Results Summary

What was the research about?

Asthma is a health problem that makes it hard for people to breathe. People often rely on insurance plans to help pay for care and medicine to control asthma. But some types of plans provide more help than others. With high-deductible health plans, or HDHPs, people pay more toward the cost of their care than they do with low-deductible plans. Higher costs may affect whether people can afford medicines. For this reason, some HDHPs have a list of medicines that are free to people, like asthma medicines.

The research team wanted to learn about the impact of insurance changes on health care for people with asthma. They did two studies. The first compared people whose employer switched to an HDHP versus people who stayed on a low-deductible plan. The second compared people whose HDHP added a free medicine list versus people whose plan didn’t.

What were the results?

Compared with people who stayed on low-deductible plans, people whose employers switched to HDHPs:

  • Filled fewer prescriptions for long-acting inhaled asthma control medicines and took these medicines less often
  • Had higher out-of-pocket costs for asthma care

Among people on HDHPs, people whose plan added a free medicine list had lower out-of-pocket costs than people whose plan didn’t add such a list. Use of asthma control medicines didn’t differ between the two groups.

The two studies found no differences in:

  • Use of other types of asthma control medicines, like pills or short-acting inhaled asthma control medicines
  • Asthma attacks
  • How often people filled prescriptions for albuterol, a medicine used during an asthma attack, or spacers, which hold asthma inhalers in place, making it easier to breathe the medicine in

What did the research team do?

The research team reviewed insurance claims for people with asthma. All had insurance through their jobs.

Study 1 included insurance claims from 2002 to 2014 for 184,579 children and adults ages 4–64 who had asthma. Of these, 72 percent were White, 7 percent were Hispanic, 2 percent were Asian, 2 percent were Black, and 18 percent were more than one race or ethnicity. Also, 54 percent were women.

Study 2 included claims from 2004 to 2017 for 12,174 children and adults ages 4–64 who had asthma. Of these, 78 percent were White, 7 percent were Black, and 7 percent were Hispanic; 56 percent were women.

People with asthma, parents of children with asthma, a drug company, insurers, employers, and patient groups gave input on the study.

What were the limits of the study?

The study didn’t account for some differences between people whose plans did and didn’t change, like how severe their asthma was. These differences may have affected the results.

Future research could look at how HDHPs affect people with severe asthma and at other health outcomes like family stress and well-being.

How can people use the results?

People with asthma and employers can use the results when considering types of insurance.

Final Research Report

View this project's final research report.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also assesses how the project addressed PCORI’s Methodology Standards. During peer review, experts read a draft report of the research and provide comments about the report. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. These reviewers cannot have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve descriptions of the conduct of the study or to clarify the connection between results and conclusions. Sometimes, awardees revise their draft reports twice or more to address all of the reviewers’ comments. 

Peer reviewers commented and the researchers made changes or provided responses. Those comments and responses included the following:

  • The reviewers questioned the researchers’ approach to missing data, particularly as related to imputation of missing deductible levels. The researchers added information to their appendix about their imputation model, methods for estimating accuracy, and their percent of enrollees with imputed deductible data.
  • The reviewers noted that the report was unclear on what variables were included in the data matching models for aim 3 of the report. The researchers added information to the report’s section on matching, indicating that the covariates for the models were noted in the footnote of one of the results tables.
  • The reviewers asked the researchers to provide justification for excluding data from the last month of the baseline year and the first month of the follow-up year. The researchers explained that they had found that for enrollees in the high-deductible health plans (HDHPs), participants would stockpile medications at the end of the year, which also led to a decline in medication use at the beginning of the next year. These changes could affect the analyses, so the two months were left out.
  • The reviewers noted the low proportion of Black or Hispanic/Latino/a study participants and wondered whether this could be related to the types of people who enroll in HDHPs. The researchers acknowledged that their study sample had lower proportions of these patients with asthma than the general population, which they agreed could be a reflection of population characteristics for commercially insured individuals.
  • The reviewers asked the researchers to elaborate on the implications of the small sample size and low participation in their COVID-19 enhancement project. The researchers expanded their discussion regarding the limited conclusions that are possible for this enhancement project but indicated that there was much to learn from this project regarding the feasibility and acceptability of navigation interventions. They also discussed alternative strategies for future research.

Conflict of Interest Disclosures

Project Information

Alison A. Galbraith, MD, MPH
Harvard Pilgrim Health Care ,Inc.
Comparing Patient-Centered Outcomes for Adults and Children with Asthma in High-Deductible Health Plans with and without Preventive Drug Lists

Key Dates

December 2016
January 2023

Study Registration Information


Has Results
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Last updated: April 12, 2024