Higher Body Weight Predicts Very Slightly Higher Sleep Efficiency for Population

Higher Body Weight Predicts Very Slightly Higher Sleep Efficiency for Population

Contents

Variables

A
Body Weight 1140
A
Sleep Efficiency 1854

Categories

A
Physique 41
A
Sleep 111

Tags

High Confidence
Very Weak Effect Size
Positive Relationship
Population Study
cause image gauge image effect image
Participants reported a 0.9% average increase in Sleep Efficiency following above average Body Weight.

Abstract

Sleep Efficiency was generally 2% higher than average after an average of 174 pounds of Body Weight over the previous 7 days.

Aggregated data from 103 study participants suggests with a HIGH degree of confidence (p=0.084, 95% CI -1.255 to 1.365) that Body Weight has a very weakly positive predictive relationship (R=0.0548) with Sleep Efficiency.

The highest quartile of Sleep Efficiency measurements were observed following an average 180 pounds Body Weight.

The lowest quartile of Sleep Efficiency measurements were observed following an average 180 pounds of Body Weight.

After an onset delay of 0 seconds, Sleep Efficiency is typically 2% lower than average over the 7 days following around 180 pounds of Body Weight Body Weight.

Keywords: Body Weight, Sleep Efficiency, N-of-1 trials, real-world evidence, causal inference, observational study

High Confidence: With 103 participants, these findings have strong statistical power.

Results

Primary Findings

Analysis of 21,845 paired observations from 103 participants revealed a minimal reduction in Sleep Efficiency following above-average Body Weight exposure.

-0.1%
Change from Baseline
Minimal effect on Sleep Efficiency
0.53
Predictor Impact Score
Strong evidence for causal relationship

Supporting Statistics

High
Confidence
0.055
Correlation (r)
p = 0.641
Significance
z = 0.89
Effect Magnitude
φ = 0.84
Temporality

What This Means

When participants had above-average Body Weight:

  • Sleep Efficiency decreased by 0.1% on average
  • The Predictor Impact Score of 0.53 suggests this relationship warrants high priority for experimental validation
  • Temporal analysis supports Body Weight as the predictor (not the outcome)

Interpreting the Predictor Impact Score

The Predictor Impact Score (PIS) integrates multiple Bradford Hill causal criteria into a single metric. Use this guide to interpret the score:

PIS Range Interpretation Recommended Action
≥ 0.5 Strong evidence High priority for RCT validation
0.3 - 0.5 Moderate evidence Consider for experimental investigation
0.1 - 0.3 Weak evidence Monitor for additional data
< 0.1 Insufficient evidence Low priority; may be noise

Note: PIS is a prioritization heuristic, not proof of causation. High scores indicate relationships worth investigating, not confirmed causal effects.

Optimal Daily Values

No clear dose-response relationship detected. The Body Weight values associated with high and low Sleep Efficiency are too similar to provide meaningful dosing guidance. This may indicate a threshold effect (any amount works equally well), no effect, or insufficient data variance.

Population Correlation

Body Weight Distribution

Sleep Efficiency Distribution

Relationship Analysis

Statistical Summary

Relationship Statistics

Property Value
Cause Variable Name Body Weight
Effect Variable Name Sleep Efficiency
Sinn Predictive Coefficient 0.52738226192646
Confidence Level HIGH
Confidence Interval 1.3097549915398
Forward Pearson Predictive Coefficient 0.0548
Critical T Value 1.6650776699029
Average Body Weight Over Previous 7 days Before ABOVE Average Sleep Efficiency 180 pounds
Average Body Weight Over Previous 7 days Before BELOW Average Sleep Efficiency 180 pounds
Duration of Action 7 days
Effect Size very weakly positive
Number of Paired Measurements 21845
Optimal Pearson Product 0.18659722881162
P Value 0.084007665485398
Statistical Significance 0.6406
Strength of Relationship 1.3097549915398
Study Type population
Analysis Performed At 2026-01-04
Number of Participants 103

Body Weight Info

Property Value
Variable Name Body Weight
Aggregation Method MEAN
Analysis Performed At 2020-09-23
Duration of Action 7 days
Kurtosis 29.271534088526
Maximum Allowed Value 1000 pounds
Mean 168.9619340574 pounds
Median 168.27481272906 pounds
Minimum Allowed Value 0 pounds
Number of Aggregate Predictors 883
Number of Aggregate Outcomes 257
Number of Measurements 108822
Number of Measurements (including those generated by tagged, joined, or child variables) 21092
Public true
Onset Delay 0 seconds
Standard Deviation 8.7190661755282
Unit Pounds
User Variables 417
UPC 875011003902
Variable Category Physique
Variable ID 1486
Variance 594.35417755402

