You spend more time in stages 1 and 2 of NREM sleep and less time in stages 3 and 4. Because you're sleeping lighter, you're also more easily awakened. You get tired earlier in the evening and consequently wake up earlier in the morning. A change in activity. You may be less physically or socially active.
Activity helps promote a good night's sleep.
You may also have more free time and, because of that, drink more caffeine or alcohol or take a daily nap. These factors can also interfere with sleep at night. A change in health. Chronic pain associated with conditions such as arthritis or back problems can interfere with sleep. Depression, anxiety and ongoing stress also can contribute to insomnia.