Sleep is a biological necessity and good sleep is essential for good physical, mental and emotional health. Women's sleep is affected in different ways compared with men's because of biological and psychosocial influences, and women's sleep changes at different stages of their lives. Sleep disorders in women are often overlooked by doctors: for example, sleepdisordered breathing is commonly associated with middle-aged men, but around 10% of women also suffer from it.

Insomnia and mental health problems often go together. Poor sleep has been linked with an increased risk of depression and anxiety and, in turn, insomnia is common in both anxiety and depression (Neckelmann et al, 2007).

Stages of sleep

Sleep is divided into two distinct states: rapid eye movement (REM) sleep and non-REM sleep. Non-REM sleep is further divided into three stages. During the night you pass through the four sleep stages (1, 2, 3 and REM sleep) in what are known as sleep cycles. Each cycle lasts an average of 90–110 min. The first sleep cycles of the night have long periods of deep sleep and relatively short periods of REM sleep. Later in the night, however, the periods of REM sleep lengthen and deep sleep is mostly absent.

Stage 1 sleep

Stage 1 sleep (3–7% of sleep) is the lightest stage of sleep and is the transition between wake and sleep. The eyes move slowly back and forth and muscle activity reduces.

Stage 2 sleep

In Stage 2 sleep (45–50% of sleep), the slow, rolling eye movements seen in Stage 1 sleep stop. Brain waves become slower, with only occasional bursts of rapid brain waves.

Stage 3 sleep

In Stage 3 sleep (25% of sleep), sleep becomes deeper and extremely slow brain waves (called delta waves) appear. This is the deepest, most restorative stage of sleep and is most closely linked with the part sleep plays in making us feel well-rested and energetic during the day. Deep sleep is also important for memory and learning.

REM sleep

In REM sleep (20–25% of sleep), the eyes jerk rapidly back and forth under closed eyelids (hence its name). It is during REM sleep that most story-like dreams occur. Everyone dreams every night, and we have three to five periods of REM sleep each night.