Sleep is a biological necessity, not a luxury. During sleep, the body repairs tissue, consolidates memories, regulates hormones, and clears metabolic waste products from the brain through the glymphatic system. Chronic sleep deprivation is associated with increased risk of cardiovascular disease, type 2 diabetes, obesity, impaired immunity, and mental health disorders.

Despite this, sleep is one of the most commonly sacrificed health behaviours in modern life. Many people focus on duration — hours of sleep — while overlooking quality. Poor-quality sleep, even at adequate duration, fails to deliver the restorative benefits of healthy sleep architecture.

A sleep quality tracker goes beyond simply recording bedtime and wake time. It captures sleep efficiency, onset latency, wake-after-sleep-onset (WASO), disturbances, and subjective quality to produce a composite picture of how restorative each night's sleep actually was.

The tracker calculates a composite sleep quality score from three weighted components: sleep efficiency (50%), subjective quality rating (30%), and a disturbance penalty (20%). Each component is normalised to a 0–100 scale before weighting.

Sleep efficiency = Total sleep time ÷ Time in bed × 100. High-quality sleepers typically achieve 85% or above. Consistently below 80% efficiency suggests difficulty falling or staying asleep and may indicate a clinical sleep disorder worth investigating.

Subjective quality is your own rating on a 1–5 scale — a deliberately simple capture of how rested you felt on waking. This subjective dimension matters because two people with identical polysomnography data can report very different sleep experiences.

The disturbance penalty deducts up to 40 points based on the number of awakenings or disturbances logged. Each disturbance contributes approximately 8 points of penalty, reflecting that fragmented sleep — even of adequate total duration — significantly reduces restorative value.

A score of 85 or above is classified as Excellent — reflecting high sleep efficiency, minimal disturbances, and a strong subjective sense of restoration. This is the target for consistently restorative sleep.

70–84 is classified as Good — most nights in this range indicate generally healthy sleep with room for minor improvement. Common contributors to scores in this range include occasional awakenings or a slightly longer-than-ideal sleep onset.

50–69 is Fair — suggesting meaningful room for improvement. Consistently fair sleep often points to identifiable lifestyle factors such as late caffeine intake, screen use before bed, irregular sleep schedules, or underlying stress.

Below 50 is Poor — indicating significant sleep disruption. Persistent poor scores over multiple weeks warrant consideration of sleep hygiene review and, if no clear lifestyle cause is identified, clinical sleep assessment.

Keep a consistent schedule. Going to bed and waking at the same time every day — including weekends — is among the most effective single interventions for improving sleep quality. It strengthens the circadian rhythm and makes falling asleep easier.

Optimise the sleep environment. A dark, cool (16–19°C / 61–66°F), and quiet room supports sleep onset and maintenance. Blackout curtains, earplugs, or a white noise machine can meaningfully improve sleep quality in challenging environments.

Limit screens before bed. Blue light emitted by screens suppresses melatonin production and delays circadian phase. Avoiding screens for at least 60 minutes before bed is widely recommended; enabling night mode or using blue-light-blocking glasses provides partial mitigation if screen avoidance is impractical.

Avoid caffeine after early afternoon. With a half-life of 5–7 hours, a coffee consumed at 3 pm still contributes 50% of its caffeine at 8–10 pm. Cutting off caffeine by early afternoon significantly reduces sleep-onset difficulty for sensitive individuals.

Reserve the bed for sleep. Working, watching television, or using a phone in bed trains the brain to associate the bed with alertness rather than sleep — a pattern that drives conditioned insomnia. Keeping the bed exclusively for sleep (and intimacy) strengthens this association over time.