Abstract
Supplement use is influenced by personal factors such as sex, knowledge, health status, and sociocultural factors. Korean women with musculoskeletal disease commonly use dietary supplements for purposes such as symptom relief. This study aimed to identify the differences in demographics, health status, and functional health literacy depending on the use of dietary supplements in Korean women with musculoskeletal disease. A cross-sectional study and secondary data analysis were designed using a representative, multilevel stratified cluster sample from the 8th wave (2019) of the National Health and Nutrition Examination Survey, a national statistical survey encompassing health status, health behaviors, and food and nutrient consumption. Data on 804 women aged 20 years or older with musculoskeletal disease were included. A complex samples χ2-test was conducted to compare all variables such as demographics, health status, and functional health literacy. As results, significant differences were found between the dietary supplement user and non-user groups in terms of age (χ2 = 12.21, P = .009), type of health insurance (χ2 = 4.01, P = .049), education level (χ2 = 42.86, P < .001), and presence of diabetes mellitus (χ2 = 9.16, P = .005). Functional health literacy was higher in the user group than in the non-user group (χ² = 5.48, P = .050). We found that younger individuals with health insurance, higher educational levels, and functional health literacy, and who do not have diabetes are likely to use dietary supplements. Healthcare providers should continue to monitor the use of dietary supplements among women with musculoskeletal diseases to ensure their safe and effective use.
Introduction
Musculoskeletal disorders such as arthritis are a major cause of long-term disease and disability worldwide. Women are more likely to have musculoskeletal disease than men, and the prevalence of these disorders increases with age.1,2 Approximately 73% of women aged ≥65 years’ experience one or more types of musculoskeletal disease, such as osteoporosis or rheumatoid arthritis, during their lifetime. 3 As discomfort from musculoskeletal disorders directly affects daily life, healthcare providers should pay close attention to symptom management behaviors. Women with musculoskeletal disease often use food supplements to alleviate symptoms such as pain and manage their daily health. 4
Dietary supplements (hereafter referred to as supplements) facilitate self-medication, defined as acquiring and using medication without a medical prescription. 4 Generally, a food product that a consumer can select and purchase from a pharmacy or retail store without a prescription is considered to be of proven efficacy and safety. 5 However, supplements are not always safe or beneficial and can pose unexpected health risks.4,5 According to the Centers for Disease Control and Prevention in the US, 76% of individuals aged ≥60 years take at least 2 non-prescription drugs, and 71% of the Danish population also takes supplements. 6 A survey in the Republic of Korea (Korea hereafter) indicated that approximately 64% of adults with chronic health conditions use supplements, with a higher proportion of women (vs men) using them. 4 Among these supplements, nutritional supplements such as multivitamins are the most commonly used in Korea. 7
Previous studies have indicated that supplement use is influenced by personal factors such as sex, knowledge, health status, and sociocultural factors.4,5,8 The use of supplements has been linked to being a woman, being older, having a higher educational level, certain health conditions, and having a lack of health literacy (eg, understanding of supplements and food labels).4,5,9 -11 In Korea, older women with chronic conditions are more likely to have lower educational levels and poor functional health literacy, which can interfere with the proper use of supplements.5,12 However, findings in Korea are not always consistent.9,10 For example, a study on diabetes found that functional health literacy did not affect prediabetes among Korean women. 9 This discrepancy may be because Korean women, despite having lower educational levels than men, demonstrate higher functional health literacy as they often take the lead in managing family health, including through cooking. 13 Nevertheless, higher supplement use in Germany was reported among older women who did not understand the supplement leaflets. 14 These differences among countries suggest that cultural and medical environmental factors influence supplement use.
In 2013, the Korean government implemented a policy that allowed the sale of drugs and food supplements outside pharmacies, making these products readily available. 4 Studies have shown that people with chronic diseases, such as musculoskeletal disease, often struggle to understand medication-related information, including medicine information leaflets and supplement labels.4,7,9,13 Nearly 10 years later, there is a need for further research on supplement use because of the abovementioned inconsistent findings among individuals with chronic conditions.
Therefore, this study aimed to identify the differences in general characteristics and health behavior factors based on supplement use. Additionally, we investigated the factors associated with supplement use in adult Korean women with musculoskeletal disorders.
Methods
Study Design
A descriptive cross-sectional study was conducted using data from the 8th Korea National Health and Nutrition Examination Survey (KNHANES-VIII) to identify the factors associated with supplement use.
