Higher Body Weight Predicts Moderately Lower Brain Fog (difficulty Thinking Clearly) for Population

Higher Body Weight Predicts Moderately Lower Brain Fog (difficulty Thinking Clearly) for Population

Contents

Variables

A
Body Weight 1140
A
Brain Fog (Difficulty Thinking Clearly) 379

Categories

A
Physique 41
A
Symptoms 13336

Tags

Low Confidence
Moderate Effect Size
Negative Relationship
Population Study
cause image gauge image effect image
Participants reported a 7.4% average decrease in Brain Fog (difficulty Thinking Clearly) following above average Body Weight.

Abstract

Brain Fog (difficulty Thinking Clearly) was generally 3.8% lower than average after 159 pounds of Body Weight per 7 days.

Aggregated data from 2 study participants suggests with a LOW degree of confidence (p=0.189, 95% CI -0.709 to -0.179) that Body Weight has a moderately negative predictive relationship (R=-0.444) with Brain Fog.

The highest quartile of Brain Fog measurements were observed following an average 159 pounds Body Weight.

The lowest quartile of Brain Fog measurements were observed following an average 159 pounds of Body Weight.

After an onset delay of 0 seconds, Brain Fog is typically 4% lower than average over the 7 days following around 159 pounds of Body Weight Body Weight.

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

Preliminary: Based on 2 participants. Results may change as more data is collected.

Results

Primary Findings

Analysis of 21 paired observations from 2 participants revealed a minimal reduction in Brain Fog following above-average Body Weight exposure.

-3.8%
Change from Baseline
Minimal effect on Brain Fog
0.08
Predictor Impact Score
Insufficient evidence for causal relationship

Supporting Statistics

Low
Confidence
-0.444
Correlation (r)
p = 0.071
Significance
z = 0.66
Effect Magnitude
φ = 1.00
Temporality

What This Means

When participants had above-average Body Weight:

  • Brain Fog decreased by 3.8% on average
  • 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. With only 2 participants, these scores are preliminary and will become more reliable as additional data is collected.

Optimal Daily Values

No clear dose-response relationship detected. The Body Weight values associated with high and low Brain Fog 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. With more participants, a clearer pattern may emerge.

Population Correlation

Body Weight Distribution

Brain Fog Distribution

Statistical Summary

Relationship Statistics

Property Value
Cause Variable Name Body Weight
Effect Variable Name Brain Fog (difficulty Thinking Clearly)
Sinn Predictive Coefficient 0.080556055596766
Confidence Level LOW
Confidence Interval 0.26497
Forward Pearson Predictive Coefficient -0.4444
Critical T Value 1.74
Average Body Weight Over Previous 7 days Before ABOVE Average Brain Fog (difficulty Thinking Clearly) 159 pounds
Average Body Weight Over Previous 7 days Before BELOW Average Brain Fog (difficulty Thinking Clearly) 159 pounds
Duration of Action 7 days
Effect Size moderately negative
Number of Paired Measurements 21
Optimal Pearson Product 0.78370140976123
P Value 0.18869
Statistical Significance 0.0713
Strength of Relationship 0.26497
Study Type population
Analysis Performed At 2026-01-04
Number of Participants 2

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

Brain Fog (Difficulty Thinking Clearly) Info

Property Value
Variable Name Brain Fog (difficulty Thinking Clearly)
Aggregation Method MEAN
Analysis Performed At 2020-10-11
Duration of Action 24 hours
Kurtosis 1.5439155850678
Maximum Allowed Value 5 out of 5
Mean 3.4220148648649 out of 5
Median 3.415627027027 out of 5
Minimum Allowed Value 1 out of 5
Number of Aggregate Predictors 307
Number of Aggregate Outcomes 72
Number of Measurements 506
Number of Measurements (including those generated by tagged, joined, or child variables) 506
Public true
Onset Delay 0 seconds
Standard Deviation 0.4041311973139
Unit 1 to 5 Rating
User Variables 106
UPC 0
Variable Category Symptoms
Variable ID 88305
Variance 0.40201953169415

Introduction

Background

Body Weight (Physique) and Brain Fog (Symptoms) 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 Brain Fog?

