Does the Sleep Regularity Questionnaire capture objective sleep-wake regularity? Evidence from wearable and sleep diary data.

This study finds that while the Sleep Regularity Questionnaire shows modest agreement with subjective sleep diary measures, it demonstrates only weak correspondence with objective smart ring data, suggesting it is best used as a complementary tool rather than a replacement for objective monitoring in healthy adults.

The Gist

The Big Question: Can a Questionnaire Measure Your Sleep "Rhythm"?

Imagine your sleep schedule is like a metronome (the little device musicians use to keep a steady beat). A "regular" sleeper has a metronome that ticks perfectly at the same time every night. An "irregular" sleeper has a metronome that speeds up, slows down, or skips beats randomly.

Scientists know that having a steady sleep rhythm is crucial for your health, just like a steady beat is crucial for a song. Usually, to measure this rhythm, you have to wear a high-tech gadget (like a smart ring) that watches you sleep for weeks. This is accurate, but it's expensive and annoying.

So, researchers asked: Can we just ask people, "Do you feel like you have a steady sleep rhythm?"

They tested a short questionnaire called the Sleep Regularity Questionnaire (SRQ) to see if people's feelings about their sleep schedule matched the actual data from the smart rings.

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The Experiment: Two Different Ways to Look at the Same Thing

The researchers split the study into two parts, like testing a new recipe with two different groups of tasters.

Part 1: The "Smart Ring" Group (The Objective Truth)

• Who: 31 healthy adults.
• What they did: They wore a smart ring (like a high-tech wedding band) on their finger for 21 nights straight.
• The Tech: The ring didn't just guess; it measured movement and heart rate to know exactly when they fell asleep and woke up. It calculated a "Sleep Regularity Index" (SRI)—a math score of how consistent their sleep was.
• The Test: After the 21 nights, the participants filled out the SRQ questionnaire, rating how regular they thought their sleep was.

The Result:
The correlation was weak.

• The Analogy: Imagine you ask a runner, "Do you feel like you ran a steady pace today?" The runner says, "Yes, I felt very steady!" But when you check the GPS watch, the runner actually sprinted, jogged, and stopped for water randomly.
• What happened: People who felt very regular on the questionnaire often had messy, irregular data on their smart rings. The questionnaire didn't capture the "math" of the sleep rhythm very well.

Part 2: The "Sleep Diary" Group (The Subjective Truth)

• Who: 52 healthy adults.
• What they did: They didn't wear a ring. Instead, they kept a sleep diary for one week, writing down what time they went to bed, woke up, and how they felt.
• The Test: They also filled out the SRQ questionnaire.

The Result:
The correlation was better, but still modest.

• The Analogy: This time, the runner is asked, "Did you feel steady?" and they also write down their times in a notebook. The runner's feeling of steadiness matched their written notes better than the GPS watch did.
• What happened: People who felt their sleep was regular also reported better sleep quality in their diaries. However, the questionnaire still didn't perfectly predict the exact minute-to-minute variability in their sleep times.

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The Key Takeaways (The "So What?")

1. Feelings vs. Facts
The study found that how you feel about your sleep schedule is different from what your body is actually doing.

• Metaphor: Think of the SRQ as a weather forecast based on how the air feels on your skin. It's good for a general idea ("It feels like a rainy day"), but it's not as accurate as a satellite (the smart ring) that sees the actual clouds and rain.

2. The Questionnaire is Good for "Vibes," Not "Data"
The SRQ is great at predicting how tired or refreshed you feel (your sleep quality). If you say, "I have a very regular schedule," you probably do feel like you sleep well.

• However, if you need to know the exact scientific data of your sleep rhythm (for medical diagnosis or elite sports training), the questionnaire isn't precise enough.

3. Why the Mismatch?
Why didn't the questionnaire match the ring?

• Memory is fuzzy: Humans are bad at remembering small details. You might think, "I wake up at 7:00 AM every day," but the ring sees you waking up at 6:45, 7:15, and 7:05. To you, that's "regular." To the ring, that's "variable."
• Different definitions: The questionnaire asks about your general routine over weeks. The ring measures exact seconds over days. They are measuring slightly different things.

The Bottom Line

The Sleep Regularity Questionnaire is a useful, quick tool for doctors or coaches to get a "gut check" on a person's sleep habits. It tells you if someone thinks they have a good routine and if they feel rested.

But, it cannot replace the smart ring.
If you need to know the true, objective regularity of your sleep (like a pilot checking the instruments before a flight), you still need the technology. The questionnaire is the passenger's opinion; the smart ring is the flight data recorder.

In short: The questionnaire is a good companion to the technology, but it's not a substitute. Use the questionnaire to start a conversation, but use the data to make the final decision.

Technical Summary

1. Problem Statement

Sleep regularity (the consistency of sleep–wake timing) is a critical, yet under-measured, dimension of sleep health linked to cardiometabolic risk, cognitive function, and mental health. While objective metrics derived from actigraphy and wearables (e.g., Sleep Regularity Index [SRI], Interdaily Stability [IS]) are robust, they are resource-intensive, require specialized data processing, and are often inaccessible in large-scale or clinical settings.

The Sleep Regularity Questionnaire (SRQ) was developed as a brief, subjective tool to assess perceived sleep consistency. However, its convergent validity against high-resolution objective indices and its ability to capture the same underlying construct as device-derived metrics in healthy adults remain unclear. This study aims to validate the SRQ against both objective wearable data and subjective sleep diary data.

