National Health and Nutrition Examination Survey

2009-2010 Data Documentation, Codebook, and Frequencies

Caffeine & Caffeine Metabolites - Urine (CAFE_F)

Data File: CAFE_F.xpt

First Published: March 2014

Last Revised: NA

Component Description

Trace metals have been associated with adverse health effects in occupational studies or laboratory studies, but have not been monitored in general population groups.

This method is used to achieve rapid and accurate quantifications of multiple elements of toxicological and nutritional interest. The method is sensitive and rapid enough to screen urine specimens from subjects suspected to be exposed to a number of important toxic elements, or to evaluate environmental or other nonoccupationally exposure to these same elements.

Eligible Sample

Participants aged 6 years and older, who met the subsample requirements, were eligible.

Description of Laboratory Methodology

Urine specimens are processed, stored, and shipped to the Division of Environmental Health Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention for analysis. Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation on Laboratory Data file for detailed data processing and editing protocols.

Caffeine and 14 of its metabolites are quantified in urine by use of high performance liquid chromatography-electrospray ionization-tandem quadrupole mass spectrometry (HPLC-ESI-MS/MS) with stable isotope labeled internal standards. A 50-µL aliquot of urine is first diluted with 450 µL of water. 100 µL of the diluted urine is then combined with 120 µL of a 0.2 N NaOH solution containing stable isotope labeled internal standards. The mixture is allowed to incubate for at least 30 min at room temperature, facilitating the conversion of an unstable uracil metabolite into a more stable form. Samples are then acidified 30 µL of 2.0 N HCl and 250 µL of a 1:9 methanol/water solution containing 0.1% formic acid such that the matrix of the sample is similar to the starting mobile phase composition of the analysis step. Samples are then filtered and analyzed by HPLC-ESI-MS/MS in both positive and negative ionization modes. Quantitation is based on peak area ratios interpolated against an 11-point calibration curve derived from calibrators in synthetic urine

This is the first two year cycle that caffeine and caffeine metabolites were measured. Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Data Processing and Editing

Read the General Documentation on Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Description of Laboratory Methodology section above.

Laboratory Quality Assurance and Monitoring

The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

Analytic Notes

NHANES Survey Design:

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Demographic file contains: Status Variables providing core information on the survey participant including examination status, Recoded Demographic Variables including age, gender, race etc., and Interview and Examination Sample Weight Variables and Survey Design Variables. The Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Demographic, Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

Subsample Weights

Urinary caffeine and caffeine metabolites were measured in a one third subsample of persons 6 years and over. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data.

Variance Estimation

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Demographic Data File contains demographic and sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.

Links to NHANES Data Files

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier SEQN.

Detection Limits

The detection limits were constant for all of the caffeine measurements in the data set.

The variable named LBD__LC indicates whether the result was below the limit of detection. There are two values: “0,” and “1.” “0” means that the result was at or above the limit of detection. “1” indicates that the result was below the limit of detection. In cases where the result was below the limit of detection, the value for that variable is the detection limit divided by the square root of two.

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

References

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Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:: SEQN
SAS Label:: Respondent sequence number
English Text:: Respondent sequence number
Target:: Both males and females 6 YEARS - 150 YEARS

WTSC2YR - Two-year C subsample weights

Variable Name:: WTSC2YR
SAS Label:: Two-year C subsample weights
English Text:: Two-year C subsample weights
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0 to 413068.05064	Range of Values	2831	2831
.	Missing	0	2831

URXUCR - Creatinine, urine (mg/dL)

Variable Name:: URXUCR
SAS Label:: Creatinine, urine (mg/dL)
English Text:: Creatinine, urine (mg/dL)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
3 to 553	Range of Values	2762	2762
.	Missing	69	2831

URXMU1 - 1-methyluric acid (umol/L)

Variable Name:: URXMU1
SAS Label:: 1-methyluric acid (umol/L)
English Text:: 1-methyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.41 to 2200	Range of Values	2714	2714
.	Missing	117	2831

