Introduction

A Usual Source of Care (USC) refers to a physician or medical facility that individuals typically visit when they are ill or in need of medical consultation [1]. It is most commonly measured through survey questions and is frequently used as a variable in health services research [2-6]. While simply having a regular healthcare facility does not guarantee adequate access to primary care, it is considered a critical prerequisite for receiving effective and comprehensive primary care services. Patients who lack an ongoing relationship with a healthcare provider are less likely to receive comprehensive care [7]. In contrast, having a usual place of care is strongly associated with a higher likelihood of receiving both preventive and treatment services typically offered in primary care settings. Moreover, this association often exceeds the explanatory power of traditional sociodemographic and access-related predictors—such as insurance status—when it comes to healthcare utilization [7]. Numerous previous studies have also confirmed that ensuring individuals have a USC is essential for improving access to preventive services and for promoting better health outcomes [8-11].

In both the United States and South Korea, where healthcare systems rely heavily on privately delivered services, having a USC has been shown to be strongly associated with increased utilization of preventive services [12,13]. Even after adjusting for various demographic and socioeconomic factors—including self-rated health status, patient activation, and insurance coverage—prior research has found that individuals with a USC are significantly more likely to receive all seven recommended preventive services [7]. Furthermore, the presence of a USC has been shown to be a stronger predictor of receiving key screenings—such as blood pressure, cholesterol, and blood glucose tests—than other commonly emphasized variables, including gender, perceived health, insurance status, urban residence, and secondary education. These findings highlight the pivotal role that a continuous and accessible usual source of care plays in improving preventive care delivery, particularly in systems dominated by private sector service provision [7].

While having a USC has been shown to be effective in increasing the use of health screenings and preventive services, it does not necessarily guarantee improvements in health behaviors [14]. A review of previous studies on USC and health behaviors suggests that, among individuals with chronic conditions such as hypertension, diabetes, and hyperlipidemia, having a USC does not appear to influence smoking or alcohol consumption, but may be associated with increased physical activity [4]. Similarly, among middle-aged and older adults, USC ownership was generally not associated with healthier smoking or drinking behaviors but was positively related to improvements in physical activity [14]. In addition, patients who gave higher ratings to the quality of primary care services were more likely to report healthy drinking habits, compared to those with lower evaluations [15,16]. Moreover, while USC did not significantly affect smoking behavior, it was found to be associated with greater use of preventive services such as cancer screenings [5]. In summary, existing studies on the relationship between USC and health behavior show that the relationship between USC and health behaviors remains mixed and inconclusive across existing studies, especially when it comes to behaviors like smoking and alcohol use.

In Korea, the role of primary care is not clearly defined within the healthcare delivery system, so patients can access medical services at private clinics, secondary hospitals, or large tertiary hospitals with few restrictions [17]. As a result, while the rate of patients having a usual source of care is 79% in the U.S., 84% in Canada, and 89% in the U.K., it is relatively low in Korea at 53.4% as of 2021 [2,18,19]. Unlike countries with a strong primary care orientation, Korea lacks consistency in patients' first point of contact. Moreover, as healthcare providers tend to open clinics according to their specialties, comprehensiveness and care coordination are often lacking [2]. Given this context, even when patients do have a regular healthcare provider, it's important to also assess whether that provider performs key primary care functions—such as comprehensiveness and coordination—to accurately interpret the impact of having a usual source of care on health behaviors. However, very few studies have included such variables in their analysis so far.

In January 2015, the South Korean government raised tobacco prices and allocated the resulting revenue to support smoking cessation treatments, including covering the cost of medications, counseling, and public awareness campaigns [20]. As a result, starting February 25, 2015, smokers could officially receive cessation treatment at medical institutions through the national smoking cessation support program. The 6-month cessation success rate was around 40%, comparable to that of local public health center programs. In addition, to build a chronic disease management system centered on local clinics, the Korean government launched a pilot payment model for managing hypertension and diabetes in September 2016. A primary care-based chronic disease management pilot project was implemented from January 2019 to September 2024. Currently, the program has been expanded to include all primary care institutions, and it also incorporates lifestyle modification education as part of its services [21].

