Health Status of Young Adults with Insurance Coverage Before and After Affordable Care Act Passage


Gelliza B Gervacio, MPH1,2; Margo Sidell, ScD, MSPH1; Xia Li, MS1; Deborah R Young, PhD, MBA1;
Michael Batech, DrPH3; Lei Qian, PhD1; Kristi Reynolds, PhD, MPH1; Corinna Koebnick, PhD1

Perm J 2019;23:17-223 [Full Citation]
E-pub: 03/18/2019


Introduction: The purpose of this study was to assess changes in health status of California young adults with insurance coverage before and after passage of the Affordable Care Act (ACA).
Methods: For this cross-sectional descriptive study, electronic health record information for young adults between ages 18 and 25 years enrolled in a large Southern California Health Plan in 2008, 2010, or 2015 was obtained (N = 665,686). Absolute changes and standardized annual differences in demographics and age-sex-race standardized prevalence of Elixhauser health conditions for pre-ACA (2008-2010) and post-ACA (2010-2015) periods were calculated.
Results: The number of young adults enrolled in the Health Plan increased by 145,000 (65%) during the ACA transition with a shift toward low-income young adults. The increase in high-deductible insurance plans observed pre-ACA stabilized with a standardized annual difference of 0.22 pre-ACA vs 0.05 post-ACA. The prevalences of obesity and other health conditions between pre-ACA and post-ACA periods essentially were unaltered and comparable between young adults who became new members (< 1 year) and those with long-term memberships (≥ 3 years).
Conclusion: In this California health care system, the health status of new young adult members was comparable to that of long-term members. Future research should assess whether these young adults retain their health insurance coverage after turning age 26 years and being removed from their parents’ insurance plans.


More Americans have had access to health care since passage of the Affordable Care Act (ACA) in 2010.1 Young adults in particular benefited from the ACA through the option to stay on their parents’ health plans until age 26 years and Medicaid expansions.2 Health insurance helps young adults gain access to preventive health services and manage financially in the event of a catastrophic illness or accident. Rising insurance rates for young adults are designed to reflect the societal benefits associated with including young adults in the insurance pool to help pay for costs incurred by older adults. However, new health insurance enrollees without previous coverage may have had limited or inconsistent access to screening or other preventive services and be unaware of their preexisting conditions or health risks. A 2015 study indicated that newly enrolled Medicaid populations may have more involved initial health care needs than others and higher long-term health care resource use after receiving increased benefit coverage.3 There is a paucity of knowledge regarding health status changes among young adults who have obtained insurance coverage since ACA passage, however. Most reports describe the general adult population, but research focusing on young adults is necessary because they differ from older adults with regard to health status.

The aim of this study was to evaluate if the ACA extended coverage for young adults in a large Health Plan in Southern California between pre- and post-ACA periods and if the newly enrolled young adults differed in their Health Status from those with longer enrollment.


Study Setting and Population

Kaiser Permanente Southern California (KPSC) is an integrated health care system that provided comprehensive health care for about 4.1 million Southern California residents in 2015.4 Members receive care in 14 hospitals and more than 220 medical offices owned by KPSC in 10 Southern California counties. Members enroll through their employer or the employer of a family member, individual prepaid plans, or state or federal programs such as Medicaid (Medi-Cal in California) and Medicare. In 2010, approximately 16% of the population in the coverage area received care from KPSC. The demographic distribution of KPSC membership largely reflects the distribution of the underlying census reference population.5 Clinical care information is captured using an electronic health record system. All administrative and clinical data are linked through a unique medical record number and include membership information, medical encounters, and other health care information. For this study, we identified all young adults (N = 665,686) between age 18 and 25 years who were enrolled in a KPSC Health Plan for the entire year, allowing a coverage gap of up to 45 days in 2008, 2010, or 2015. The study protocol was reviewed and approved by the KPSC institutional review board.

