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Praxis Data Lab · Variable History

Variable history and harmonization report.

Review variable definitions, cycle chronology, survey design, laboratory methods, method-change boundaries, detection limits, and evidence-backed harmonization actions.

1matching variable codes

12 release records across 12 datasets and 12 cycles.

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Search scope

Results for “BMXBMI”

Harmonization summary

1 label-stable codes

Label changes detected
0
Multiple dataset contexts
0
Unique codes
1
Enriched codes in this report
1

Scientific safeguard

Qualified assessment is authoritative; chronology remains supporting evidence.

Praxis separates source-stated method or instrument changes from automated differences in CDC/NCHS method text. The qualified harmonization assessment below is the researcher-facing conclusion; method chronology explains the underlying evidence and does not override that adjudication.

Variable-by-variable chronology

Qualified harmonization assessment and indexed evidence

Each variable first shows the current qualified assessment used by Study Builder, followed by cycle-specific source evidence and method chronology.

BMXBMICompatible

Body Mass Index (kg/m**2)

Observed years
1999–2023
Release records
12
Datasets
12
Components
Examination
Qualified Praxis harmonization assessment

Compatible · high confidence

CDC/NCHS documentation supports continuity of the core NHANES anthropometry protocol across Continuous NHANES. BMI remains the derived construct of weight in kilograms divided by standing height in meters squared. Indexed differences for this variable are limited to dataset context and documentation wording, not a confirmed measurement or calculation discontinuity.

Evidence provenance: CDC/NCHS source-confirmed evidence · Praxis deterministic adjudication

Praxis harmonization actions
  • Pool BMI across calibrated cycles without a method adjustment when no substantive variable-level change is present. Continue to apply cycle-appropriate NHANES weights, eligibility restrictions, and ordinary analytic guidance.
Supporting CDC/NCHS evidence
Supporting source-evidence notes

Method documentation varies across releases. Praxis flags the affected boundaries for review without automatically calling them scientific method changes.

These notes summarize indexed evidence and method-text signals. They do not supersede the qualified harmonization assessment above.

Documented weight variables
No explicit weight captured
Units observed
Not stated / categorical
Enriched releases
12
Method-change status
documentation varies
Method-change assessment

Method documentation varies across cycles

Method documentation or comparability language varies across releases, but Praxis has not confirmed a substantive method change from the captured text alone. Review the flagged boundaries before pooling.

Releases with method evidence
12
Flagged method boundaries
11
Assessment status
Method documentation varies across cycles
Inference rule
Documentation differences ≠ confirmed method changes
Method / instrument change points and harmonization actions
  • 1999-2000 → 2001-2002: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2001-2002 → 2003-2004: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2003-2004 → 2005-2006: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2005-2006 → 2007-2008: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2007-2008 → 2009-2010: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2009-2010 → 2011-2012: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2011-2012 → 2013-2014: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2013-2014 → 2015-2016: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2015-2016 → 2017-2018: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2017-2018 → 2017-2020: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
  • 2017-2020 → 2021-2023: Documentation changed — method change not yet confirmed · Evidence: automated documentation comparison. The captured CDC/NCHS method documentation differs from the preceding enriched release. Praxis does not treat a text difference alone as proof that the scientific method changed.
    Harmonization action: Review the linked source documents before pooling across this boundary. Until a substantive method/instrument change is confirmed, classify this as documentation variation rather than a scientific discontinuity. Review source
Cycle-by-cycle method chronology
  • 1999-2000: BMX — Data Collection Methods The data collection methods, examination protocol, and data collection forms are fully documented in the Anthropometry Procedures Manual. Examination Protocol See Item 3 above. In addition, for general guidelines on standard procedures that were followed for the anthropometric measures, refer to the Anthropometric Standardization Reference manual (Lohman, 1988). For specific guidelines, the Anthropometric Procedures Video that demonstrates the NHANES III anthropometric p…
  • 2001-2002: BMX_B — The data collection methods, examination protocol, and data collection forms are fully documented in the NHANES Anthropometry Procedures Manual. In addition, for general guidelines on standard procedures that were followed for the anthropometric measures, please refer to the Anthropometric Standardization Reference Manual (Lohman, 1988). The actual measurement techniques used in the survey are illustrated in the NHANES III Anthropometric Procedures Video. The video demonstrates the NHANES III a…
  • 2003-2004: BMX_C — The body measurement assessments performed on survey participants varied according to the age of the survey participant. The body measurement protocol used age at the time of the screening interview. In some instances, several weeks elapsed between the initial screening interview and the health examination visit. The Demographics Data File includes an age variable for age at examination (RIDAGEEX). Arm and leg measurements were made on the right side of the body. If an examinee had an amputatio…
  • 2005-2006: BMX_D — The body measurement data were collected by trained health technicians. The health technician was accompanied by a recorder during each body measurement examination. The respondent’s age, at the time of the screening interview, determined the body measurement examination protocol for survey participants. In some instances, several weeks elapsed between the initial screening interview and the health examination. The Demographics data file includes variables for age at screening (RIDAGEYR and RID…
  • 2007-2008: BMX_E — The body measurement data were collected by trained health technicians. The health technician was assisted by a recorder during the body measurement examination. The respondent’s age at the time of the screening interview determined the body measurement examination protocol for survey participants. In some instances the age at screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables for age at screening (RIDAGEYR …
  • 2009-2010: BMX_F — The body measurement data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measurement examination. The respondent’s age at the time of the screening interview determined the body measurement examination protocol for survey participants. In some instances the age at screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes …
  • 2011-2012: BMX_G — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables for age in years …
  • 2013-2014: BMX_H — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables for age in years …
  • 2015-2016: BMX_I — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables for age in years …
  • 2017-2018: BMX_J — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables for age in years …
  • 2017-2020: P_BMX — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables age in years at s…
  • 2021-2023: BMX_L — The body measures data were collected, in the Mobile Examination Center (MEC), by trained health technicians. The health technician was assisted by a recorder during the body measures examination. The participant’s age at the time of the screening interview determined the body measures examination protocol. In some instances, the age at the screening interview and age at the time of the health examination differed by several weeks. The Demographics data file includes variables age in years at s…
Praxis-enriched cycle evidence
  • 1999-2000: BMX · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2001-2002: BMX_B · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2003-2004: BMX_C · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2005-2006: BMX_D · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2007-2008: BMX_E · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2009-2010: BMX_F · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2011-2012: BMX_G · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2013-2014: BMX_H · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2015-2016: BMX_I · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2017-2018: BMX_J · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2017-2020: P_BMX · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
  • 2021-2023: BMX_L · Target: Both males and females 2 YEARS - 150 YEARS · Method evidence captured
Variable names / labels over time
  • Body Mass Index (kg/m**2) — 1999-2000 · 2001-2002 · 2003-2004 · 2005-2006 · 2007-2008 · 2009-2010 · 2011-2012 · 2013-2014 · 2015-2016 · 2017-2018 · 2017-2020 · 2021-2023
Cycle-by-cycle release history