Getting enough sleep is vital for our health and wellbeing. But in our busy modern lives, many of us struggle to get the recommended 7-9 hours per night. Some people even try to survive on just 4-5 hours sleep a night. But is this really enough?
How much sleep do we need?
The National Sleep Foundation recommends that adults aged 18-64 get 7-9 hours of sleep per night. Their guidelines state:
- 7-9 hours per night is recommended for optimal health and wellbeing
- Adults should avoid getting less than 6 hours or more than 10 hours per night on a regular basis
- Older adults aged 65+ may need 7-8 hours per night
These recommendations are based on extensive research into the health impacts of different sleep durations. Studies show that getting less than 7 hours sleep is associated with impaired cognitive function, increased risk of accidents, obesity, high blood pressure, heart disease, diabetes and premature mortality.
What happens when you don’t get enough sleep?
Not getting the recommended 7-9 hours can negatively impact nearly every system in your body:
Brain
- Impaired cognition, concentration, productivity and memory
- Increased risk of Alzheimer’s disease
Immune System
- Increased inflammation and reduced immune response
- Higher susceptibility to infections
Metabolism
- Imbalanced appetite hormones leading to weight gain
- Higher risk of obesity and diabetes
- Increased insulin resistance
Heart
- Increased blood pressure
- Increased risk of heart attack and stroke
Mood
- Increased anxiety, stress, irritability and depression
- Mood swings and emotional reactivity
Lack of sleep also makes you more prone to injuries and accidents. Studies show that being awake for 18 hours impairs your driving ability as much as having a blood alcohol level of 0.05% (legally drunk in many countries).
What are the effects of very little sleep (4-5 hours)?
Getting only 4-5 hours of sleep per night regularly is considered “very short sleep duration”. Research shows this can have the following effects on health and performance:
| Effect | Evidence |
|---|---|
| Impaired alertness and performance | Many studies show that with less than 5 hours sleep, cognitive performance declines rapidly each day without adequate recovery sleep. |
| Increased daytime sleepiness | Studies found that people who sleep 4-5 hours a night experience extreme sleepiness and have more lapses of attention during the day. |
| Weakened immune function | Lack of sleep appears to reduce natural killer cell activity and antibody responses, increasing susceptibility to the common cold and other infections. |
| Increased inflammation | Reduced sleep is linked to higher inflammatory markers like C-reactive protein, which may increase risk of cancer, diabetes, cardiovascular disease. |
| Weight gain and obesity | Getting less than 5 hours of sleep alters appetite-regulating hormones like leptin and ghrelin, promoting obesity over time. |
| Increased mortality risk | Several studies link very short sleep duration (less than 5 hours) to a significantly increased risk of death from all causes. |
The evidence clearly shows that restricted sleep of just 4-5 hours per night is not sustainable in the long-term without serious health and safety consequences.
Tips for surviving short-term sleep restriction
Occasionally we all have a night or two of very short sleep due to work, family or other demands. Here are some tips to get through:
- Nap opportunistically – take 15-20 minute naps when you have the chance to relieve fatigue.
- Prioritize high value tasks – focus on your most important work and leave menos tasks for later.
- Avoid driving – get transport to minimize accident risk from drowsiness.
- Get sunlight – exposure to bright light during the day can improve alertness and performance.
- Avoid alcohol – drinking alcohol when sleep deprived worsens cognitive and motor impairment.
- Consume caffeine carefully – 1-2 cups of coffee can help counteract sleepiness for short periods.
- Take a power nap – naps as short as 10 minutes can improve alertness and performance for 2-3 hours.
However, these tips only help manage the effects of short-term sleep loss. The only long-term solution is to ensure you get adequate sleep of 7-9 hours as often as possible.
The risks of relying on 4.5 hours sleep
Trying to routinely survive on just 4.5 hours sleep carries some significant risks and pitfalls:
- You will accumulate a chronic sleep debt that can’t be easily recovered from with a single long sleep.
- Cognitive deficits accumulate and mental performance continues declining without sufficient sleep.
- Short sleep durations become your “new normal” as the brain adjusts to expect less sleep.
- You may underestimate the impairments caused by sleep deprivation and take dangerous risks like driving while extremely fatigued.
- Rates of anxiety, depression, irritability and stress increase over time without adequate sleep.
- Immune function weakens and your body becomes more susceptible to sickness and disease.
Research confirms that routinely getting less than 6 hours sleep leads down a vicious cycle. You feel compelled to sleep less to pack more into your days, which only amplifies the hunger for sleep. This leads to even more sleep deprivation over time.
Healthy sleep habits for sufficient sleep
If you struggle to get enough sleep at night, try adopting these healthy sleep habits:
- Go to bed and wake up at a consistent time, even on weekends.
- Make sure your bedroom is cool, quiet and dark for better sleep.
- Avoid exposure to blue light from electronics before bedtime.
- Cut back on stimulating foods, drinks and activities in the evenings.
- Exercise regularly, but not too close to bedtime.
- Relax your mind with meditation, music or reading before bed.
- Keep naps short if you need one and before 3pm.
- See your doctor if you suspect you have a sleep disorder.
Focus on winding down, limiting distractions and creating an environment conducive for sleep. This will make it easier to get the 7-9 hours of sleep you need.
Conclusion
Research clearly shows that regularly getting just 4.5 hours sleep is not enough for most adults to sustain cognitive performance, health and wellbeing. While an occasional short night of sleep won’t do much harm, relying on very restricted sleep of under 5 hours risks significant impairments to brain function, weakened immunity, metabolic disorders and safety issues. It’s best to prioritize getting at least 6, and ideally 7-9, hours of sleep per night through healthy sleep habits for optimal health and daily performance.