Demographic Information

All demographic data, including age, sex, and race/ethnicity, were retrieved from administrative records and the electronic health record. Race/ethnicity was obtained from self-report during enrollment into the Health Plan, during a health care encounter, or from birth certificates (if applicable). Young adults were categorized as non-Hispanic white, Hispanic, African American, Asian, Pacific Islander, Other, and Unknown. The “Other” race category included young adults who identified themselves as belonging to another racial/ethnic group or multiple races. If race information was not available, the individual was classified as “Unknown” race.6

Median household income and education in the patient’s residential census tract were used as area-based measures of socioeconomic status.7,8 Census-tract household income was classified according to an individual’s likelihood of having a household income lower than $15,000; $15,000 to $49,999; $50,000 to $74,999; $75,000 to $99,999; $100,000 to $149,999; or $150,000 or more. Neighborhood education was categorized according to an individual’s likelihood of having an education level of less than high school, high school graduate, some college or an associate’s degree, bachelor’s degree, or graduate or professional degree.

Insurance coverage obtained through government health care assistance programs such as Medi-Cal was used as an additional proxy with which to indicate socioeconomic status. Health insurance type was classified according to payer status as a state-subsidized health plan (including Medi-Cal), Medicare, commercial or self-funded health plan, or private insurance and deductible type (high-deductible or traditional health plan).9

Health Conditions and Elixhauser Comorbidity Score

The Elixhauser comorbidity score involves the diagnoses of 30 health conditions that likely influence hospital mortality. Because of the wide range of health conditions included, the Elixhauser comorbidity score is used as a measure of health in populations of all ages, but particularly for young adults.10,11 For this study, diagnoses for 29 of 30 health conditions, including hypertension, AIDS/HIV, and metastatic cancer, were obtained from the electronic health record by dichotomizing respective International Classification of Diseases-9 codes before October 1, 2015, and subsequent International Classification of Diseases-10 codes. Any conditions with a prevalence rate lower than 1% were removed from the results with the exception of conditions that particularly are relevant to young adults. These conditions were not reported: Anemia (blood loss), cardiac arrhythmia, congestive heart failure, coagulopathy, liver disease, lymphoma, metastatic cancer, other neurologic diseases, paralysis, peripheral vascular disease, pulmonary circulation disorder, renal failure, rheumatoid arthritis, solid tumor without metastasis, peptic ulcer disease, and valvular disease.

Statistical Analysis

For this descriptive study, the characteristics of the study population and the prevalence of overweight and obesity classes by demographic characteristics were compared during 2 time periods: 2008 to 2010 (pre-ACA) and 2010 to 2015 (post-ACA). The absolute differences (95% confidence intervals) were calculated for pre-ACA and post-ACA periods. Comparing the rate of change pre-ACA and post-ACA allowed us to determine ACA-related changes rather than secular trends. Because the absolute numbers of members are continuously changing, we used standardized differences to compare changes during the pre-ACA and post-ACA periods. Standardized differences provide a measure of effect size and allow comparison of changes during the pre-ACA (2008-2010) and post-ACA (2010-2015) periods. This scoring method is independent of sample size and is calculated as the difference in proportions divided by the pooled standard deviation. A standardized difference exceeding 0.20 generally is considered a relevant change.12

To control for possible confounding, health condition prevalence rate estimates were adjusted for age, sex, and race/ethnicity with direct standardization to the 2010 KPSC young adult distribution.13 The prevalences of health conditions then were compared between new members (enrolled < 1 year) and long-term members (enrolled at least 3 years). We also conducted a secondary analysis focused on obesity (see Sidebar: Body Weight and Height).14-17

All analyses were performed using SAS statistical software version 9.3 (SAS Institute Inc, Cary, NC).


Young adult enrollment increased by 65% (145,000)—from 223,000 pre-ACA to 368,000 post-ACA (Figure 1).

Demographics after ACA passage (2010-2015) compared with during the pre-ACA period (2008-2010) essentially were unaltered with regard to age, race/ethnicity, neighborhood education, and KPSC membership duration (Table 1). No changes in ambulatory, inpatient, Emergency Department, or virtual service use were observed. There was a trend toward halting the increase in high-deductible insurance plans (standardized difference of 0.22 pre-ACA vs 0.05 post ACA) and an increase in individuals with state-subsidized health plans such as Medi-Cal (standardized difference of 0.06 pre-ACA vs 0.25 post-ACA). In addition, the proportion of young adults from high-income neighborhoods post-ACA decreased and shifted slightly toward young adults from lower income neighborhoods (standardized difference of 0.14 pre-ACA vs -0.30 post-ACA).

The age-, sex-, and race-adjusted prevalences of health conditions were low. Most health conditions had a prevalence lower than 1% with the exceptions of drug abuse, depression, and chronic pulmonary disease. The prevalence of all health conditions remained stable when comparing pre- and post-ACA periods (Table 2), although hypothyroidism increased marginally post-ACA (standardized difference 0.15).