2. Methodology

The study employed a two-part observational validation design involving 83 unique healthy adults (aged 20–65) who were not shift workers.

Part 1: Objective Validation (Wearable Data)

• Sample: 31 adults.
• Protocol: Continuous monitoring for 21 nights using the Ultrahuman Ring AIR (smart ring).
• Objective Metrics:
  • Sleep Regularity Index (SRI): Calculated using a custom Python implementation adhering to the RIRI (Reporting Items for Regularity Indices) checklist (noon-to-noon, 5-minute epochs, binary sleep/wake states).
  • Interdaily Stability (IS): Non-parametric metric for circadian rhythm strength.
  • Social Jetlag (SJL): Difference in mid-sleep between workdays and free days.
  • Composite Phase Deviation (CPD): Night-to-night irregularity in sleep timing.
  • Timing Variability: Standard deviation (SD) of bedtime and wake time.
• Subjective Measures: SRQ (6-item version: Circadian Regularity and Sleep Continuity subscales) and Brief Pittsburgh Sleep Quality Index (B-PSQI).

Part 2: Diary-Based Validation

• Sample: 52 adults.
• Protocol: 7-night sleep diary recording habitual bedtime, wake time, total sleep time (TST), and perceived sleep quality.
• Derived Metrics: Weekly SDs of bedtime, wake time, mid-sleep, and TST; mean perceived sleep quality; and SJL.
• Subjective Measures: SRQ and B-PSQI.

Statistical Analysis

• Part 1: Pearson correlations between SRQ scores and objective device metrics.
• Part 2: Spearman rank correlations between SRQ scores and diary metrics, with False Discovery Rate (FDR) correction (Benjamini–Hochberg).
• Secondary Analysis: Receiver Operating Characteristic (ROC-AUC) analysis to test if SRQ could discriminate individuals with high sleep-timing variability (top tertile).

3. Key Contributions

• RIRI-Compliant Analysis: The study explicitly applied the RIRI checklist to the calculation of the SRI from wearable data, addressing recent concerns about the lack of standardization in regularity indices (e.g., epoch length, day definition, nap handling).
• Dual-Mode Validation: It is the first study to directly compare the SRQ against both high-resolution wearable-derived regularity indices and diary-derived variability metrics in healthy adults.
• Construct Differentiation: The study provides evidence that the SRQ measures a construct related to, but distinct from, objective 24-hour state regularity.

4. Key Results

Part 1: Wearable vs. SRQ

• Weak Objective Correlation: Associations between SRQ scores (Global, Circadian, and Continuity) and device-derived metrics (SRI, IS, SJL, CPD, timing variability) were small to negligible ($|r| \le 0.36$).
  • Correlations with SRI and IS were particularly weak ($r \approx 0.01 - 0.17$, $p > 0.35$).
  • The strongest correlation was between SRQ Circadian Regularity and Social Jetlag ($r = 0.36, p = 0.049$), though this is likely due to the SRQ capturing consistency within days rather than the shift between work/free days.
• Stronger Subjective Correlation: SRQ scores showed moderate inverse associations with the B-PSQI (Global sleep quality), particularly the Sleep Continuity subscale ($r = -0.44$). This indicates that while the SRQ does not predict objective regularity well, it aligns with how individuals perceive their overall sleep quality.

Part 2: Diary vs. SRQ

• Moderate Diary Correlations: SRQ Global and Circadian Regularity showed small-to-moderate associations with higher diary-rated perceived sleep quality ($r \approx 0.41$).
• Timing Variability: There were small negative correlations between SRQ scores and bedtime variability ($r \approx -0.32$ to $-0.34$), but these did not survive FDR correction.
• Discrimination Utility: The SRQ performed poorly at identifying individuals with high sleep-timing variability (ROC-AUC $\approx 0.52$, essentially chance).

5. Significance and Conclusion

Main Conclusion:
The Sleep Regularity Questionnaire (SRQ) does not capture objective sleep–wake regularity as measured by wearables in healthy adults with relatively regular schedules. Instead, the SRQ appears to measure a subjective sense of sleep stability that correlates more strongly with perceived sleep quality (B-PSQI) and diary-rated consistency than with high-resolution physiological regularity indices (SRI, IS).

Implications:

1. Complementary, Not Substitutive: The SRQ should be viewed as a tool to complement, rather than replace, objective monitoring (actigraphy/wearables) when precise quantification of 24-hour state regularity is required.
2. Construct Validity: The SRQ captures a "perceived regularity" construct that is distinct from the "state probability" construct of the SRI. Individuals may perceive their sleep as regular even if their device data shows irregularity at the margins of the sleep window.
3. Future Directions: The SRQ may be more valid in populations with greater irregularity (e.g., shift workers, clinical populations with circadian disorders) where the range of variability is wider. Future research should test the SRQ's responsiveness to interventions targeting sleep regularity.

Limitations:

• Restricted Range: The sample consisted of healthy adults with relatively regular sleep patterns (high SRI, low SJL), which may have attenuated correlations.
• Sample Size: The wearable subsample ($n=31$) was modest, limiting statistical power for detecting small effect sizes.
• Cross-Sectional: The study cannot determine the SRQ's sensitivity to change over time.