Health Benefits of Better Sleep and How to Improve It
Most people know they should sleep more. Fewer realise just how much poor sleep affects the body, from immune function and heart health to cognitive performance and long-term disease risk.
The good news is that relatively small changes to your habits can make a measurable difference. This guide covers why sleep matters more than you might think, how much you actually need, and practical steps you can take tonight.
Key Takeaway
Adults sleeping fewer than 6 hours are over 4 times more likely to catch a cold (Prather et al., 2015). Poor sleep also impairs cognitive performance to a level comparable to alcohol intoxication, increases cardiovascular risk, disrupts appetite hormones, and may accelerate Alzheimer's-related brain changes. Consistent sleep habits, bedroom optimisation and evidence-backed supplements offer the most effective improvements.
How Sleep Affects Your Body
Immune Function
During sleep your body produces cytokines, proteins that help fight infection and reduce inflammation. Sleep also gives T cells, the white blood cells that attack invading pathogens, time to regenerate.
A study published in Sleep (Prather et al., 2015) found that adults sleeping fewer than six hours per night were 4.2 times more likely to develop a cold after viral exposure than those sleeping seven hours or more (DOI: 10.5665/sleep.4968). During cold and flu season especially, cutting sleep short leaves you significantly more vulnerable to illness.
Brain Health and Cognitive Performance
Sleep is when your brain consolidates memories, processes new information and strengthens neural connections. Deep sleep in particular is critical for transferring short-term memories into long-term storage.
Without adequate sleep, your ability to concentrate, learn and make decisions declines measurably. Research by Williamson and Feyer (2000) found that after 17-19 hours without sleep, cognitive performance was equivalent to or worse than a blood alcohol concentration of 0.05% (DOI: 10.1136/oem.57.10.649).
There is also growing evidence linking chronic poor sleep to Alzheimer's disease. A landmark study published in Science (Xie et al., 2013) showed that the brain's glymphatic system clears beta-amyloid protein 60% more efficiently during sleep than during waking hours (DOI: 10.1126/science.1241224). Beta-amyloid is the waste product that accumulates into plaques associated with neurodegeneration.
Mental Health and Mood
Your brain needs to cycle through all stages of sleep, including REM sleep, to process the emotions and experiences of the day. When REM sleep is cut short, the result is often increased irritability, heightened anxiety and lower resilience to stress.
Chronic sleep deprivation is strongly associated with depression, and the relationship works both ways. Poor sleep worsens mood, and low mood disrupts sleep. Addressing sleep problems can be one of the most effective first steps in improving overall mental wellbeing.
Heart Health
Insufficient sleep is linked to higher blood pressure, increased inflammation and a greater risk of cardiovascular disease, coronary heart disease and stroke.
Sleep apnoea, a condition where breathing repeatedly stops and starts during the night, is a particularly significant risk factor. If your sleep partner notices uneven breathing patterns or pauses while you sleep, it is worth discussing with your GP.
Weight and Metabolism
Poor sleep disrupts the hormones that regulate appetite. Specifically, it raises ghrelin (which signals hunger) and lowers leptin (which signals fullness), leading you to eat more than your body needs.
Sleep deprivation also reduces motivation to exercise and impairs blood sugar regulation. Over time, chronic poor sleep is associated with weight gain and an increased risk of type 2 diabetes.
How Much Sleep Do You Actually Need?
The NHS recommends that most adults aim for seven to nine hours of sleep per night. However, the quality of that sleep matters as much as the quantity.
| Age Group | Recommended Hours |
|---|---|
| Newborns (0-3 months) | 14-17 hours |
| Infants (4-11 months) | 12-15 hours |
| Toddlers (1-2 years) | 11-14 hours |
| Children (3-5 years) | 10-13 hours |
| Children (6-13 years) | 9-11 hours |
| Teenagers (14-17 years) | 8-10 hours |
| Adults (18-64 years) | 7-9 hours |
| Older adults (65+) | 7-8 hours |
Waking frequently, spending too little time in deep sleep, or sleeping at inconsistent times can all reduce the restorative value of the hours you spend in bed.
Signs that you are not getting enough quality sleep include difficulty concentrating during the day, relying on caffeine to stay alert, feeling irritable without obvious cause, and catching colds or infections more frequently than usual.
Practical Ways to Sleep Better
Watch Your Caffeine Timing
Caffeine has a half-life of roughly six hours. That means half the caffeine from your afternoon coffee is still circulating in your system at bedtime.
If you find it hard to fall asleep, try cutting off caffeine by early afternoon. This includes tea, energy drinks and cola, not just coffee.
Limit Screens Before Bed
Phones, tablets and laptops emit blue light that suppresses melatonin production, the hormone that signals to your body that it is time to sleep.
Equally important, scrolling through social media or watching stimulating content keeps your brain active when it should be winding down. Aim to put screens away at least 30 minutes before bed.
Exercise Earlier in the Day
Regular physical activity is one of the most effective ways to improve sleep quality. However, vigorous exercise within two to three hours of bedtime can have the opposite effect, raising your heart rate and core temperature when your body needs to be cooling down.
Morning or early evening exercise tends to work best for sleep.
Optimise Your Bedroom
A few environmental factors make a surprising difference. Keep the room cool (around 16 to 18 degrees Celsius is ideal for most people), as dark as possible, and quiet.
If your mattress is more than seven to ten years old or you wake up with aches, it may be worth replacing. A supportive mattress is one of the simplest investments in better sleep.