As such, recent changes in various national health policies in Korea suggest that having a USC helps improve health behaviors such as smoking cessation, reduced alcohol consumption, and increased physical activity. Furthermore, the role of primary care within the healthcare delivery system is expected to be emphasized. This study utilizes post-2015 data, after the implementation of such government policies targeting both patients and healthcare providers, to analyze the relationship between the type of USC and the practice of healthy behaviors. The hypothesis of this study is that individuals with a usual source of care that provides both comprehensive and coordinated services are more likely to engage in healthy behaviors such as smoking cessation, reduced alcohol consumption, and increased physical activity.

This study aims to investigate the relationship between types of USC and health behaviors among adults aged 19 years and older, using annual panel data from the Korea Health Panel collected between 2019 and 2021.

Methods

Study design

This study is a cross-sectional investigation examining the between Usual Source of Care (USC) type and health behaviors among adults aged 19 years and older using the 2019-2021 Korea Health Panel Annual Data (Version 2.2).

Participants & setting

This study utilized data from the Korea Health Panel Survey (KHPS), jointly conducted by the Korea Institute for Health and Social Affairs (KIHASA) and the National Health Insurance Service (NHIS). Specifically, the analysis was based on annual data from 2019 to 2021 (Version 2.2). The final study sample included 11,498 adults aged 19 years or older.

Measurements

Smoking Status was assessed by asking, “Do you currently smoke conventional cigarettes?” Respondents who answered “I smoke every day” or “I smoke occasionally” were classified as the smoking group. Those who responded “I used to smoke but no longer do” or “I have never smoked” were categorized as the smoking cessation group.

Alcohol Abstinence was defined as drinking less than once per month over the past year. Alcohol use was measured using the question, “How often have you consumed alcohol in the past year?” Participants who answered “I have never had a drink in my life,” “I have not had a drink in the past year,” or “Less than once a month” were classified as non-drinkers. Those who reported drinking “About once a month,” “2–4 times a month,” “2–3 times a week,” “4 or more times a week,” or “Almost every day” were categorized as drinkers.

Physical Activity was measured by the question, “In the past year, have you regularly participated in sports or exercise, including walking?” Based on responses, participants were classified into the exercise group or non-exercise group.

The independent variables included in this study were: gender, age, educational attainment, marital status, private health insurance coverage, annual number of outpatient medical visits, type of USC, and average monthly household income. Total household income was calculated by summing the earned and business income of all household members, along with total household assets, regular income, and non-regular income.

The type of USC in this study encompassed the primary care attributes of first contact, comprehensiveness, and coordination, excluding continuity. The survey used in the study consisted of four items: First, Usual Source of Care Institution: Respondents were asked, “When you are sick or need an examination or treatment consultation, do you have a medical institution (a regular clinic or hospital) that you usually visit?” with response options of “Yes” or “No.” Second, Usual Source of Care Physician: Respondents were asked, “When you are sick or need an examination or treatment consultation, do you have a physician (a regular doctor) that you usually visit?” with response options of “Yes” or “No.” Third, Comprehensiveness of Usual Physician’s Service: This was assessed with the question, “Does the doctor resolve most of your common health problems?” with response options of “Almost always,” “Mostly,” “Sometimes,” “Rarely,” and “Almost never.” Fourth, Coordination Function of Usual Physician: This was measured with the question, “Does the doctor appropriately refer you to necessary health-related facilities or personnel for health management? (e.g., specific specialists or hospitals, social welfare centers, long-term care facilities, caregivers, smoking cessation counseling services, etc.)” with the same five-point scale as above: “Almost always,” “Mostly,” “Sometimes,” “Rarely,” and “Almost never.”

In this study, the types of USC were classified into five categories using four survey items: Type 1: No USC clinic and no usual physician; Type 2: Has a usual USC clinic, but no usual physician; Type 3: Has a usual physician, but lacks both comprehensiveness and coordination functions; Type 4: Has a usual physician, with either comprehensiveness or coordination function; Type 5: Has a usual physician, with both comprehensiveness and coordination functions.

Data collection/Procedure

This study utilized data from the 2019~2021 Korea Health Panel Survey (KHPS), jointly conducted by the Korea Institute for Health and Social Affairs (KIHASA) and the National Health Insurance Service (NHIS), and was used after submitting a data use agreement to the Korea Institute for Health and Social Affairs (KIHASA).

Data analysis

A multivariate logistic regression analysis was employed to examine the relationship between the type of USC and health behaviors. The dependent variables in this analysis were three major health behaviors: smoking cessation, alcohol abstinence, and engagement in regular physical activity.

