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Researching county health disparities

A beginner’s guide to investigating differences in health between Texas counties with the tools already on Vellora, from first question to an honest write-up.

Seven steps

  1. Ask a question about places

    A health disparity is a preventable difference in health closely linked with social, economic and environmental disadvantage, including where people live [1]. County data can show where differences exist. Start with a question it can answer, about counties rather than people.

    For example: do Texas counties with more diagnosed high blood pressure also have higher heart disease death rates?

  2. Choose measures and check what they are

    For each measure, find out whether it is a modeled estimate or an observed count, its year, who it covers and whether it is age-adjusted. PLACES estimates are modeled from a national survey with census data [2], and CDC cautions that they cannot track change over time [3]. Age-adjusted rates remove differences that come only from age [4]; crude figures do not.

    Check a measure in the reading guide

  3. Look at the whole state first

    Map the measure in Explore. Note where values are high and low, how many counties are withheld, and whether the pattern follows obvious lines such as urban and rural areas or the border.

    Map high blood pressure

  4. Compare specific counties carefully

    Put two counties side by side in Compare. Read the confidence intervals before the point estimates: small counties have wide intervals, and a few points of difference may be within the uncertainty.

    Compare Harris and Hidalgo counties

  5. Test whether two measures move together

    On the Research page, choose two measures. Read the correlation, the number of counties left out, the adjusted p-value and the scatter plot. A correlation describes counties, not people, and does not show cause.

    High blood pressure and heart disease deaths

  6. Add context

    Differences in health often travel with differences in income and access to care. Look at poverty alongside a health measure, and check primary care shortage areas on the map. Context helps you describe a pattern; it still does not prove a cause.

    Poverty and diagnosed diabetes

  7. Write it up honestly

    Name the source, release and year of every figure, say whether it is modeled, observed or an association, and list what the data cannot show.

    Supported: “Across [n] Texas counties, estimated high blood pressure prevalence (CDC PLACES, 2025 release) and heart disease death rates (CDC, 2022–2024) were [positively / negatively / not clearly] correlated (Spearman ρ = [value]).”

    Not supported: “High blood pressure causes the higher death rates in these counties,” or “people in this county are at higher risk.”

    Cite sources and limits from Methodology

Sources

  1. [1] NCI Dictionary of Cancer Terms: health disparity. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/health-disparity (accessed 2026-10-22).
  2. [2] PLACES: Methodology. Centers for Disease Control and Prevention. https://www.cdc.gov/places/methodology/index.html (accessed 2026-10-22).
  3. [3] PLACES: Frequently Asked Questions. Centers for Disease Control and Prevention. https://www.cdc.gov/places/faqs/index.html (accessed 2026-10-18).
  4. [4] Age adjustment (Health, United States: Sources and Definitions). CDC National Center for Health Statistics. https://www.cdc.gov/nchs/hus/sources-definitions/age-adjustment.htm (accessed 2026-10-22).
County patterns describe populations, not individuals. Vellora provides general education and research tools, not medical advice.