European Heart Journal, 32(12), 1484–1492.
Chang, S. M., & Chen, C. H. (2016). Effects of an intervention with drinking chamomile tea on sleep quality and depression in sleep-disturbed postnatal women: A randomized controlled trial. Journal of Advanced Nursing, 72(2), 306–315.
Redline, S., Yenokyan, G., Gottlieb, D. J., Shahar, E., O’Connor, G. T., Resnick, H. E., ... & Punjabi, N. M. (2010). Obstructive sleep apnea–hypopnea and incident stroke: The Sleep Heart Health Study. American Journal of Respiratory and Critical Care Medicine, 182(2), 269–277.
Sabia, S., Fayosse, A., Dumurgier, J., van Hees, V. T., Paquet, C., Sommerlad, A., ... & Singh-Manoux, A. (2021). Association of sleep duration in middle and old age with incidence of dementia. Nature Communications, 12, 2289.
Sauvet, F., Leftheriotis, G., Gomez-Merino, D., Langrume, C., Drogou, C., Van Beers, P., ... & Chennaoui, M. (2010). Effect of acute sleep deprivation on vascular function in healthy subjects. Journal of Applied Physiology, 108(1), 68–75.
Shokri-Kojori, E., Wang, G. J., Wiers, C. E., Demiral, Ş. B., Guo, M., Kim, S. W., ... & Volkow, N. D. (2018). β-Amyloid accumulation in the human brain after one night of sleep deprivation. Proceedings of the National Academy of Sciences, 115(17), 4483–4488.
Spiegel, K., Leproult, R., & Van Cauter, E. (1999). Impact of sleep debt on metabolic and endocrine function. The Lancet, 354(9188), 1435–1439.
Spiegel, K., Sheridan, J. F., & Van Cauter, E. (2002). Effect of sleep deprivation on response to immunization. JAMA, 288(12), 1471–1472.
Srivastava, J. K., Shankar, E., & Gupta, S. (2010). Chamomile: A herbal medicine of the past with bright future. Molecular Medicine Reports, 3(6), 895–901.
Taheri, S., Lin, L., Austin, D., Young, T., & Mignot, E. (2004). Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Medicine, 1(3), e62.
Trauer, J. M., Qian, M. Y., Doyle, J. S., Rajaratnam, S. M., & Cunnington, D. (2015). Cognitive behavioral therapy for chronic insomnia: A systematic review and meta-analysis. Annals of Internal Medicine, 163(3), 191–204.
Walker, M. (2017). Why We Sleep: Unlocking the Power of Sleep and Dreams. Scribner.
Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., ... & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373–377.
Zick, S. M., Wright, B. D., Sen, A., & Arnedt, J. T. (2011). Preliminary examination of the efficacy and safety of a standardized chamomile extract for chronic primary insomnia: A randomized placebo-controlled trial. BMC Complementary and Alternative Medicine, 11, 78.