Data Source and Participants
KNHANES has been ongoing for over 20 years. Public-private partnerships were formed with relevant academic societies to maintain quality assurance and control expertise. 15 Approximately 30 expert advisory committees comprising over 180 experts participated in quality assurance and control. 15 Specifically, full-time field staff training, guideline development, and field quality control tasks were performed in collaboration with relevant academic societies. Collaboration with academic societies was formalized through memoranda of understanding and research contracts in quality control. The quality control details are publicly available on the KNHANES homepage (https://knhanes.kdca.go.kr). 15
The KNHANES comprises screening, health, and nutritional surveys. It is a legal survey that calculates statistics with national representation and reliability regarding the people’s health level, health-related awareness and behavior, and the actual state of food and nutrition intake. The KNHANES is a publicly available dataset provided by the Korea Disease Control and Prevention Agency (KDPCA). 15 The KDPCA provides only de-identified data that cannot be used to infer individuals from the survey data in compliance with the Personal Information Protection Act and the Statistics Act (The Korea National Health and Nutrition Examination Survey Raw Data Use Guidelines VIII-1 (2019), 2021, Korea Disease Control and Prevention Agency, p. 5). All data are de-identified to protect participant confidentiality. In particular, statistical data are used as indicators for goal setting and evaluation of the Comprehensive National Health Promotion Plan. Moreover, they are used as basic data for health policy establishment and evaluation, such as the development of health promotion programs.
The KNHANES can be generalized to the entire population using the multilevel stratified colony sampling method. In the first year of the 8th period (2019), 192 survey districts and 25 households were selected as samples. The extraction frame was stratified based on city/province, housing type (general house or apartment), residential area ratio, age of the household head, and ratio of single-person households, which were used as implicit stratification criteria.
Of the 8110 in the KNHANES-VIII conducted in 2019, 881 women aged >20 had musculoskeletal disorders (at least 1 had osteoarthritis, rheumatoid arthritis, osteoporosis, and gout each). Of these 881 women, the 804 people who answered whether they took dietary supplements continuously for 2 weeks or more during the past year were included in this study (see Figure 1).
Participants’ selection process.
Measurements
Supplement Use
Those who used supplements for more than 2 weeks during the past year were surveyed and asked to respond “yes” or “no.”
General Characteristics
Age (≤64, 65-74, or ≥75 years), types of health insurance (national health insurance or medical benefits), education level (≤elementary school, middle school, high school, or ≥college), living with spouse (no or yes), hypertension (no or yes), diabetes (no or yes) were surveyed.
Health Behavior and Symptom-Related Factors
Sleeping difficulties—categorized as not at all, little, a lot, or unable to sleep—are an item in the Health-related Quality of Life Instrument with 8 Items (HINT-8) that consist of vitality, climbing stairs, pain, depression, working, happiness, memory, and sleep. 16 Pain, an item in HINT-8, was categorized as none at all, slight, severe, or excruciating. Participants’ alcohol consumption during the past year was categorized as not at all, less than once a month, or more than once a month. Physical activity was defined as moderate physical activity for at least 2 h and 30 min, high-intensity physical activity for at least 1 h and 15 min, or a combination of moderate- and high-intensity physical activity (1 min for high-intensity and 2 min for medium intensity) per week. Weight control efforts were categorized into reduced, maintained, increased, or no effort over the past year. Body-mass index was categorized as <22.9 or ≥23 kg/m2, based on a study classified according to Asian standards. 10 Depressive symptoms were categorized as no or yes, indicating whether there was a feeling of depression for more than 2 weeks. Subjective health status was classified as good, normal, or bad based on subjective thoughts about health.
Functional Health Literacy
Functional health literacy was measured using 2 questions. The questions were, “Do you read nutrition labels when buying or choosing processed foods?” and “Does the content of nutrition labels influence your food choices?” and the answers were “yes” or “no.” Participants were asked if they utilized nutrition fact labels by responding “yes” or “no.” They also answered “yes” or “no” to determine whether the nutrition labeling influenced their food choices. Furthermore, the question, “What nutrients are you interested in?” has answers such as calories or carbohydrates or sugars or proteins or fat or saturated fat or trans-fat or cholesterol or sodium. Nutrition labels’ nutrients of interest to users were categorized into 9 groups: calories, carbohydrates, sugars, proteins, fat, saturated fat, trans fat, cholesterol, and sodium.
Ethical Considerations
The survey procedure was approved by the Research Ethics Review Committee of the Korea Centers for Disease Control and Prevention (2018-01-03-C-A). In compliance with the Personal Information Protection Act and Statistical Act, the Korea Centers for Disease Control and Prevention provides only de-identified data so that individuals cannot be recognized from the survey data. This study was approved by downloading raw data from the Korea Centers for Disease Control and Prevention website. The Institutional Review Board of C-National University (Institutional Review Board No. 202408-SB-112-01) approved this study protocol.
Statistical Analysis
After generating a complex sample plan file, analysis was performed by assigning weights using IBM SPSS 25.0. Complex sample analysis can reduce the hidden sampling bias or errors because complex sample surveys identify and collect data from population units using multiple selection steps. Complex samples χ2-test was then conducted to compare the weighted percentage of all variables. Variables significantly associated with functional health literacy in the χ2-test were entered into a logistics analysis. Logistic regression is a statistical method used to estimate the probability of an event occurring—such as voting or not voting—based on a given dataset of independent variables. 17 Since the outcome represents a probability, the dependent variable is bounded between 0 and 1. Logistics analysis in this study examined the association between health literacy and the supplement user and non-user group variables. The significance level was set at .05.