Ethical consideration

The Korea Health Panel Survey was approved by Statistics Korea pursuant to Article 18 of the Statistics Act (Approval No. 920012). For this study, an exemption from review was granted by the Institutional Review Board (IRB No.: U1IRB2025-02) of the university to which the researcher belongs.

Results

General characteristics of the study population

The general characteristics of the study population are as follows women outnumber men at 54.5% to 45.5%, with the largest age group being 65 and older at 41.6%, followed by 31.5% in the 19-49 age group and 26.9% in the 50-64 age group. 68.4% have a spouse, 31.6% do not, and 33.9% have a college degree or higher, followed by 29.9% with a high school degree, 22.8% with an elementary school degree or less, and 13.4% with a middle school degree. The average monthly household income is KRW 3.94 million, and the average number of outpatient medical visits per year is 18.7. 73.3% had private health insurance, compared to 26.7% who did not, and 54.4% had chronic diseases, compared to 45.6% who did not.

Among the types of usual sources of care, the most common was Type 1 (48.9%), which includes facilities with no designated hospital or physician. The remaining 51.1% of respondents reported having a usual source of care: Type 2 (17.4%) had a usual hospital but no physician; Type 4 (15.2%) had a usual physician with either comprehensiveness or coordination of care; Type 5 (12.4%) had a usual physician with both comprehensiveness and coordination of care; and Type 3 (6.2%) had a usual physician but lacked both comprehensiveness and coordination (Table 1).

According to Table 2, the distribution of usual source of care types varied significantly depending on key explanatory variables such as age, education level, and whether the individual had been diagnosed with a chronic disease. For example, among individuals aged 19 to 49, 65.6% fell into Type 1—those without a usual source of care—which is nearly twice as high as the 34.8% in the 65 and older age group.

Similarly, among those with a college degree or higher-who are likely to include a greater proportion of younger adults 59.3% had no usual source of care (Type 1). This is 23 percentage points higher than the 36.4% among those with only an elementary school education or less, a group likely to include more older adults.

In the distribution by chronic disease status, 69.6% of individuals without a chronic disease diagnosis-who tend to be younger-were classified as Type 1, compared to just 31.9% among those diagnosed with chronic conditions, who are generally older. This represents more than a twofold difference.

In the distribution of usual source of care types by smoking and drinking status, Type 1 (no usual source of care) was less prevalent among non-smokers and non-drinkers—groups that are expected to include a larger proportion of older adults. In contrast, the rate of not having a usual source of care was higher among smokers and monthly drinkers, who are more likely to be younger (Table 2). These findings align with previous research from the Korea Disease Control and Prevention Agency (Korea Disease Control and Prevention Agency, 2022), which reported that smoking cessation and alcohol abstinence rates tend to increase with age [22].

As shown in Table 1, the current smoking rate indicates that 84.1% of respondents were in the non-smoking group, compared to 15.9% in the smoking group. For monthly alcohol consumption, 52.2% were in the non-drinking group, slightly more than the 47.8% in the drinking group. Regarding regular physical activity, 50.1% were in the exercise group, compared to 49.9% in the non-exercise group.

Differences in health behaviors (smoking cessation, alcohol abstinence, physical activity) by general characteristics

Regarding smoking cessation, the rate was significantly higher among women (97.0%) than men (68.0%) (p<.001). By age group, those aged 65 and older had the highest smoking cessation rate at 90.8%, followed by those aged 50–64 (80.2%) and 19–49 (77.9%) (p<.001). Individuals with a spouse had a higher cessation rate (85.1%) compared to those without a spouse (81.6%) (p<.001). By educational level, those with an elementary school education or less had the highest cessation rate (92.4%), followed by middle school graduates (86.0%), university graduates or higher (81.8%), and high school graduates (79.3%) (p<.001). The average monthly household income of smokers was 4.089 million KRW, which was higher than that of non-smokers at 3.833 million KRW (p=.001). As for private health insurance, those without insurance reported a higher cessation rate (87.5%) compared to those with insurance (83.0%) (p<.001). Individuals diagnosed with chronic diseases had a cessation rate of 87.8%, higher than the 79.5% among those without such diagnoses (p<.001). In addition, non-smokers had more annual outpatient visits—an average of 19.87 visits—compared to 14.09 visits among smokers (p<.001).