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 Brain Fog?

Study Objective

The objective of this study is to determine the nature of the relationship (if any) between Body Weight and Brain Fog. Additionally, we attempt to determine the Body Weight values most likely to produce optimal Brain Fog 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 3.8% reduction in Brain Fog following above-average Body Weight exposure. The Predictor Impact Score (PIS) of 0.08 indicates insufficient evidence for a causal relationship.

Statistical Significance

Using a two-tailed t-test with alpha = 0.05, it was determined that the change in Brain Fog is statistically significant at a 95% confidence interval. The p-value of 0.0713 indicates there is less than a 7.13% probability that this result occurred by chance.

After treatment, a 7.4% decrease (-0.162 out of 5) from the mean baseline 2.84 out of 5 was observed. The relative standard deviation at baseline was 15.95%. The observed change was 0.65658 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: 2.442
Critical t-value: 1.740

Since t = 2.44 > 1.74, 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.

Community feedback on the biological plausibility of this relationship is still being collected. Consider the known mechanisms by which Body Weight might influence Brain Fog.

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

📊 Preliminary Findings: With 2 participants, these results are based on limited data. Effect sizes and confidence will improve as more participants contribute data. Consider these findings directional rather than definitive.

Above-average Body Weight was associated with a 3.8% reduction in Brain Fog—a minimal effect. The Predictor Impact Score of 0.08 indicates this relationship is requiring additional data before conclusions.

Bottom Line: Based on a PIS of 0.08 and a 3.8% effect size, this relationship currently lacks sufficient evidence. Continue monitoring as more data becomes available. Note: These conclusions may strengthen or change direction as more data is collected.

These findings contribute to our understanding of how Body Weight may influence Brain Fog in real-world conditions. While preliminary, these results may inform future research directions. As more participants contribute data, the reliability and precision of these findings will improve substantially.

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Methods

Study Design

This study is based on data donated by 2 participants. Thus, the study design is equivalent to the aggregation of 2 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 Brain Fog.
  • Duration of Action: It was assumed that Body Weight could produce an observable change in Brain Fog 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 Brain Fog 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.

Brain Fog data was primarily collected using QuantiModo. QuantiModo allows you to easily track mood, symptoms, or any outcome you want to optimize in a fraction of a second. You can also import your data from over 30 other apps and devices. QuantiModo then analyzes your data to identify which hidden factors are most likely to be influencing your mood or symptoms.

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 Brain Fog (difficulty Thinking Clearly)?. The Journal of Citizen Science. https://studies.crowdsourcingcures.org/study/cause-1486-effect-88305-population-study
BibTeX 
@misc{sinn_cause_1486_effect_88305_population_study_2026,
  author = {Sinn, Mike P.},
  title = {Causal Analysis: Does Body Weight Affect Brain Fog (difficulty Thinking Clearly)?},
  year = {2026},
  publisher = {The Journal of Citizen Science},
  url = {https://studies.crowdsourcingcures.org/study/cause-1486-effect-88305-population-study},
  note = {Accessed: January 11, 2026}
}
Chicago/Turabian
Sinn, Mike P. "Causal Analysis: Does Body Weight Affect Brain Fog (difficulty Thinking Clearly)?." The Journal of Citizen Science. Accessed January 11, 2026. https://studies.crowdsourcingcures.org/study/cause-1486-effect-88305-population-study.
Harvard
Sinn, M.P., 2026. Causal Analysis: Does Body Weight Affect Brain Fog (difficulty Thinking Clearly)?. [Aggregated N-of-1 Study] The Journal of Citizen Science. Available at: https://studies.crowdsourcingcures.org/study/cause-1486-effect-88305-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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