Higher Average Daily Outdoor Temperature Predicts Very Slightly Lower Blood Pressure (Systolic - Top Number) for Population

Higher Average Daily Outdoor Temperature Predicts Very Slightly Lower Blood Pressure (Systolic - Top Number) for Population

Contents

Variables

A
Average Daily Outdoor Temperature 107
A
Blood Pressure 897

Categories

A
Environment 564
A
Vital Signs 110

Tags

Low Confidence
Very Weak Effect Size
Negative Relationship
Population Study
cause image gauge image effect image
Participants reported a 1.5% average decrease in Blood Pressure (Systolic - Top Number) following above average Average Daily Outdoor Temperature.

Abstract

Blood Pressure (Systolic - Top Number) was generally 1% higher than average after an average of 65.4 degrees fahrenheit of Average Daily Outdoor Temperature over the previous 7 days.

Aggregated data from 1 study participants suggests with a LOW degree of confidence (p=0.223, 95% CI -2.977 to 2.931) that Average Daily Outdoor Temperature has a very weakly negative predictive relationship (R=-0.023) with Blood Pressure.

The highest quartile of Blood Pressure measurements were observed following an average 66.6 degrees fahrenheit Average Daily Outdoor Temperature.

The lowest quartile of Blood Pressure measurements were observed following an average 62.3 degrees fahrenheit of Average Daily Outdoor Temperature.

After an onset delay of 0 seconds, Blood Pressure is typically 1% higher than average over the 7 days following around 62.3 degrees fahrenheit of Average Daily Outdoor Temperature Average Daily Outdoor Temperature.

Keywords: Average Daily Outdoor Temperature, Blood Pressure, N-of-1 trials, real-world evidence, causal inference, observational study

Preliminary: Based on 1 participants. Results may change as more data is collected.

Results

Primary Findings

Analysis of 28 paired observations from 1 participants revealed a minimal reduction in Blood Pressure following above-average Average Daily Outdoor Temperature exposure.

-1.7%
Change from Baseline
Minimal effect on Blood Pressure
0.00
Predictor Impact Score
Insufficient evidence for causal relationship

Supporting Statistics

Low
Confidence
-0.023
Correlation (r)
p = 0.360
Significance
z = 0.80
Effect Magnitude
φ = 1.00
Temporality

What This Means

When participants had above-average Average Daily Outdoor Temperature:

  • Blood Pressure decreased by 1.7% on average
  • Temporal analysis supports Average Daily Outdoor Temperature 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 1 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 Average Daily Outdoor Temperature values associated with high and low Blood Pressure 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

Average Daily Outdoor Temperature Distribution

Blood Pressure Distribution

Relationship Analysis

Statistical Summary

Relationship Statistics

Property Value
Cause Variable Name Average Daily Outdoor Temperature
Effect Variable Name Blood Pressure (Systolic - Top Number)
Sinn Predictive Coefficient 0.0010943696947135
Confidence Level LOW
Confidence Interval 2.9537
Forward Pearson Predictive Coefficient -0.023
Critical T Value 1.701
Average Average Daily Outdoor Temperature Over Previous 7 days Before ABOVE Average Blood Pressure ( Systolic - Top Number) 66.6 degrees fahrenheit
Average Average Daily Outdoor Temperature Over Previous 7 days Before BELOW Average Blood Pressure ( Systolic - Top Number) 62.3 degrees fahrenheit
Duration of Action 7 days
Effect Size very weakly negative
Number of Paired Measurements 28
Optimal Pearson Product -0.009214413797374
P Value 0.22319
Statistical Significance 0.3599
Strength of Relationship 2.9537
Study Type population
Analysis Performed At 2026-01-04
Number of Participants 1

Average Daily Outdoor Temperature Info

Property Value
Variable Name Average Daily Outdoor Temperature
Aggregation Method MEAN
Analysis Performed At 2020-10-11
Duration of Action 7 days
Kurtosis 2.6039819469393
Maximum Allowed Value 134 degrees fahrenheit
Mean 63.749346093146 degrees fahrenheit
Median 64.281163531761 degrees fahrenheit
Minimum Allowed Value -87 degrees fahrenheit
Number of Aggregate Predictors 0
Number of Aggregate Outcomes 107
Number of Measurements 95016
Number of Measurements (including those generated by tagged, joined, or child variables) 22144
Public true
Onset Delay 0 seconds
Standard Deviation 7.7762207716368
Unit Degrees Fahrenheit
User Variables 658
Variable Category Environment
Variable ID 6038776
Variance 118.83499021982

