Bioelectrical Impedance Analysis and Vasoconstriction

Taylor GuffeyLauren MorganHarry HanShelby HassbergerDaniel KimElizabeth MorrisRachel PatelRadu Reit

Problem Statement & Purpose

• Develop a hypothesis in which we test a factor, other than misuse and malfunction, that affects the analysis of body fat percentage.

• The purpose of this study is to evaluate whether the temperature of the room can affect the body fat percentage reading for an individual.

Hypothesis Groundwork

• Buono study finds ambient air temperature affects BF% reading– 20°C difference1

– Why air temperature?• Deghan study concludes vasodilation decreases BF%

reading2

– Increase in skin temperature• Therefore, vasoconstriction increases BF% reading– Decrease in ambient air temperature to decrease skin

temperature

Hypothesis

Null Hypothesis• There will be no difference in the readings of body

fat percentage from 24oC to 4oC as measured by the bioelectrical impedance analysis.

Alternative Hypothesis • There will be a statistically significant increase in

body fat percentage readings from 24oC to 4oC as measured by the bioelectrical impedance analysis.

Pilot Study

• Follows trend suggested by Deghan

0 100 200 300 400 500 600 70018

18.5

19

19.5

20

20.5

21

21.5

22

f(x) = − 0.0000035751285751 x² + 0.0059221334221 x + 19.364735264735R² = 0.976529027813804

Mean Body Fat % Vs. Time Af -ter Immediate 20°C

Time(s)

BF %

MeanHot Room 19.3Cold Room 21.6

Standard DeviationHot Room 4.274Cold Room 3.511

T-score1.96

Sample Size• Sample size derived from pilot study

• 23 estimated for statistical significance

• 24 used in experiment– Error with input of subject A1 data

Materials/Methodology• 2 groups, 12 subjects each• 24°C hot room (PBL room

in Whitaker)– BIA readings=Control

• Space heater to maintain hot room temperature

• 4°C cold room (in IBB)• Thermometer used to

monitor room temperature

•Read and sign consent form•Given Instruction sheet•Assigned alphanumeric ID on name tag•Given Data card with corresponding ID•Offered a jacket for experiment (both rooms)

Materials/Methodology• Clock to record time of

subject’s entry• Height taken with meter

stick• Weight taken with spring

scale• Survey given to determine

ineligible subjects• Omron HBF-360 Fat

Analyzer to measure body fat % of subject

http://image3.examiner.com/images/blog/wysiwyg/image/omron_HBF-306.jpg

Methodology

• Two groups– A1-12 and B1-12

• Time limited to 3 hours• 38 minutes per trial– 2 trials

• Subjects enter hot room 30 seconds apart• Last 2 subjects enter 1 minutes apart

Height

Survey & Time Table

Weight

Heater

BIA Reading Station

Chair

Door

Waiting Area

Warm Room 24oC

Time & BIA Reading Station

Door

Waiting Area

Ten Minutes Later Ten Minutes Later

Simulation

Cold Room 4oC

DataSubjects Height Weight (lbs) Gender Age Hot BIA Cold BIA

A1 5’10” 6' 2" 184 Male 19 13.5 17.35A2 5' 8.5" 148 Male 18 15.9 17.65A3 5' 2" 137 Female 19 26.35 27.55A4 5' 11" 179 Male 19 16.65 16.7A5 5' 5" 141 Female 19 29.7 30.5A6 5' 8" 165 Male 20 18.25 19.05A7 5' 9.75" 166 Male 19 17.25 18.25A8 5' 4.75" 139 Female 18 25.1 26.35A9 5' 8.25" 135 Female 19 17.7 18.7

A10 5' 8" 155 Male 19 15.9 17.25A11 6' 0" 164 Male 18 13.2 15.6A12 5' 11.5" 182 Male 19 19.45 20.6B1 6' 2" 166 Male 19 11.95 13.65B2 5' 5.25" 148 Female 19 29.15 29.3B3 5' 10" 151 Male 19 7.5 9.85B4 6' 4" 211 Male 20 13.95 14.6B5 5' 10.75" 153 Male 18 14.7 16.95B6 6' 1" 186 Male 18 18.05 18.9B7 6' 2" 163 Male 18 13.7 14.4B8 5' 10" 170 Male 20 11.3 13.1B9 6' 0" 175 Female 19 24.5 25.6

B10 5' 11.75" 138 Male 19 9.65 11.05B11 6' 1.5" 171 Male 19 10.35 11.75B12 5' 10.5" 195 Male 19 18.6 19.95

T-Score Calculation

XD = Mean of the differencesSD = Standard Deviation of the differencesn = Sample sizeμ0=Population mean

€

t =X D − μ0SDn

= (X D −0)⋅nSD

= (1.237 −0)⋅ 230.617

= 9.608

Statistical Analysis

Statisticst-score 9.608p-value 1.2423E-09

Standard Deviation 0.617402438

Mean of Difference 1.237

•Student’s Matched-Paired One-Tailed T-test

•Null Hypothesis is rejected• p < .05

Analysis

-1 -0.5 0 0.5 1 1.5 20

0.5

1

1.5

2

2.5

3

3.5Distribution of the Mean of Differences in BF% Readings

Norm Dist of ExperimentNorm Dist of No Sig. Diff.

BF% Differences

Normal Density

1.237

Outliers

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8BF% Difference

Q1 Q2 Q3

Discussion

• Null hypothesis is rejected

• Statistically significant increase in BIA readings– Average increase in BF% reading by 1.237%

• Data supports the alternative hypothesis

Improvements

• Smaller sample size

– Small p-value

• Multiple devices per room

– (same device used on subject throughout)

References1Buono, M. J., Burke, S., Endemann, S., Graham, H., Gressard, C., Griswold, L.,

et al. (2004). The effect of ambient air temperature on whole-body bioelectrical impedance. Physiological Measurement, 25(1), 119-123.

2Dehghan, M., & Merchant, A. (2008). Is bioelectrical impedance accurate for use in large epidemiological studies? Nutrition Journal, 7(1), 26.

Questions?