In terms of USC types, the highest smoking cessation rate was observed in Type 4—those with a usual physician but with only either comprehensiveness or coordination—at 89.0%. This was followed by Type 3 (a usual physician without either function) at 87.7%, Type 2 (a usual hospital but no physician) at 86.7%, Type 5 (a usual physician with both comprehensiveness and coordination) at 86.3%, and finally Type 1 (no usual hospital or physician) at 80.5% (p<.001).

In terms of alcohol abstinence, women had a significantly higher non-drinking rate (66.2%) compared to men (35.4%) (p<.001). By age group, individuals aged 65 and older showed the highest non-drinking rate at 69.1%, followed by those aged 50–64 (45.6%) and 19–49 (33.9%) (p<.001). Those without a spouse had a higher non-drinking rate (56.9%) compared to those with a spouse (50.2%) (p<.001). By educational attainment, individuals with an elementary school education or less reported the highest non-drinking rate at 75.6%, followed by middle school graduates (60.8%), high school graduates (46.3%), and those with a college degree or higher (37.8%) (p<.001). Individuals without private health insurance had a higher non-drinking rate (67.8%) compared to those with insurance (46.7%) (p<.001). Furthermore, the non-drinking rate was higher among individuals diagnosed with a chronic disease (62.8%) compared to those without a diagnosis (39.3%) (p<.001).

Looking at USC types, the highest non-drinking rate was found in Type 4 (with a usual physician and either comprehensiveness or coordination) at 62.4%. This was followed by Type 2 (hospital only, no physician) at 58.2%, Type 3 (physician only, without comprehensiveness or coordination) at 54.6%, Type 5 (physician with both comprehensiveness and coordination) at 53.8%, and Type 1 (no hospital or physician) at 46.2% (p<.001).

Regarding physical activity, men had a slightly higher rate of regular exercise (51.4%) compared to women (49.1%) (p=.021). By age group, individuals aged 65 and older had the highest rate at 54.3%, followed by those aged 50–64 (51.0%) and 19–49 (43.2%) (p<.001). Those with a spouse reported higher physical activity (51.2%) than those without (47.6%) (p<.001). Education level also showed a positive correlation: college graduates or higher had the highest rate of regular exercise (53.0%), followed by middle school graduates (52.5%), high school graduates (50.2%), and those with an elementary school education or less (44.4%) (p<.001). Individuals with private health insurance exercised more regularly (50.9%) than those without insurance (48.5%) (p=.035). People diagnosed with chronic diseases also had a higher rate of regular physical activity (52.0%) than those without a diagnosis (47.9%) (p<.001).

When examined by USC type, Type 4—those with a usual physician offering either comprehensiveness or coordination—showed the highest physical activity rate at 54.8%. This was followed by Type 2 (hospital only, no physician) at 53.7%, Type 3 (physician only, no comprehensiveness or coordination) at 51.6%, Type 5 (physician with both functions) at 50.0%, and Type 1 (no regular provider) at 47.2% (p<.001) (Table 3).

Factors associated with health behaviors: Smoking cessation, alcohol abstinence, and physical activity

1. Factors associated with smoking cessation

Women were 17.42 times more likely to be non-smokers compared to men (p<.001). Compared to those aged 19–49, individuals aged 65 and older were 3.93 times more likely to quit smoking (p<.001), while those aged 50–64 were 1.37 times more likely (p=.001). Respondents without a spouse were 43% less likely to quit smoking (OR=0.57, p<.001) than those with a spouse. Regarding education, individuals with a college degree or higher were 1.58 times more likely to have quit smoking compared to those with an elementary school education or less (p=.001). As total household income increased, the likelihood of smoking cessation increased slightly (OR=1.00, p<.001). Those without private health insurance were 1.32 times more likely to quit smoking than those with insurance (p=.002). A higher number of annual outpatient visits was also associated with a slightly higher likelihood of smoking cessation (OR=1.01, p<.001). Regarding the type of USC, individuals in Type 4—those with a regular physician providing either comprehensiveness or coordination—were 1.24 times more likely to quit smoking compared to those in Type 1, who had neither a regular facility nor a physician (p=.047). Similarly, those in Type 5, who had a usual physician providing both comprehensiveness and coordination, were 1.25 times more likely to quit smoking than Type 1 individuals (p=.038).

