Sleep quality refers to how well a person sleeps, encompassing not just the duration of sleep but also how restorative, efficient, and undisturbed that sleep is. It is a multidimensional concept that is distinct from sleep quantity — a person can sleep for many hours and still experience poor sleep quality, or sleep for fewer hours and wake feeling genuinely refreshed. Key dimensions of sleep quality include sleep onset latency (how quickly a person falls asleep), sleep continuity (how few awakenings occur during the night), sleep efficiency (the proportion of time in bed actually spent asleep), the distribution of sleep stages (including adequate amounts of deep sleep and REM sleep), and how the person feels upon waking and throughout the following day. Poor sleep quality can result from a wide range of causes, including stress and anxiety, sleep disorders such as insomnia or sleep apnea, environmental disturbances such as noise and light, uncomfortable bedding, excessive alcohol or caffeine consumption, irregular sleep schedules, and underlying health conditions. The consequences of consistently poor sleep quality can be significant, including daytime fatigue, difficulty concentrating, mood disturbances, impaired immune function, and increased long-term risk of cardiovascular disease, metabolic disorders, and mental health conditions. Improving sleep quality involves addressing its underlying causes and adopting good sleep hygiene practices — maintaining a consistent sleep schedule, creating an optimal sleep environment, establishing a calming bedtime routine, and limiting factors that disrupt sleep. If poor sleep quality persists despite these measures, consulting a doctor or sleep specialist is advisable.