What Is a Sleep Log
A sleep log is a daily written record of your sleep and wake times, including time spent in bed, estimated time to fall asleep, number of nighttime awakenings, and total sleep duration. You record these entries each morning, typically for 1-2 weeks, to create a baseline picture of your sleep patterns.
Sleep logs differ slightly from sleep diaries in scope. A sleep log focuses on the quantitative data: when you slept, how long, and basic disruptions. A sleep diary captures those metrics plus subjective factors like mood, caffeine intake, and stress levels. Many people use these terms interchangeably, but clinicians often distinguish between them based on what information they need to diagnose your condition.
Why Clinicians Request Sleep Logs
Sleep logs are a first-line diagnostic tool for insomnia, sleep apnea screening, and circadian rhythm disorders. Before ordering polysomnography (an overnight lab test costing $1,500-$3,000), most sleep specialists ask patients to keep a 2-week sleep log. This data helps them determine whether testing is necessary and what specific protocols to use.
For CBT-I (cognitive behavioral therapy for insomnia), sleep logs are essential. You track sleep data weekly throughout treatment, typically over 6-8 weeks. Your therapist uses these entries to identify patterns, adjust sleep window recommendations, and measure whether interventions like stimulus control or sleep restriction are working. Studies show patients who maintain consistent sleep logs during CBT-I achieve 30-40% better outcomes than those who skip tracking.
Sleep logs also reveal your sleep efficiency, which is the percentage of time in bed that you actually sleep. If you spend 8 hours in bed but sleep only 5 hours, your efficiency is 63%. Sleep specialists typically target 85% or higher efficiency.
How to Keep an Accurate Sleep Log
- Record timing immediately upon waking: Write down your bedtime, estimated time to fall asleep (sleep onset latency), number of awakenings and their duration, final wake time, and total sleep duration. Don't guess these numbers hours later.
- Note your wake window: Record what time you got out of bed and stayed out. This matters because lying awake in bed reinforces the association between bed and wakefulness, which worsens insomnia.
- Track at least 14 consecutive nights: Two weeks is the minimum for identifying reliable patterns. Weekend sleep often differs significantly from weekday sleep, so you need both.
- Use a simple format: A notebook or basic spreadsheet works better than complex apps. Keep it by your bed so you complete entries before starting your day.
- Include relevant variables: If your clinician is evaluating sleep apnea risk, note snoring or witnessed apneas. For circadian rhythm disorders, record light exposure. For insomnia assessment, note caffeine timing and afternoon naps.
Common Questions
- How precise do my time estimates need to be? Within 15 minutes is sufficient. You're not expected to know exact seconds. Most people can estimate sleep onset and wake time fairly accurately after a few nights of practice.
- Should I use a sleep tracker device instead? Wearables and phone apps estimate sleep using motion detection, which often misses when you're lying still but awake. A manual sleep log captures your actual perception of sleep, which matters diagnostically. Your clinician may ask you to compare what you perceived with what your device shows, but don't rely on the device alone.
- What if my sleep schedule is irregular? Keep the log anyway. Extreme variation (sleeping 4 hours some nights and 9 hours others) itself is clinically important information that helps diagnose circadian rhythm disorders or behavioral insomnia.