2. Factors associated with alcohol abstinence

Women were 4.25 times more likely to abstain from alcohol compared to men (p<.001). Compared to individuals aged 19–49, those aged 50–64 were 1.55 times more likely, and those aged 65 and older were 2.89 times more likely to be non-drinkers (p<.001 for both). Regarding education level, compared to individuals with elementary school education or less, those with middle school education were 18% less likely to abstain (OR=0.82, p=.015), high school graduates were 25% less likely (OR=0.75, p<.001), and college graduates or higher were 17% less likely (OR=0.83, p=.033). As household income increased, the likelihood of alcohol abstinence decreased slightly (OR=1.00, p<.001). Respondents without private health insurance were 1.54 times more likely to abstain compared to those with insurance (p<.001). A higher number of annual outpatient visits was associated with a slightly increased likelihood of alcohol abstinence (OR=1.01, p<.001). However, individuals diagnosed with chronic diseases were 19% more likely to abstain compared to those without such diagnoses (OR=1.19, p=.007). Regarding the USC, compared to Type 1 (no regular facility or physician), individuals in Type 2 (hospital only, no physician) and Type 4 (physician with either comprehensiveness or coordination) were each 1.16 times more likely to abstain from alcohol (p=.027 and p=.042, respectively).

3. Factors associated with engagement in physical activity

Compared to individuals aged 19–49, those aged 50–64 were 1.88 times more likely to engage in regular physical activity (p<.001), and those aged 65 and older were 3.21 times more likely (p<.001). Regarding education, compared to individuals with an elementary school education or less, those who completed middle school were 1.48 times more likely to engage in regular exercise (p<.001), high school graduates were 1.92 times more likely (p<.001), and college graduates or higher were 3.02 times more likely (p<.001). Individuals without private health insurance were 19% less likely to engage in physical activity compared to those with insurance (OR=0.81, p<.001). Additionally, more frequent annual outpatient visits were associated with a slight decrease in the likelihood of exercising (OR=1.00, p=.010). Regarding USC types, individuals in Type 2 (hospital only, no physician) were 1.24 times more likely to engage in physical activity than those in Type 1 (no regular hospital or physician) (p<.001). Similarly, those in Type 4 (physician with either comprehensiveness or coordination) were 1.23 times more likely to exercise (p=.001) (Table 4).

Discussion

This study aimed to examine the relationship between types of USC and health behaviors—including smoking cessation, alcohol abstinence, and engagement in physical activity—among Korean adults aged 19 and older who participated in the 2021 Korea Health Panel Survey.

According to the findings, the USC ownership rate in 2021 was 51.1%, which represents a substantial increase of over 15 percentage points compared to 35.4% in 2012, as reported by a previous study using the same Korea Health Panel dataset. Several factors may have contributed to this notable rise over the past nine years. The increase is likely influenced by rapid population aging and a higher prevalence of chronic diseases, which may have led to a greater need for regular medical providers. Additionally, government incentives promoting the establishment of a usual source of care have likely played a key role. In particular, the Korean government launched the Primary Care Chronic Disease Management Pilot Program in 2019, with plans to fully implement it by 2025. Under this program, patients diagnosed with hypertension or diabetes can register with a clinic or hospital to receive medication management and lifestyle counseling [23,24]. In return, they benefit from reduced out-of-pocket costs and are eligible for financial support to encourage healthy behaviors. These policy measures appear to have significantly contributed to the increased rate of USC ownership among Korean adults.

While this study found that 51.1% of Korean adults had a usual source of care (USC) in 2021, a multinational study conducted between 2022 and 2023 across 14 countries reported a slightly higher USC rate of 54.6% for Koreans. However, this remains significantly lower than the average USC rate of 74.6% among respondents from all 14 countries [7]. Moreover, only 27.6% of Koreans were found to have a USC physician who provided at least one of the two core attributes of primary care—comprehensiveness or coordination. This raises an important question: Does having a usual source of care that embodies core principles of primary care, such as comprehensiveness and coordination, correlate with healthier lifestyle behaviors?

