What the Maps Tell Us: Initial Findings

Note: Although the Asthma Rates map includes data for some Clark County census tracts, these data should be interpreted with caution. The map is based on insurance claims records reported to the Oregon Health Care Quality Corporation, which collects insurance claims data for health plans operating in Oregon. Some of the participating health plans submit claims data for members living in Clark County, but many do not. For this reason the Clark County data are based on a limited population of Clark County residents and may not be representative of the entire population. The analysis of the maps in this series will therefore focus only on the portions of the region located in Oregon.

According to the Asthma Rates map, the census tracts with the highest rates of asthma (16.13%-25%) are scattered throughout the region, with the largest clusters concentrated in Multnomah County. The Multnomah County census tracts are located along US-30 in parts of the Forest Park/Linnton and St. Johns neighborhoods, in parts of outer east Portland and Gresham, and in areas along the Columbia River. In Clackamas County, the census tracts with the highest rates of asthma are located in and adjacent to Milwaukie and Oregon City, and in unincorporated areas in the center and eastern edge of the county. In Washington County, the census tracts with the highest rates of asthma are located in sections of Hillsboro, Forest Grove, Tualatin, King City, and Beaverton, as well as in a few unincorporated areas near these cities.
 
Areas of the region with the lowest asthma rates include several small census tracts located in parts of Portland’s Sunnyside, Mt. Tabor, Concordia, Hillsdale, Bridlemile, Homestead, Arlington Heights, and Sylvan Heights neighborhoods, as well as census tracts located in the southern portions of Oregon City, Tualatin, and Beaverton.

The Asthma Rates in Relationship to Percent Students Eligible for Free or Reduced Price Lunch, Freeways and Arterial Streets map explores the relationship between asthma rates and poverty as well as the relationship between asthma rates and the locations of major sources of air pollution from vehicle emissions. In some parts of the region, census tracts with higher rates of asthma tend to be located along freeways, but this pattern is not found consistently across the region. For example, in Multnomah County, higher rates of asthma are located along parts of I-5, particularly in north Portland, and along I-84 and I-205. But in Washington County, some of the lowest asthma rates are found in census tracts along US-26. This inconsistency suggests that while proximity to freeways may influence asthma rates, it is not the only determining factor.

The relationship between asthma rates and poverty – as measured by the percentage of students eligible for free and reduced price lunch – is more consistent. Most of the region’s higher poverty schools are located in census tracts with relatively high asthma rates (13.10% and higher). Exceptions to the pattern include several high poverty schools in Hillsboro, Portland, and one east of Boring that are located in census tracts with asthma rates below 13%.

The Asthma Rates in Relationship to Populations of Color, Freeways and Arterial Streets map shows a similar relationship between asthma rates and race. Across the region, the areas with the highest densities of populations of color also tend to have higher asthma rates. This pattern isn’t uniform, but it is fairly consistent across the Oregon portions of the region. One of the most visible exceptions to this pattern is in a few areas in and adjacent to Hillsboro, Beaverton, and Happy Valley, where there are high densities of populations of color in census tracts with relatively low asthma rates.

The patterns in this map series are consistent with national data showing racial and income disparities in asthma rates. Given the significant impact that asthma can have on the immediate and long-term health and quality of life of both children and adults, these disparities are an important health equity issue that our region will need to address.