EAL

EE: Room Conditions (2013)

Citation:

van Ooijen AMJ, van Marken Lichtenbelt WD, van Steenhoven AA, Westerterp KR. Seasonal changes in metabolic and temperature responses to cold air in humans. Physiology & Behavior. 2004; 82: 545-553.

Study Design:

Time Study

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate seasonal changes in response to mild cold
Hypothesis: Individual differences in cold response exist ranging from a more insulative vasomotor response to a more metabolic response to cold.
Definitions:
- “Steady state”
- “Resting metabolic rate”: Metabolic rate (kJ per minute) in a thermo-neutral environment, lying still and awake in a post-absorptive state
- “Sleeping metabolic rate”: The average metabolic rate during at least three hours of sleep with the lowest activity as registered by radar and usually between 3:00 and 6:00 p.m.
- “Average metabolic rate”: The sleeping metabolic rate and RMR
- “VO2 max”: The highest oxygen uptake averaged over 30 seconds
- “Maximal performance”: Forced ventilation, a leveling off of oxygen uptake or a respiratory quotient above 1.1
- “Acclimatization”
- “Insulative metabolic response.”

Inclusion Criteria:

Understand and give written consent
Non-smokers
No medications except birth control
Not extreme athletes but spending average time on sports or daily living activities.

Exclusion Criteria:

Refusal to consent
Not meeting inclusion criteria.

Description of Study Protocol:

Protocol

Summer measure in August and September and Winter measure in February and March
No drop-outs
Subjects stayed overnight and experiments followed in the morning
Body composition and max O₂ intake was taken within one week of the experiment.

Anthropometric

Height measured? Yes
Weight measured? Yes
Fat-free mass measured? Yes.

Clinical

Monitored heart rate? Yes
Body temperature? Yes.

Resting Energy Expenditure

IC type: Omnical with ventilated hood system
Equipment of calibration: Likely
Coefficient of variation using std gases: No
Rest before measure (state length of time rested if available): Overnight stay; 15 minutes
Measurement length: 60 minutes, but only using the last 45 minutes of each hour
Steady state: Not specified
Fasting length: 10 hours
Exercise restrictions XX hours prior to test? Yes
Room temp: 22° C
Number of measures within the measurement period: Continuous for 4 hours? (one hour at normal room temperature and three hours at cold temp)
Were some measures eliminated? Yes, the first 15 minutes
Were a set of measurements averaged? Yes
IF average, identify length of each measure and numbers of measurements? 45 minutes
Coefficient of variation in subjects measures? No
Training of measurer? Not specified but likely due to detailed description of measure procedures
Subject training of measuring process? Yes.

Dietary

Intervening factor: All but one female was on contraceptive medications or in pre-ovulatory phase of her menstrual cycle.

Data Collection Summary:

Outcome(s) and Other Measures

Measured REE [(VO₂, L per minute), VCO₂ (L per minute; ml per kg per minute), RQ, ventilation (L per minute)]
Core body temperature via rectal and intestinal measure
Shivering using electromyography
Independent variables:
- Weight
- Height
- Age
- BMI.

Description of Actual Data Sample:

Enrolled Sample

N=20; 10 male, 10 female
Age: 19 to 36 years
BMI: 17 to 32kg/m².

Final Sample

22 patients (17 males, five females) aged 46 to 71 years
Mean age: 61.0±1.6 STD error mean (SEM)
Mean BMI: 25.6kg/m² (±SEM not provided)
Range: 19.0 to 29.6.

Statistical Tests

Incremental area under the curve (AUCinc) was calculated by subtracting RMR (MR at 22°) from the total area under the curve (AUCtot). Means±SD; individual differences paired and unpaired T-tests; ANOVA for repeated measures.

Summary of Results:

Body Composition

Summer
	Males Mean±SD	Females Mean±SD
Age, years	27±6	25±3
Weight, kg	78.8±15.5^a	63.3±8.1
Height, m	1.82±0.04^a	1.67±0.07
Fat-free body mass, kg^a	65.5±8.9	45.4±4.8
Fat mass, kg	14.3±8.6	17.9±5.1
Winter
	Males Mean±SD	Females Mean±SD
Weight, kg	79.9±16.6^a	64.2±6.9
Fat-free body mass, kg^a	64.2±9.8	45.8±4.2
Fat mass, kg	15.7±8.9*	18.4±4.0

^a = P<0.05 between males and females
* = P<0.05 between summer and winter/

Males were significantly taller, heavier and had a higher fat-free mass (FFM; kg) than women
Fat mass ranged between 8.2% and 30.9%
Mean FFM remained unchanged and FM increased significantly in winter in males (1.5%; P<0.05); the same trend (non-significant) occurred in females.

Metabolic Variables

Summer
	Males Mean±SD	Females Mean±SD
RMR, kJ per minute	5.25±0.56^a	4.23±0.46
RMR, kcal per minute	1.26±0.13^a	1.01±0.11
Winter
	Males Mean±SD	Females Mean±SD
RMR, kJ per minute	5.24±0.58^a	4.26±0.51
RMR, kcal per minute	1.25±0.14^a	1.02±0.12

^a = P<0.05 between males and females

Inter-individual variation in RMR at 22° was mainly explained by variation in FFM in Summer and Winter (R²-0.84 and 0.81, respectively
After adjustment for body composition in multiple linear regression analysis, no significant gender differences in RMR were found. There were no significant differences between seasons in RMR or VO₂ max.