We also examined whether the prevalence of health conditions changed among young adults who became new members vs young adults who were long-term members pre-ACA, during ACA implementation, or post-ACA. The age-, sex-, and race-adjusted prevalences for all health conditions were comparable between young adults who were members for less than 1 year and those with long-term memberships lasting 3 or more years (Table 3, all standardized differences ≤ 0.20).

We then examined changes in the prevalence of overweight and obesity as a marker for future health risks. The prevalence of overweight and obesity in young adults was relatively stable for most demographic groups between pre- and post-ACA implementation, as indicated by modest standardized differences (Table 4).

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To our knowledge, this is the first study to investigate the health of young adults enrolled in a Health Plan before and after ACA passage. Results suggest that the number of KPSC young adult members has increased since the ACA took effect. Young adults who obtained new health care coverage at KPSC did not have more chronic health conditions (including obesity) than those who had coverage in the Health Plan for more than 3 years.

As previously shown, the ACA led to a substantial increase in the proportion of young adults with health insurance.2,18,19 Health care access is a concern, especially for individuals with low income and educational backgrounds.1 The ACA provision of insurance was intended to improve health care utilization and decrease out-of-pocket expenses for those who previously were uninsured or underinsured. Uninsured young adults are likely to delay or forego care and are high utilizers of acute care.20,21 But young adults are a group of high importance for society. Health insurance helps young adults maintain and improve their health and productivity.18,20,22 Young adulthood also provides an important opportunity for chronic disease prevention.18 Including young adults in the insurance pool also helps society offset the higher costs associated with care for older adults. Future research will demonstrate if young adults retain health insurance coverage over time and if insurance coverage during young adulthood influences health status, quality of life, and longevity through the years. Because high-deductible plans are associated with reduced use of preventive services,23,24 more evidence is needed to determine the effects of coverage type on health for young adults.

These findings do not indicate that new young adult members are less healthy than long-term members. These data included the prevalence of overweight or obesity, which is an indicator of future health risks. Modest changes in the prevalence of health conditions occurring during the pre-ACA period coincide with national trends that reveal increasing asthma (included in chronic pulmonary disease) and depression incidence and decreasing rates of drug abuse.25,26 

These results must be interpreted with caution because they express only secular trends without a true control group and do not distinguish between changes in diagnosing and coding of certain health conditions attributable to evolving billing procedures or other reasons. Results are based solely on diagnosis codes, which may lead to underestimation of conditions that are undercoded such as depression27 even if the validity of diagnosis codes is relatively high in this integrated health care system.28-31 Another limitation stems from uncertainty regarding new members’ health care access before enrollment in a KPSC Health Plan. We are unable to distinguish members who previously had no access to health care from those who had access elsewhere before enrolling in a KPSC Health Plan. We also do not have information that allows us to compare young adults who joined the KPSC Health Plan with those who joined other Health Plans. Hence, we can only draw conclusions regarding young adults who gained access to KPSC health care, not to health care in general. Further, these results may not be generalizable to the entire US population because this study sample encompasses only young adults from Southern California.


The ACA resulted in an increase of young adults enrolled in the KPSC Health Plan. No differences were observed in the prevalence of many health conditions between young adults who were newly enrolled and existing long-term young adult members. These data may alleviate concerns that young adults who newly enroll in health insurance may have more chronic health conditions than those who do not. Additional research is needed to assess whether these young adults will maintain their coverage after turning age 26, at which time they will be removed from their parents’ insurance policies.

Disclosure Statement

The author(s) have no conflicts of interest to disclose.


Brenda Moss Feinberg, ELS, performed a primary copy edit. 

How to Cite this Article

Gervacio GB, Sidell M, Li X, et al. Health status of young adults with insurance coverage before and after Affordable Care Act passage. Perm J 2019;23:17-223. DOI:

Author Affiliations

1 Department of Research and Evaluation, Kaiser Permanente, Pasadena, CA

2 Precision for Medicine Oncology and Rare Disease, Carlsbad, CA

3 Merck KGaA, Darmstadt, Germany

Corresponding Author

Corinna Koebnick, PhD (

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Keywords: Affordable Care Act, health care, obesity, socioeconomic status, young adult


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