Blood Pressure Info

Property Value
Variable Name Blood Pressure (Systolic - Top Number)
Aggregation Method MEAN
Analysis Performed At 2020-09-15
Duration of Action 7 days
Kurtosis 9.6485959987812
Maximum Allowed Value 100000 millimeters merc
Mean 4546.9564108281 millimeters merc
Median 4547.0725028058 millimeters merc
Minimum Allowed Value 1 millimeters merc
Number of Aggregate Predictors 780
Number of Aggregate Outcomes 117
Number of Measurements 8517
Number of Measurements (including those generated by tagged, joined, or child variables) 5176
Public true
Onset Delay 0 seconds
Standard Deviation 31.78039339699
Unit Millimeters Merc
User Variables 61
UPC 647679244474
Variable Category Vital Signs
Variable ID 1874
Variance 23939.264480794

Introduction

Background

Average Daily Outdoor Temperature (Environment) and Blood Pressure (Vital Signs) 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 Average Daily Outdoor Temperature affect Blood Pressure?

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 Average Daily Outdoor Temperature for maximizing Blood Pressure?

Study Objective

The objective of this study is to determine the nature of the relationship (if any) between Average Daily Outdoor Temperature and Blood Pressure. Additionally, we attempt to determine the Average Daily Outdoor Temperature values most likely to produce optimal Blood Pressure 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 1.7% reduction in Blood Pressure following above-average Average Daily Outdoor Temperature exposure. The Predictor Impact Score (PIS) of 0.00 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 Blood Pressure is not statistically significant at a 95% confidence interval. This suggests that the Average Daily Outdoor Temperature value may not have a significant influence on the Blood Pressure value, or that more data is needed to detect an effect.

After treatment, a 1.5% decrease (-2.25 millimeters merc) from the mean baseline 130 millimeters merc was observed. The relative standard deviation at baseline was 2.2%. The observed change was 0.79964 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: 1.078
Critical t-value: 1.701

Since t = 1.08 < 1.70, we cannot 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 Average Daily Outdoor Temperature might influence Blood Pressure.

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 Average Daily Outdoor Temperature 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 Average Daily Outdoor Temperature
  • Confirmation through prospective or randomized designs
  • Biological mechanisms underlying the observed effects

Conclusion

📊 Preliminary Findings: With 1 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 Average Daily Outdoor Temperature was associated with a 1.7% reduction in Blood Pressure—a minimal effect. The Predictor Impact Score of 0.00 indicates this relationship is requiring additional data before conclusions.

Bottom Line: Based on a PIS of 0.00 and a 1.7% 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 Average Daily Outdoor Temperature may influence Blood Pressure 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 1 participants. Thus, the study design is equivalent to the aggregation of 1 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 Average Daily Outdoor Temperature would produce an observable change in Blood Pressure.
  • Duration of Action: It was assumed that Average Daily Outdoor Temperature could produce an observable change in Blood Pressure for as much as 7 days after the stimulus event.

Statistical Methods

For each participant, we calculated the Pearson correlation coefficient between Average Daily Outdoor Temperature values and subsequent Blood Pressure 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

Average Daily Outdoor Temperature 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.

Blood Pressure data was primarily collected using Withings. Withings creates smart products and apps to take care of yourself and your loved ones in a new and easy way. Discover the Withings Pulse, Wi-Fi Body Scale, and Blood Pressure Monitor.

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 Average Daily Outdoor Temperature Affect Blood Pressure (Systolic - Top Number)?. The Journal of Citizen Science. https://studies.crowdsourcingcures.org/study/cause-6038776-effect-1874-population-study
BibTeX 
@misc{sinn_cause_6038776_effect_1874_population_study_2026,
  author = {Sinn, Mike P.},
  title = {Causal Analysis: Does Average Daily Outdoor Temperature Affect Blood Pressure (Systolic - Top Number)?},
  year = {2026},
  publisher = {The Journal of Citizen Science},
  url = {https://studies.crowdsourcingcures.org/study/cause-6038776-effect-1874-population-study},
  note = {Accessed: January 10, 2026}
}
Chicago/Turabian
Sinn, Mike P. "Causal Analysis: Does Average Daily Outdoor Temperature Affect Blood Pressure (Systolic - Top Number)?." The Journal of Citizen Science. Accessed January 10, 2026. https://studies.crowdsourcingcures.org/study/cause-6038776-effect-1874-population-study.
Harvard
Sinn, M.P., 2026. Causal Analysis: Does Average Daily Outdoor Temperature Affect Blood Pressure (Systolic - Top Number)?. [Aggregated N-of-1 Study] The Journal of Citizen Science. Available at: https://studies.crowdsourcingcures.org/study/cause-6038776-effect-1874-population-study [Accessed January 10, 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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