Room Temperature Changes

During T₁-T₃, no shivering was registered by EMG and by subject self-report.

Metabolic rate (MR)

RMR was significantly increased during cold exposure compare to baseline (ANOVA for repeated measurements, P<0.001). In summer, the average MR increased from 4.7kJ±0.7kJ per minute to 5.1kJ±0.8kJ per minute (T₃) [1.12kcal±0.17kcal and 1.2kcal±0.19kcal per minute] and in winter, MR increased from 4.7kj±0.7kJ per minute to 5.3kJ±0.9 kJ per minute [1.12kcal±0.17kcal and 1.3kcal±0.22kcal per minute]
On average, the increase was 7.0%±10.5% (P<0.05) in summer and 11.5%±9.1% (P<0.012) in winter, respectively.

Individual Changes

The metabolic response ranged from a decrease of 4% to an increase of 30% in winter and from a decrease of 12% to an increase of 24% in summer (T-test values at T₃ vs. T₀)
The amount of AUC increase was slightly but not significantly higher in winter compared to summer
In summer and winter, approximately two-thirds (70% and 65%) of the metabolic response of T₃ was reached at T₁
If only the three-hour response was considered (T₁ to T₃), a significant increase was seen in winter but not in summer (winter P<0.01, summer P=0.13).

Author Conclusion:

As stated by the author in body of report:

[Two studies] report that the magnitude of the cold response, and to a lesser extent, the relative contribution of the metabolic and insulative vasomotor response, depends on the duration and severity of the cold exposure, the medium, water or air and acclimatization.
Individual variation in cold response is observed by the inverse relation between the insulative and metabolic cold response and the type is subject-specific; three hours of cold exposure revealed an increase in metabolic rate of 7.0% in summer and 11.5% in winter
As a heat-loss restricting mechanism, all skin temperatures decreases significantly in response to the mild cold but the decreases was not significantly different between seasons (i.e., no insulative vasomotor response); thus, body heat debt was less during cold exposure in winter compared to summer meaning even in a moderate climate and modern society, cold acclimatization occurred.
In [another study of N=8] describing moderate or mild-cold conditions, shivering occurred. Our test conditions (air temperature and clothing) so that during cold exposure no shivering would take place. The study indicates that NST seems to be a candidate for increases in metabolic rate.
No change in RMR or VO₂ max was found between seasons, independent of correction for the change in body composition. Thus a change in cold response due to a change in physical fitness is excluded.

Funding Source:

University/Hospital:

Maastricht University, University of Technology (both Netherlands)

Reviewer Comments:

Strengths

Indirect calorimetry measurement protocol outlined with defined metabolic measuring points
No dropouts reported
AUC total cold-induced thermogenesis statistical approach used.

Generalizability/Weaknesses

Generalizability to healthy non-obese and obese adults residing in moderate oceanic climates; inability to generalize to some old and very old adults or ethnic U.S.-residing groups of Asian and Black
Measured VO₂ max to explain possible RMR changes related to activity changes/conditioning related to weather
An IC measurement definition not reported is steady state, although likely to have achieved with overnight stay
Questionable validity of indirect calorimeter.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
	1.	Was the research question clearly stated?	Yes
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	N/A
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	1.3.	Were the target population and setting specified?	N/A
	1.3.	Were the target population and setting specified?	N/A
	2.	Was the selection of study subjects/patients free from bias?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	N/A
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	N/A
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	N/A
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
	3.	Were study groups comparable?	N/A
3.	Were study groups comparable?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
	4.	Was method of handling withdrawals described?	Yes
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
	5.	Was blinding used to prevent introduction of bias?	No
5.	Was blinding used to prevent introduction of bias?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
	6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?	Yes
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
	7.	Were outcomes clearly defined and the measurements valid and reliable?	No
7.	Were outcomes clearly defined and the measurements valid and reliable?		No
	7.1.	Were primary and secondary endpoints described and relevant to the question?	N/A
	7.1.	Were primary and secondary endpoints described and relevant to the question?	N/A
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	N/A
	7.5.	Was the measurement of effect at an appropriate level of precision?	N/A
	7.5.	Was the measurement of effect at an appropriate level of precision?	N/A
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	N/A
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	N/A
	7.7.	Were the measurements conducted consistently across groups?	N/A
	7.7.	Were the measurements conducted consistently across groups?	N/A
	8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?	???
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		???
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	N/A
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	N/A
	8.2.	Were correct statistical tests used and assumptions of test not violated?	N/A
	8.2.	Were correct statistical tests used and assumptions of test not violated?	N/A
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	N/A
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	N/A
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
	9.	Are conclusions supported by results with biases and limitations taken into consideration?	???
9.	Are conclusions supported by results with biases and limitations taken into consideration?		???
	9.1.	Is there a discussion of findings?	N/A
	9.1.	Is there a discussion of findings?	N/A
	9.2.	Are biases and study limitations identified and discussed?	N/A
	9.2.	Are biases and study limitations identified and discussed?	N/A
	10.	Is bias due to study's funding or sponsorship unlikely?	???
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	N/A
	10.1.	Were sources of funding and investigators' affiliations described?	N/A
	10.2.	Was the study free from apparent conflict of interest?	N/A
	10.2.	Was the study free from apparent conflict of interest?	N/A