US middle-aged adults have experienced concerning declines in health and life expectancy since 2010.

To investigate which groups of middle-aged adults are at risk of poor health trajectories, identify predictors of unhealthy aging, and assess potential consequences on health care utilization, costs, and mortality after these adults age into older adulthood.

We used longitudinal survey data from the nationally representative, biennial Health and Retirement Study (HRS) to follow a representative sample of adults age 51 and older.

A total of 12,333 US community-dwelling respondents.

We estimated health trajectories from biennial self-reported health status and limitations in activities of daily living and instrumental activities of daily living. Predictors of health trajectories included sociodemographic, clinical, and health care characteristics. Consequences of poor health trajectories after age 65 included self-reported hospitalizations, out-of-pocket medical costs, and mortality.

We identified four distinct trajectories: “Healthy Agers” (14.2%), “Less Healthy Agers” (40.7%), “Unhealthy Agers, Low Baseline” (31.0%), and “Persistently Ill” (14.1%). Predictors of the “Persistently Ill” and “Unhealthy Agers, Low Baseline” trajectories included male gender, non-Hispanic Black race, and Hispanic ethnicity. Predictors of less healthy and unhealthy aging trajectories included ≤ high school education, income ≤ 250% of federal poverty level, smoking, obesity, and chronic diseases including diabetes, whereas continuous insurance coverage in ages 50–64, compared with intermittent or no insurance, was associated with lower odds of less healthy and unhealthy aging trajectories. After age 65, less healthy and unhealthy aging trajectories were associated with greater hospitalizations, out-of-pocket costs, and mortality compared with “Healthy Agers.”

The findings suggest that unhealthy aging trajectories may frequently be set prior to age 50. Policy interventions earlier in life, such as availability of consistent health insurance coverage in early and mid-life, may mitigate downstream poor health and health care outcomes in older adulthood.