Poor sleep can mean two things. First, it can mean getting too little sleep. Most people need approximately 8 hours per night. Older people can do with a bit less. Second, it can mean low-quality sleep. Often this means that you wake up during the night and that the normal built up of your sleep is disrupted. Normal sleep happens in 5 stages which are gone through multiple times during the night. People with depressive symptoms often have briefer deep sleep and intensified REM sleep.
A range of problems can happen in your functioning when you don't get enough quality sleep. It can result in mood problems (depressive symptoms) and a lowering of your pain threshold (due to which you may be more at risk for chronic pain). In addition to that, your concentration and your memory function deteriorate due to which learning becomes harder. Also, your capacity to make decisions and to control your impulses suffer and you become more likely to display addictive behaviors. Finally, poor sleep can lead to higher blood pressure, a reduced immune system function, and an increased risk for heart disease and overweight.
It is visible in the brain that the work of specific neural circuits is altered with poor sleep; in particular the communication between two areas in the prefrontal cortex (PFC; the dorsomedial and ventrolateral PFC) and the hippocampus, a structure in the limbic system). Because of the reduced activity in the PFC, activity in the hippocampus is less regulated due to which continuous sleep becomes harder. Furthermore, is visible in the brain that the levels of several neurotransmitters is altered by poor sleep, in particular serotonine (plays a role in willpower, motivation, and mood), dopamine (plays a role in enjoyment and habit formation), norepinephrine (important for thinking, focus, and coping with stress), and endorfines (reduces pain).
In order to improve their sleep people often use certain substances like alcohol and medication to affect the above-mentioned processes and neurotransmitter levels. Such substances can seem to work in the short term but often have side effects and their efficacy may lessen over time. Fortunately there are many things you can do without such substances to improve your sleep. Below, I paraphrase Korb's tips and categorize them in my own way.
- Utilize light: Make sure to get much light during the day (preferably sunlight). This stimulates the production of melatonine (a substance which is released at night to prepare you for sleep). When your bedtime approaches, turn your lights a bit down. This helps to start releasing the melatonine.
- Exercise: make sure you get much physical activity during the day and start becoming less active in the evening.
- Eating and drinking: eat and drink only moderately and avoid alcohol and caffeine before going to bed.
- Bedtime routine: by developing a bedtime routine you condition your brain to sleep better. Decide what your normal bedtime is and stick to that. Make sure your bedroom is comfortable, clean, dark and silent. Go through a number of steps before going to bed. Use your bed for sleeping, not for watching TV or surfing the internet.
- Step by step: if you don't succeed right away in sleeping 8 hours straight on, start with fewer hours and gradually lengthen you sleep. Try to relax while falling asleep. If that does not work because you are worrying about something, get up, go to another room, do something relaxing for half an hour and try again.