Developing a surveillance system of sub-county data: Finding suitable population thresholds for geographic...

Area of Science:

• Environmental public health
• Geographic information systems
• Biostatistics

Background:

• Standardized sub-county geographies are essential for comparable public health data over time and place.
• Existing geographic units may not provide sufficient resolution or stability for localized health outcome analysis.
• The National Environmental Public Health Tracking Program aimed to improve geographic comparability for environmental public health data.

Purpose of the Study:

• To develop and recommend standardized sub-county geographic aggregations for public health surveillance.
• To determine appropriate population thresholds for creating stable health outcome estimates at a sub-county level.
• To provide a methodology applicable for finer resolution geographic analysis of health data.

Main Methods:

• Calculated expected census tract-level counts for asthma emergency department visits and lung cancer.
• Aggregated census tracts based on various total population and sub-population thresholds.
• Examined data suppression and stability for different aggregation schemes.

Main Results:

• Recommended a total population threshold of 5,000 persons for common health outcome schemes.
• Recommended a total population threshold of 20,000 persons for rare health outcome schemes.
• Health outcomes with a median of 17.0 or more cases demonstrated stable estimates at the census tract level.

Conclusions:

• Generated recommendations for three useful sub-county geographies: census tract, common outcome aggregation, and rare outcome aggregation.
• The developed methodology enables the aggregation of geographic units to produce stable rates at a finer resolution.
• These standardized geographies enhance public health surveillance capabilities for environmental health outcomes.