UK Biobank Data Dictionary Browser

Total Fields

Filtered

Participant Coverage Statistics

Baseline (Instance 0)

~502,000 participants

First Repeat (Instance 1)

~20,000 participants

Imaging Visit (Instance 2)

~100,000 participants

Repeat Imaging (Instance 3)

~50,000 participants

Data Coding Reference

Many UK Biobank fields use coded values. Common codings include:

Coding 9: Sex (1=Male, 0=Female)
Coding 19: ICD-10 Diagnoses
Coding 20: ICD-9 Diagnoses
Coding 3: OPCS-4 Procedure Codes
Coding 4: Drug/Treatment Codes
Coding 6: Self-reported Conditions

Field Relationships & Linkages

Temporal Data Collection Timeline

2006-2010

Baseline Assessment (Instance 0)

Initial recruitment of 502,000 participants

Core measurements, questionnaires, biological samples

2012-2013

First Repeat (Instance 1)

~20,000 participants reassessed

Repeat core measurements

2014+

Imaging Study (Instance 2)

100,000 participants scanned

Brain, cardiac, abdominal MRI; DXA; carotid ultrasound

2019+

Repeat Imaging (Instance 3)

~50,000 participants re-scanned

Longitudinal imaging data

Data Quality Indicators

Field Quality Metrics:

⚠️ Missingness: Percentage of participants with missing data
📊 Distribution: Check for outliers and data anomalies
🔄 Consistency: Agreement across instances/timepoints
✅ Validation: Cross-reference with linked health records

💡 Recommendation: Always check the Data tab in UK Biobank Showcase for:

Histograms and distributions
Summary statistics (mean, SD, range)
Participant counts per instance
Notes on data collection methods

Phenotype Groupings

🫀 Cardiovascular Phenotypes

Hypertension (Field 20002, code 1065)
Coronary artery disease (Field 20002, code 1075)
Myocardial infarction (ICD10: I21-I22)
Stroke (ICD10: I60-I64)

🧠 Neurological Phenotypes

Alzheimer's disease (ICD10: G30)
Parkinson's disease (ICD10: G20)
Multiple sclerosis (ICD10: G35)
Epilepsy (ICD10: G40)

🫁 Respiratory Phenotypes

Asthma (Field 20002, code 1111)
COPD (ICD10: J44)
Lung function (Fields 20150-20154)

UK Biobank Data Dictionary

Field Comparison

🔬 Advanced Research Tools