URDMU1LC - MU1 caffeine comment code

Variable Name:: URDMU1LC
SAS Label:: MU1 caffeine comment code
English Text:: MU1 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2714	2714
1	Below lower detection limit	0	2714
.	Missing	117	2831

URXMU2 - 3-methyluric acid (umol/L)

Variable Name:: URXMU2
SAS Label:: 3-methyluric acid (umol/L)
English Text:: 3-methyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.07 to 38.4	Range of Values	2714	2714
.	Missing	117	2831

URDMU2LC - MU2 caffeine comment code

Variable Name:: URDMU2LC
SAS Label:: MU2 caffeine comment code
English Text:: MU2 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2176	2176
1	Below lower detection limit	538	2714
.	Missing	117	2831

URXMU3 - 7-methyluric acid (umol/L)

Variable Name:: URXMU3
SAS Label:: 7-methyluric acid (umol/L)
English Text:: 7-methyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.07 to 678	Range of Values	2714	2714
.	Missing	117	2831

URDMU3LC - MU3 caffeine comment code

Variable Name:: URDMU3LC
SAS Label:: MU3 caffeine comment code
English Text:: MU3 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2679	2679
1	Below lower detection limit	35	2714
.	Missing	117	2831

URXMU4 - 1,3-dimethyluric acid (umol/L)

Variable Name:: URXMU4
SAS Label:: 1,3-dimethyluric acid (umol/L)
English Text:: 1,3-dimethyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 2020	Range of Values	2714	2714
.	Missing	117	2831

URDMU4LC - MU4 caffeine comment code

Variable Name:: URDMU4LC
SAS Label:: MU4 caffeine comment code
English Text:: MU4 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2628	2628
1	Below lower detection limit	86	2714
.	Missing	117	2831

URXMU5 - 1,7-dimethyluric acid (umol/L)

Variable Name:: URXMU5
SAS Label:: 1,7-dimethyluric acid (umol/L)
English Text:: 1,7-dimethyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 1230	Range of Values	2714	2714
.	Missing	117	2831

URDMU5LC - MU5 caffeine comment code

Variable Name:: URDMU5LC
SAS Label:: MU5 caffeine comment code
English Text:: MU5 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2633	2633
1	Below lower detection limit	81	2714
.	Missing	117	2831

URXMU6 - 3,7-dimethyluric acid (umol/L)

Variable Name:: URXMU6
SAS Label:: 3,7-dimethyluric acid (umol/L)
English Text:: 3,7-dimethyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 44.5	Range of Values	2714	2714
.	Missing	117	2831

URDMU6LC - MU6 caffeine comment code

Variable Name:: URDMU6LC
SAS Label:: MU6 caffeine comment code
English Text:: MU6 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2543	2543
1	Below lower detection limit	171	2714
.	Missing	117	2831

URXMU7 - 1,3,7-trimethyluric acid (umol/L)

Variable Name:: URXMU7
SAS Label:: 1,3,7-trimethyluric acid (umol/L)
English Text:: 1,3,7-trimethyluric acid (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 70.7	Range of Values	2714	2714
.	Missing	117	2831

URDMU7LC - MU7 caffeine comment code

Variable Name:: URDMU7LC
SAS Label:: MU7 caffeine comment code
English Text:: MU7 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2398	2398
1	Below lower detection limit	316	2714
.	Missing	117	2831

URXMX1 - 1-methylxanthine (umol/L)

Variable Name:: URXMX1
SAS Label:: 1-methylxanthine (umol/L)
English Text:: 1-methylxanthine (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 1400	Range of Values	2714	2714
.	Missing	117	2831

URDMX1LC - MX1 caffeine comment code

Variable Name:: URDMX1LC
SAS Label:: MX1 caffeine comment code
English Text:: MX1 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2714	2714
1	Below lower detection limit	0	2714
.	Missing	117	2831

