Issues with Age-Adjustment in Chronic Disease Populations

For comparisons made across time or between population groups, age adjustment is often used to eliminate differences in crude rates that result from differences in the populations' age distributions. In HP2010, direct age adjustment to the 2000 standard population was used for age adjusted objectives. For HP2020, adjustment to the 2000 standard population will continue to be used to make comparisons across Healthy People tracking periods and between numerous Healthy People objectives. Moving forward, we are exploring use of additional age adjusted statistics using the age distribution of the specific chronic disease as the standard population for objectives that target persons with chronic diseases, e.g., diabetes, cancer, chronic kidney disease, arthritis, coronary heart disease, and hypertension. The age distribution of the population with chronic diseases tends to be older than the overall population. For example, in the case of hypertension control, age adjustment using the 2000 standard population results in a lower estimate than age adjustment using the population with hypertension, which could affect measures of health disparities and of progress toward attainment of HP targets. Presenting findings for age adjusted objectives using both the 2000 standard and the supplemental disease-specific standard could make HP2020 more useful to general audiences, including policy-makers and the public, as well as to the scientific community.