Sleep Efficiency Info

Property Value
Variable Name Sleep Efficiency
Aggregation Method MEAN
Analysis Performed At 2020-10-11
Duration of Action 24 hours
Kurtosis 7.3216313398995
Mean 86.964972477359 percent
Median 87.801418439716 percent
Minimum Allowed Value 1 percent
Number of Aggregate Predictors 1698
Number of Aggregate Outcomes 156
Number of Measurements 22620
Number of Measurements (including those generated by tagged, joined, or child variables) 1914
Public true
Onset Delay 0 seconds
Standard Deviation 5.9209578901457
Unit Percent
User Variables 147
UPC 878881000699
Variable Category Sleep
Variable ID 5211811
Variance 75.785458915098

Introduction

Background

Body Weight (Physique) and Sleep Efficiency (Sleep) are both important factors in understanding human health and well-being. This study investigates the relationship between these two variables using real-world observational data.

Traditional randomized controlled trials (RCTs), while the gold standard for causal inference, are often impractical, expensive, or unethical for studying many health relationships. Aggregated N-of-1 observational studies offer a complementary approach that leverages within-subject comparisons across large populations to identify meaningful patterns.

Research Question

Does Body Weight affect Sleep Efficiency?

Additionally, we seek to determine:

  1. What is the direction and magnitude of any effect?
  2. How confident can we be in this relationship based on the available data?
  3. What are the optimal levels of Body Weight for maximizing Sleep Efficiency?

Study Objective

The objective of this study is to determine the nature of the relationship (if any) between Body Weight and Sleep Efficiency. Additionally, we attempt to determine the Body Weight values most likely to produce optimal Sleep Efficiency values.

Study Overview

This is a population-level observational study using aggregated N-of-1 methodology. By aggregating individual N-of-1 experiments, we can identify population-level patterns while accounting for the substantial individual variation that exists in most health relationships. Effect sizes are reported as percent change from baseline, enabling intuitive interpretation and comparison across different measures.

Full Methodology: Framework for Real-World Evidence-Based Pharmacovigilance: Aggregated N-of-1 Trials for Quantifying Treatment Effects

Discussion

Interpretation of Findings

Participants experienced a 0.1% reduction in Sleep Efficiency following above-average Body Weight exposure. The Predictor Impact Score (PIS) of 0.53 indicates strong evidence for a causal relationship.

Statistical Significance

Using a two-tailed t-test with alpha = 0.05, it was determined that the change in Sleep Efficiency is statistically significant at a 95% confidence interval. The p-value of 0.6406 indicates there is less than a 64.06% probability that this result occurred by chance.

After treatment, a 0.9% increase (-0.0623 percent) from the mean baseline 88.5 percent was observed. The relative standard deviation at baseline was 3.95534%. The observed change was 0.891913 times the standard deviation.

A common rule of thumb considers a change greater than twice the baseline standard deviation on two separate pre-post experiments may be considered significant. This occurrence would have only a 5% likelihood of resulting from random fluctuation (a p-value < 0.05).

T-Test Details
Observed t-value: 4.466
Critical t-value: 1.665

Since t = 4.47 > 1.67, we reject the null hypothesis.

Biological Plausibility

A plausible bio-chemical mechanism between predictor and outcome is critical for interpreting observational findings. This is where human judgment excels beyond statistical analysis.

Based on community responses so far, 1 person feels that there is a plausible mechanism of action and 0 feel that any relationship observed between Body Weight and Sleep Efficiency is coincidental.

Bradford Hill Criteria Assessment

The Bradford Hill criteria provide a framework for assessing causality in observational studies. Our methodology operationalizes six of the nine criteria through the Predictor Impact Score (PIS):

Criterion How Addressed Metric
Strength Effect size magnitude Percent change from baseline (Δ%), z-score
Consistency Cross-participant replication Number of users (N), number of pairs (n)
Temporality Predictor precedes outcome Temporality factor (φ), onset delay (δ > 0)
Biological Gradient Dose-response relationship Gradient coefficient (φgradient)
Plausibility Biological mechanism assessment Community votes on mechanism plausibility
Specificity Category appropriateness Interest factor (finterest)

Predictor Impact Score (PIS)

The PIS integrates multiple Bradford Hill criteria into a composite metric quantifying how reliably a predictor affects an outcome. Higher scores indicate stronger evidence:

