Explain which additional factors should be explored in order to explain the variation in sleep.

To explain sleep variation, we need to consider lifestyle choices and environmental factors. For example, diet and physical activity can significantly impact one’s ability to fall asleep at night; a pattern of unhealthy eating habits or inadequate exercise can lead to poor quality sleep. Additionally, exposure to light and sound at bedtime or during the day can affect an individual’s circadian rhythm which will have an effect on their amount of restful sleep. Stressors such as financial stress or interpersonal problems can also cause difficulty sleeping or difficulties staying asleep through the night. For possible causes of sleeping problems, it is important to check for underlying medical conditions like depression, anxiety, asthma/allergy symptoms and heart disease.