HDHP enrollment is associated with lower odds of smoking only among individuals who chose to enroll in an HDHP. Lower rates of unhealthy behaviors among HDHP enrollees may be a reflection of individuals who choose these plans.

HDHP enrollment was associated with lower odds of smoking among individuals with ESI and a choice of plans (AOR 0.55, 95% CI 0.33–0.90) and those with non-group coverage (AOR 0.64, 95% CI 0.34–1.22), though the latter association was not statistically significant. HDHP enrollment was not associated with lower odds of smoking among individuals with ESI and no choice of plans (AOR 1.04, 95% CI 0.69–1.56).

We classified subjects as HDHP or traditional health plan enrollees with employer-sponsored insurance (ESI) and no choice of plans, ESI with a choice of plans, or coverage through the non-group market. We used multivariate logistic regression to measure associations between HDHP enrollment and daily smoking within each of the 3 coverage source groups while controlling for potential confounders.

Funding: The US Department of Veterans Affairs and the Robert Wood Johnson Foundation funded the study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. These contents do not represent the views of the Department of Veterans Affairs, the United States Government, or the Robert Wood Johnson Foundation.

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

An alternative explanation for these lower rates of unhealthy behaviors among HDHP enrollees is that individuals who engage in healthy behaviors at high rates choose HDHPs over traditional health insurance plans [13] , [14] , [15] because they expect to have few health expenditures and therefore are willing to accept high deductibles in exchange for the low monthly premiums characteristic of HDHPs [16] . If the lower odds of unhealthy behaviors among HDHP enrollees are driven largely by this individual plan self-selection instead of ex ante moral hazard, these lower odds would exist only among individuals who could choose their health plan and not among those who did not have a choice of health plans. However, it is currently unknown whether lower odds of any unhealthy behaviors are found just among HDHP enrollees who chose their plan. The objective of this study was to test whether choice of health plan, rather than ex ante moral hazard, can explain the healthier behaviors among HDHP enrollees by determining whether lower odds of one exemplar unhealthy behavior – daily smoking – are found only among HDHP enrollees who could choose their plan.

The theoretical basis for believing HDHPs might change health behavior is based on the idea that because health insurance protects beneficiaries from facing the full financial consequences of medical care, beneficiaries might engage in more unhealthy behaviors than they would without this financial protection. This behavioral response to insurance, ex ante moral hazard, has little empirical support in the health services research literature [5] , [6] , [7] , [8] . Nevertheless, the strong cross-sectional relationship between HDHP enrollment and lower rates of unhealthy behaviors [9] , [10] , [11] , [12] has often been cited to support the belief that HDHPs leverage ex ante moral hazard to promote healthy behaviors.

One policy approach promoted as a way to reduce rates of unhealthy behaviors in the United States is greater enrollment in high-deductible health plans (HDHPs) [1] , [2] , which are private health insurance plans that feature deductibles of at least $1,100 per individual and $2,200 per family before most services are covered. Advocates for expansion of enrollment in HDHPs assert that placing patients at risk for the initial cost of their care through these plans encourages them to take greater responsibility for their health [3] , [4] .

Materials and Methods

Ethics Statement The study procedures were reviewed by the University of Pennsylvania Institutional Review Board (IRB) and deemed exempt from IRB review.

Conceptual Framework Adults with private health insurance coverage in the United States have different degrees of health plan choice depending on whether they obtained their coverage from an employer who did not offer a choice of plans, an employer who offered a choice of plans, or the non-group market (Figure 1). PPT PowerPoint slide