Population-Level PIS:

$$\text{PIS}_{\text{agg}} = |r_{\text{forward}}| \cdot w \cdot \phi_{\text{users}} \cdot \phi_{\text{pairs}} \cdot \phi_{\text{change}} \cdot \phi_{\text{gradient}}$$

Where φ-factors are saturation functions approaching 1 as evidence accumulates:

  • φusers = 1 - e-N/10 (user saturation)
  • φpairs = 1 - e-n/nsig (pair saturation)
  • φchange = 1 - e-Δspread/Δsig (effect spread saturation)
  • w = weighted average of plausibility votes

Temporality Assessment

We assess evidence for correct causal direction using the temporality factor:

$$\phi_{\text{temporal}} = \frac{|r_{\text{forward}}|}{|r_{\text{forward}}| + |r_{\text{reverse}}|}$$

Values approaching 1 indicate the predictor precedes the outcome (supporting causation); values near 0.5 suggest ambiguous directionality; values near 0 suggest reverse causation or confounding by indication.

Limitations

As with any observational study, correlation does not prove causation. Key limitations include:

  • Unmeasured confounders: Variables not tracked may influence results
  • Self-selection bias: Health trackers may differ from the general population
  • Measurement error: Self-reported data may contain recall bias
  • Confounding by indication: Sicker individuals may use more treatments

However, within-subject comparison and temporal precedence analysis partially mitigate these limitations. If the relationship is merely coincidental, as participants independently modify their Body Weight values, the observed strength will decline over time. Spurious correlations naturally dissipate as more data is collected.

Future Directions

Future research should examine:

  • Subgroup analyses to identify individual differences in response
  • Potential confounders and mediators of the observed relationship
  • Optimal dosing and timing for Body Weight
  • Confirmation through prospective or randomized designs
  • Biological mechanisms underlying the observed effects

Conclusion

Above-average Body Weight was associated with a 0.1% reduction in Sleep Efficiency—a minimal effect. The Predictor Impact Score of 0.53 indicates this relationship is high priority for experimental validation.

Bottom Line: Based on a PIS of 0.53 and a 0.1% effect size, this relationship shows strong evidence and should be prioritized for experimental validation through randomized controlled trials.

These findings contribute to our understanding of how Body Weight may influence Sleep Efficiency in real-world conditions. The combination of effect size, sample size, and temporal evidence supports this as a meaningful relationship worth investigating further.

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Methods

Study Design

This study is based on data donated by 103 participants. Thus, the study design is equivalent to the aggregation of 103 separate n=1 observational natural experiments.

This within-subject design is powerful because it controls for all stable individual characteristics (genetics, baseline health status, socioeconomic factors) that might otherwise confound the relationship between variables.

Data Analysis

Temporal Assumptions

The analysis incorporates temporal assumptions about the relationship between variables:

  • Onset Delay: It was assumed that 0 seconds would pass before a change in Body Weight would produce an observable change in Sleep Efficiency.
  • Duration of Action: It was assumed that Body Weight could produce an observable change in Sleep Efficiency for as much as 7 days after the stimulus event.

Statistical Methods

For each participant, we calculated the Pearson correlation coefficient between Body Weight values and subsequent Sleep Efficiency values. Individual correlations were then aggregated using Fisher's z-transformation to produce a population-level estimate:

Individual Correlation:

$$r_i = \frac{\sum(x_{ij} - \bar{x}_i)(y_{ij} - \bar{y}_i)}{\sqrt{\sum(x_{ij} - \bar{x}_i)^2 \sum(y_{ij} - \bar{y}_i)^2}}$$

Fisher's Z-Transformation:

$$z_i = \frac{1}{2} \ln\left(\frac{1 + r_i}{1 - r_i}\right)$$

Aggregated Correlation:

$$\bar{r} = \tanh(\bar{z}) \quad \text{where} \quad \bar{z} = \frac{1}{N}\sum_{i=1}^{N} z_i$$

Effect Size Calculation

Effect sizes are reported as percent change from baseline. For each participant, we compare the outcome following above-average predictor values to the overall baseline outcome:

$$\Delta\%_{\text{baseline}} = \frac{\bar{O}_{\text{follow-up}} - \bar{O}_{\text{baseline}}}{\bar{O}_{\text{baseline}}} \times 100$$

Effect Magnitude (Z-Score)

To assess effect magnitude relative to natural variability, we calculate the z-score:

$$z = \frac{|\Delta\%_{\text{baseline}}|}{\text{RSD}_{\text{baseline}}}$$

where RSDbaseline is the relative standard deviation of outcome during baseline period

A z-score > 2 indicates statistical significance (p < 0.05), meaning the observed change exceeds typical baseline fluctuation and is unlikely due to random variation.