The results of this study suggest that having a usual source of care (USC) is associated with healthier lifestyle behaviors. In particular, individuals who had a USC that possessed at least one core primary care attribute—either comprehensiveness or coordination—were 1.24 to 1.25 times more likely to have quit smoking compared to those without a USC. These findings differ from those of previous studies. For example, Yoon Wanjung [4] and Yun et al. [14] found no significant association between USC type and smoking behavior. This discrepancy may be due to differences in how USC types were classified. The earlier studies categorized USC based solely on the presence or absence of a usual hospital and physician, resulting in three USC types. In contrast, the present study differentiated USC types by whether a usual physician provided comprehensiveness and/or coordination, resulting in five distinct types [14-15]. These findings imply that, in addition to the primary care attribute of continuity, having a usual source of care that also provides comprehensiveness and coordination may play a meaningful role in promoting healthier lifestyle behaviors such as smoking cessation.

A second reason why this study, unlike previous research, found a significant association between having a USC and smoking cessation may be attributed to differences in the timing of data collection. The data used in this study were from 2021, after the implementation of key government health initiatives—namely, the National Smoking Cessation Support Program and the Primary Care Chronic Disease Management Program. These programs introduced incentives for both healthcare providers and patients to support smoking cessation, and their impact is likely reflected in this study’s results. In contrast, prior studies relied on data collected before 2015, a period when these initiatives had not yet been launched. Since 2015, the Korean government has used revenue from increased tobacco taxes to fund smoking cessation services, enabling smokers to receive formal counseling and treatment through medical institutions [22]. In September 2016, the government further expanded support through a pilot program offering reimbursement incentives for chronic disease management, including smoking cessation interventions, on a national scale. As such, the absence of these policy incentives in the earlier data may explain why previous studies failed to find a significant link between USC and smoking behavior. These findings highlight the importance of integrating incentive structures into public health policy, suggesting that ownership of a usual source of care combined with behavioral incentives could be a more effective strategy for improving health behaviors such as smoking cessation.

Beyond smoking cessation, this study also found that having a USC was associated with alcohol abstinence and engagement in physical activity. Specifically, individuals who had either a USC consisting of only a healthcare facility or a USC physician with either comprehensiveness or coordination were 1.16 times more likely to abstain from alcohol, and 1.24 times and 1.23 times more likely, respectively, to engage in regular physical activity, compared to those without a USC. However, the odds ratios for alcohol abstinence and physical activity were lower than those observed for smoking cessation. In fact, for some USC types, the odds ratio for alcohol abstinence was less than 1, indicating no positive association. Some prior research has examined the impact of a USC on healthy behaviors in the general population, with somewhat mixed results. Findings consistently show no significant association between USC and smoking cessation [14,16,25], whereas others found a positive association between USC and physical activity [14] or alcohol consumption [16]. Prior studies focusing on middle-aged and older adults have also shown a positive association between USC and physical activity, but not with alcohol consumption [14]. One possible explanation for the weaker associations between USC and alcohol abstinence or physical activity, compared to smoking cessation, could be the lack of strong policy-driven incentives targeting alcohol reduction and exercise promotion. While smoking cessation has been actively supported through government programs and financial incentives, similar support mechanisms for alcohol abstinence and physical activity have been less actively implemented.

A key limitation of this study is that it utilized cross-sectional data, which makes it difficult to establish a causal relationship between having a USC and maintaining healthy lifestyle behaviors. In other words, there is a possibility of reverse causality, wherein individuals who already practice healthy behaviors may be more likely to have a USC. For example, the non-smoking and non-drinking groups are likely to include a larger proportion of older adults, who also tend to have higher rates of USC ownership. Conversely, smokers and monthly drinkers—who tend to be younger—are more likely to lack USC. Although this study employed a multivariate regression model that adjusted for age and presence of chronic disease—both of which can influence USC ownership—this observational design cannot fully disentangle whether healthy behaviors influence USC ownership or vice versa. Therefore, the findings should be interpreted as associational rather than causal, and future longitudinal research is needed to clarify the directionality of this relationship.

Conclusions

In Korea, following a tobacco tax hike in 2015, the government began implementing smoking cessation support policies in earnest. Starting in 2016, a pilot project for chronic disease management in primary care was introduced, along with strengthened incentives for both patients and healthcare providers to promote healthier behaviors. This study demonstrates that having a USC with core primary care functions—namely comprehensiveness or coordination—is significantly associated with healthier behaviors such as smoking cessation, alcohol abstinence, and physical activity. In particular, the impact was strongest for smoking cessation, likely reflecting the influence of recent national health policies and incentive programs. The findings suggest that enhancing not only access to USC but also the quality and functionality of primary care may be a critical strategy for improving population health behaviors.

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