PowerPoint slide PNG larger image

larger image TIFF original image Download: Figure 1. Conceptual framework. HDHP = high-deductible health plan. https://doi.org/10.1371/journal.pone.0056154.g001 In the first group, employer-sponsored insurance (ESI) without plan choice, an individual is only offered one health insurance plan through the employer of an adult in their household. The employer chooses the plan to offer and the employee is left with a choice of opting in or not. Since there is no option to select among plans, this group contains the least potential to choose a health plan. In the second group, employer-sponsored insurance (ESI) with plan choice, an individual has a choice between one or more health plans either because the employer of an adult in their household offers more than one plan to its employees or more than one adult in the household is eligible for health insurance through their employer. In this group, there is greater ability to choose a plan than in the ESI without plan choice group because an individual can select a plan from amongst several offerings [17], though the choice set is constrained by the range of plans offered to that household. In the third group, non-group coverage, an individual purchases health insurance directly from an insurer. In this setting, there is the greatest potential to choose a plan, as an individual can select from amongst the many options the non-group market offers. The choice set is constrained only by medical underwriting [18] and an individual's willingness and ability to pay the quoted premiums. Within each of these 3 coverage source groups, an individual is enrolled in either an HDHP or a traditional health insurance plan. The different degrees of health plan choice in each group offer a unique opportunity to explore the potential mechanisms underlying previously observed associations between HDHP enrollment and unhealthy behaviors such as smoking, as the choice to engage in an unhealthy behavior should not be influenced by an individual's degree of health plan choice. If, for example, the association between HDHP enrollment and an unhealthy behavior like smoking is driven primarily by ex ante moral hazard, then this association should be found in each coverage source group (i.e., irrespective of the degree of health plan choice). On the other hand, if the association between HDHP enrollment and an unhealthy behavior like smoking is driven more by selection of healthier individuals into HDHPs in settings of plan choice, then this association should be found only among individuals with the greatest ability to choose an HDHP (i.e., the ESI with plan choice and non-group coverage groups) and not among individuals with the least ability to choose an HDHP (i.e., the ESI without plan choice group).

Data Source The sample was comprised of 6,941 privately insured non-elderly adults in the 2007 Health Tracking Household Survey (HTHS). The 2007 HTHS was conducted between April 2007 and January 2008 by the Center for Studying Health System Change and Mathematica Policy Research, Inc., and used random digit dialing to collect data by telephone from 17,797 people in 9,407 households in the contiguous United States. The household response rate was 47.2 percent [19]. The survey collected demographic information and data on health insurance, employment, and health characteristics for each adult in every sampled household. If any individuals in the household had private health insurance, information was collected on who was covered by the plan, how that plan was obtained (i.e., through an employer or through purchase in the non-group market), and whether the plan had a deductible. If the plan had a deductible, information was collected on the size of the deductible. Individuals with employer-sponsored insurance (ESI) were asked whether that employer offered 1 health insurance plan to its employees or more than 1 plan; no data were collected on the types of plans the employer offered to that individual. Those who were employed but not a policyholder of an employer-sponsored plan were asked whether they were eligible for health insurance through their employer. Each adult respondent was also asked about his or her smoking; those who indicated they had smoked at least 100 cigarettes in their entire life were asked whether they currently smoke cigarettes every day, some days, or not at all.

Main Predictor Variables For analysis, we divided individuals into 1 of 3 coverage source groups discussed in the Conceptual Framework section. The first group was ESI without plan choice. We assigned individuals to this group if they were enrolled in an ESI plan through an employer that did not offer a choice of health plans and no one else in that family insurance unit [19] was eligible for employer-sponsored coverage. The second coverage source group was ESI with plan choice. We assigned individuals to this group if they had ESI and either the employer from which the coverage was obtained offered a choice of plans or another adult in the family insurance unit was also eligible for coverage through their employer. The third coverage source group was individuals with non-group coverage. We assigned individuals to this group if they had private health insurance coverage that was not obtained through an employer. In each of these 3 coverage source groups, we classified individuals as being enrolled in an HDHP as defined by US federal law: a private health insurance plan with an annual individual deductible of at least $1,100 or a family deductible for at least $2,200 [20]. All other privately-insured individuals in the sample were classified as traditional plan enrollees.

Primary Outcome Variable The primary outcome variable was specified a priori. Individuals who stated they currently smoke cigarettes every day were classified as daily smokers.

Covariates Data on gender, age, annual household income, race/ethnicity, education, chronic conditions, time in the current health insurance plan, risk-taking, employment status, marital status, parental status, and US Census region were obtained from the survey. County metropolitan statistical area category was obtained from the 2007 Area Resource File. All covariates were operationalized as categorical variables with mutually-exclusive categories. Age was defined as 3 categories: 18 to 25 years, 26 to 45 years, or 46 to 64 years. Annual household income was operationalized as 3 categories: less than $50,000; $50,000 to $100,000; or greater than $100,000. Race and ethnicity data were collected in categories used in the US Census. Education was operationalized as a dichotomous variable based on whether an individual had at least 16 years of education (i.e., a college degree). Having a chronic condition was operationalized as a dichotomous variable based on whether an individual reported a history of heart disease, cancer, diabetes, chronic obstructive pulmonary disease, hypertension, arthritis, asthma, or depression. Length of time in one's current health insurance plan was defined as more than 12 months or less than 12 months. Respondents who agreed with the statement, “I'm more likely to take risks than the average person” were classified as risk-takers. Employment status was operationalized as 3 categories: full-time, part-time, or not working.