Statistical Significance

Correlation significance is assessed using a two-tailed t-test:

$$t = \frac{r\sqrt{n-2}}{\sqrt{1-r^2}}$$

We reject the null hypothesis (ρ = 0) at α = 0.05 when |t| exceeds the critical value, providing statistical evidence that the observed relationship is not due to chance.

Data Sources

Body Weight data was primarily collected using Fitbit. Fitbit makes activity tracking easy and automatic.

Sleep Efficiency data was primarily collected using Fitbit. Fitbit makes activity tracking easy and automatic.

Data Quality

Data quality measures were applied to ensure reliable results:

  • Minimum Data Requirement: Only participants with sufficient paired observations were included in the analysis.
  • Outlier Handling: Extreme values were winsorized to reduce the influence of measurement errors.
  • Missing Data: Days with missing values were handled using appropriate filling strategies based on the variable type.
  • Test User Exclusion: Test accounts and invalid users were excluded from all analyses.

Principal Investigator

Program & Methods

Mike P. Sinn
Sinn, M. P.

Designed and implemented data collection, aggregation, causal inference pipeline, and automated study generation framework. Developed the Predictor Impact Score methodology operationalizing Bradford Hill criteria for ranking causal relationships in observational data. When he tells people this at parties, they usually say they have to go check on their car.

Individual study outputs are automated, reproducible, and open to external audit. (Which I would seriously recommend.)

Contact

Cite This Study

APA Format
Sinn, M. P. (2026). Causal Analysis: Does Body Weight Affect Sleep Efficiency?. The Journal of Citizen Science. https://studies.crowdsourcingcures.org/study/cause-1486-effect-5211811-population-study
BibTeX 
@misc{sinn_cause_1486_effect_5211811_population_study_2026,
  author = {Sinn, Mike P.},
  title = {Causal Analysis: Does Body Weight Affect Sleep Efficiency?},
  year = {2026},
  publisher = {The Journal of Citizen Science},
  url = {https://studies.crowdsourcingcures.org/study/cause-1486-effect-5211811-population-study},
  note = {Accessed: January 11, 2026}
}
Chicago/Turabian
Sinn, Mike P. "Causal Analysis: Does Body Weight Affect Sleep Efficiency?." The Journal of Citizen Science. Accessed January 11, 2026. https://studies.crowdsourcingcures.org/study/cause-1486-effect-5211811-population-study.
Harvard
Sinn, M.P., 2026. Causal Analysis: Does Body Weight Affect Sleep Efficiency?. [Aggregated N-of-1 Study] The Journal of Citizen Science. Available at: https://studies.crowdsourcingcures.org/study/cause-1486-effect-5211811-population-study [Accessed January 11, 2026].

Study Type: Aggregated N-of-1 Observational Mega-Study
Evidence Level: Level II (Real-World Evidence)
Methodology: Bradford Hill Criteria with Predictor Impact Score (PIS)

References

This framework was originally developed in 2013 based on the Bradford Hill criteria. Subsequent literature has independently validated similar approaches to causal inference from observational data:

  1. Hill, A.B. (1965). The environment and disease: association or causation? Proceedings of the Royal Society of Medicine, 58(5), 295-300. [Bradford Hill criteria]
  2. Lillie, E.O., et al. (2011). The n-of-1 clinical trial: the ultimate strategy for individualizing medicine? Personalized Medicine, 8(2), 161-173. [N-of-1 methodology]
  3. Pearl, J. (2009). Causality: Models, Reasoning, and Inference . Cambridge University Press. [Causal inference]
  4. Hernán, M.A., & Robins, J.M. (2020). Causal Inference: What If . Chapman & Hall/CRC. [Free textbook]
  5. FDA (2018). Framework for FDA's Real-World Evidence Program . U.S. Food and Drug Administration. [Regulatory context]
  6. Duan, N., et al. (2013). Single-patient (n-of-1) trials: a pragmatic clinical decision methodology . Journal of Clinical Epidemiology, 66(8), S21-S28.
  7. Platt, R., et al. (2018). The FDA Sentinel Initiative—an evolving national resource . New England Journal of Medicine, 379(22), 2091-2093.

This information is for research and educational purposes only, not medical advice. Consult a healthcare provider before making health decisions. Terms of Service

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