Build a Consistent Routine
Your brain responds to consistent signals. Going to bed and waking up at roughly the same time each day, even on weekends, helps regulate your circadian rhythm.
A short pre-sleep routine such as reading, gentle stretching or writing down any worries in a journal can help your mind transition from the alertness of the day to a state ready for sleep.
Supplements That May Support Sleep
If good sleep habits alone are not enough, certain supplements have clinical evidence behind them for supporting sleep quality.
Strongest Evidence for Natural Sleep Support
A 2024 randomised trial found that 250mg of magnesium bisglycinate taken before bed significantly improved deep sleep, sleep efficiency and heart rate variability over 8 weeks (DOI: 10.2147/NSS.S524348). Ashwagandha KSM-66 reduced cortisol levels by 27.9% in a separate 60-day trial (Chandrasekhar et al., 2012, DOI: 10.4103/0253-7176.106022).
Magnesium glycinate (bisglycinate) is one of the most evidence-backed options for sleep. It helps activate the parasympathetic nervous system, your body's "rest and digest" mode. The glycine it is bonded to has its own calming properties, making this form particularly well suited to evening use. For detailed dosage guidance, see our magnesium glycinate dosage guide.
Ashwagandha KSM-66 is an adaptogenic herb that helps reduce cortisol levels and supports both stress management and sleep onset. It is particularly useful if your sleep problems are driven by stress or an overactive mind at bedtime. For more detail on how ashwagandha works, see our ashwagandha benefits and evidence guide.
Other natural options include melatonin (which helps reset your circadian rhythm, particularly after jet lag or shift work), L-theanine, valerian root and chamomile.
For a more detailed breakdown of each option, see our guide to the best supplements for sleep.
Support Your Sleep Naturally
Magnesium glycinate for relaxation, ashwagandha KSM-66 for stress-driven sleep issues
When to See Your GP
If you have been struggling with sleep for more than a few weeks despite making lifestyle changes, it is worth speaking to your doctor. Persistent insomnia, excessive daytime sleepiness, or restless legs that prevent you from settling at night all benefit from medical assessment.
Sleep problems can also be a symptom of underlying issues such as thyroid disorders, anxiety or depression.
When Sleep Problems Need Medical Attention
Sleep apnoea symptoms: Loud snoring with pauses in breathing, choking or gasping during sleep should be evaluated by a GP as this is a serious cardiovascular risk factor
Persistent insomnia: Difficulty sleeping lasting more than a few weeks despite lifestyle changes warrants a GP assessment to rule out underlying causes
Underlying conditions: Sleep problems can signal thyroid disorders, depression, anxiety or other medical issues requiring diagnosis and treatment
Frequently Asked Questions
How many hours of sleep do adults need?
Most adults need between seven and nine hours per night. However, sleep quality matters as much as duration. Consistently waking during the night or spending insufficient time in deep sleep can leave you feeling unrefreshed even after eight hours in bed.
Why do I wake up tired even after sleeping eight hours?
Waking up tired despite adequate hours in bed often points to poor sleep quality rather than insufficient duration. Common causes include sleep apnoea, an inconsistent sleep schedule, screen use before bed, alcohol consumption in the evening, or a bedroom that is too warm. If the problem persists, consider speaking to your GP.
Does poor sleep weaken your immune system?
Yes. During sleep your body produces cytokines and regenerates T cells, both of which are essential for fighting infection. A 2015 study found that adults sleeping fewer than six hours per night were over four times more likely to develop a cold after viral exposure compared to those sleeping seven hours or more.
Can lack of sleep cause weight gain?
Sleep deprivation disrupts the hormones that regulate appetite, increasing ghrelin (hunger) and reducing leptin (fullness). It also lowers motivation to exercise and impairs blood sugar regulation. Over time, chronic poor sleep is associated with weight gain and an increased risk of type 2 diabetes.
What is the best natural supplement for sleep?
Magnesium glycinate (bisglycinate) and ashwagandha KSM-66 are two of the most evidence-backed natural options. A 2024 randomised trial showed magnesium bisglycinate significantly improved deep sleep and sleep efficiency over 8 weeks. Ashwagandha helps reduce cortisol levels and supports sleep onset, particularly when stress is a contributing factor. Melatonin is also effective for resetting your sleep cycle after travel or shift work.
Is poor sleep linked to Alzheimer's disease?
Research published in Science (Xie et al., 2013) showed that the brain's glymphatic system clears beta-amyloid protein 60% more efficiently during sleep than during waking hours. Beta-amyloid is the waste product that forms the plaques associated with Alzheimer's disease. Chronic poor sleep may reduce this clearance over time, though more research is needed to confirm a direct causal link.
Does magnesium help you sleep?
Clinical evidence supports magnesium for sleep, particularly in the bisglycinate (glycinate) form. A 2024 randomised, placebo-controlled trial found that 250mg of magnesium bisglycinate taken before bed significantly improved sleep quality, deep sleep duration and sleep efficiency over 8 weeks. Magnesium activates the parasympathetic nervous system and the glycine component has independent calming properties.
Summary
Sleep affects virtually every aspect of your health. The research is clear: adults who consistently sleep fewer than seven hours face significantly higher risks of infection, cognitive impairment, cardiovascular disease and metabolic disruption.
The practical steps that make the biggest difference are consistent sleep and wake times, limiting caffeine and screens in the hours before bed, regular exercise, and a cool dark bedroom. If lifestyle changes are not enough, magnesium glycinate and ashwagandha KSM-66 both have clinical evidence supporting their use for sleep.
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