URXMX2 - 3-methylxanthine (umol/L)

Variable Name:: URXMX2
SAS Label:: 3-methylxanthine (umol/L)
English Text:: 3-methylxanthine (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 830	Range of Values	2714	2714
.	Missing	117	2831

URDMX2LC - MX2 caffeine comment code

Variable Name:: URDMX2LC
SAS Label:: MX2 caffeine comment code
English Text:: MX2 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2697	2697
1	Below lower detection limit	17	2714
.	Missing	117	2831

URXMX3 - 7-methylxanthine (umol/L)

Variable Name:: URXMX3
SAS Label:: 7-methylxanthine (umol/L)
English Text:: 7-methylxanthine (umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 1610	Range of Values	2714	2714
.	Missing	117	2831

URDMX3LC - MX3 caffeine comment code

Variable Name:: URDMX3LC
SAS Label:: MX3 caffeine comment code
English Text:: MX3 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2708	2708
1	Below lower detection limit	6	2714
.	Missing	117	2831

URXMX4 - 1,3-dimethylxanthine(theophylline)umol/L

Variable Name:: URXMX4
SAS Label:: 1,3-dimethylxanthine(theophylline)umol/L
English Text:: 1,3-dimethylxanthine(theophylline)umol/L
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 338	Range of Values	2714	2714
.	Missing	117	2831

URDMX4LC - MX4 caffeine comment code

Variable Name:: URDMX4LC
SAS Label:: MX4 caffeine comment code
English Text:: MX4 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2518	2518
1	Below lower detection limit	196	2714
.	Missing	117	2831

URXMX5 - 1,7-dimethylxanthine(paraxanthine)umol/L

Variable Name:: URXMX5
SAS Label:: 1,7-dimethylxanthine(paraxanthine)umol/L
English Text:: 1,7-dimethylxanthine(paraxanthine)(umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.07 to 418	Range of Values	2714	2714
.	Missing	117	2831

URDMX5LC - MX5 caffeine comment code

Variable Name:: URDMX5LC
SAS Label:: MX5 caffeine comment code
English Text:: MX5 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2596	2596
1	Below lower detection limit	118	2714
.	Missing	117	2831

URXMX6 - 3,7-dimethylxanthine(theobromine)umol/L

Variable Name:: URXMX6
SAS Label:: 3,7-dimethylxanthine(theobromine)umol/L
English Text:: 3,7-dimethylxanthine(theobromine)(umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.04 to 482	Range of Values	2714	2714
.	Missing	117	2831

URDMX6LC - MX6 caffeine comment code

Variable Name:: URDMX6LC
SAS Label:: MX6 caffeine comment code
English Text:: MX6 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2687	2687
1	Below lower detection limit	27	2714
.	Missing	117	2831

URXMX7 - 1,3,7-trimethylxanthine(caffeine)umol/L

Variable Name:: URXMX7
SAS Label:: 1,3,7-trimethylxanthine(caffeine)umol/L
English Text:: 1,3,7-trimethylxanthine(caffeine)(umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.07 to 152	Range of Values	2714	2714
.	Missing	117	2831

URDMX7LC - MX7 caffeine comment code

Variable Name:: URDMX7LC
SAS Label:: MX7 caffeine comment code
English Text:: MX7 caffeine comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2463	2463
1	Below lower detection limit	251	2714
.	Missing	117	2831

URXAMU - AAMU Caffeine result (umol/L)

Variable Name:: URXAMU
SAS Label:: AAMU Caffeine result (umol/L)
English Text:: 5-acetylamino-6-amino-3-methyluracil(umol/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.07 to 1730	Range of Values	2714	2714
.	Missing	117	2831

URDAMULC - AAMU comment code

Variable Name:: URDAMULC
SAS Label:: AAMU comment code
English Text:: AAMU comment code
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative
0	At or above the detection limit	2647	2647
1	Below lower detection limit	67	2714
.	Missing	117	2831

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