Results
General Characteristics and Functional Health Literacy of Supplement User and Non-User Groups
Among the weighted n = 804, the prevalence of supplement use was 65.3% (weighted n = 525).
Significant differences were found between the 2 groups in age (χ2 = 12.21, P = .009), type of health insurance (χ2 = 4.01, P = .049), educational level (χ2 = 42.86, P < .001), and having diabetes mellitus (χ2 = 9.16, P = .005). The supplement user group had a significantly higher proportion of those aged <64 years, having national health insurance, and having college-level education or higher than the non-user group. Moreover, there was a higher proportion of nutrition fact-label users than the non-supply group (Table 1).
Comparisons of Health Behaviors and Symptom-Related Factors Between the Groups (Weighted N = 804).
n = number.
Significant results with P
Table 1 presents the distribution of health behaviors and symptom-related factors of the supplement user and non-user groups. Physical activity (χ2 = 12.72, P = .004) and subjective health status (χ2 = 10.94, P = .015) differed significantly between the 2 groups. More women in the supplement user group engaged in physical activity and answered that they were “healthy” compared with the non-user group.
Comparison of Functional Health Literacy and Interest Nutrients in Nutrition Fact Label Users
Factors related to functional health literacy were analyzed for the 420 participants who responded “yes” to health literacy recognition. Of the total, 70.5% (weighted n = 296) were taking supplements, and 29.5% (weighted n = 124) were not. Moreover, 40.3% (weighted n = 105) had functional health literacy in the supplement user group (weighted n = 296), while 28.2% (weighted n = 30) had functional health literacy in the supplement non-user group. Thus, significant differences between groups were found regarding functional health literacy (χ2 = 5.48, P = .049; see Table 2). Among those with functional health literacy (n = 135), the nutrients of most interest were calories (23.7%), followed by sugars (13.3%), cholesterol (12.6%), and trans fat (11.1%).
Distribution of Functional Health Literacy Between the Groups (Weighted n = 420).
n = number.
Significant results with P
Factors Related to Functional Health Literacy Supplements User and Non-User Group
In the user group, functional health literacy was higher in the age group under 64 years (OR = 5.92, 95% CI = 2.91-12.02) and 65-74 years old (OR = 2.60, 95% CI = 1.42-4.77) compared to those over 75 years old. In addition, health literacy was lower among less than elementary school (OR = 0.05, 95% CI = 0.02-0.17) and middle school (OR = 0.13, 95% CI = 0.04-0.40) than college graduates or higher. In the non-user group, functional health literacy was higher in the age group under 64 years (OR = 5.60, 95% CI = 2.13-14.71) and 65-74 years old (OR = 4.17, 95% CI = 1.89-9.20) compared to those over 75 years old. Functional health literacy was lower among those less than in elementary school (OR = 0.12, 95% CI = 0.02-0.69) than among college graduates or higher. Moreover, individuals without diabetes mellitus recognized functional health literacy than those with diabetes mellitus (OR = 2.63, 95% CI = 1.14-6.04; see Table 3).
Odds Ratios for Having Functional Health Literacy (Weighted n = 135).
n = number; OR = odds ratio; CI = confidence interval.
Discussion
The investigation of the characteristics of supplement users and non-users among women aged >20 years with musculoskeletal disorders showed that supplement users tended to be younger, had health insurance, had a high level of education, and did not have diabetes.
These results showed a trend similar to and different from existing research results. The difference is that prior studies found older adults are more likely to use supplements compared to younger populations.4,5 This difference is often assumed to be due to young adults’ greater health awareness and proactive well-being approach. For instance, a study on supplement use in US adults found that supplement use was more prevalent among younger adults, who were often more aware of and influenced by health trends and marketing efforts to promote a healthy lifestyle.18,19 Health insurance status was also positively associated with supplement use. Individuals with health insurance are more likely to have regular access to healthcare professionals, who may recommend or prescribe supplements as part of a comprehensive health plan. 19 Research on ethnic diversity in supplement use has shown that insured individuals tend to engage more in preventive health behaviors, including supplements, owing to increased access to healthcare resources and information. 19 Education level and supplement use were consistent with the findings of this and previous studies. 18 In previous studies, a strong correlation was found between higher education levels and supplements.18 -21 Educated individuals are generally better informed about the potential benefits of supplements and are more likely to engage in health-promoting behaviors. Individuals with higher educational attainment were more probable to use supplements as part of their health maintenance routines.18,19
The percentage of women who reported engaging in physical activity, controlling their weight, and having “good” health status was higher among those who used supplements than those who did not in this study. Supplement users are often healthier and less likely to suffer from chronic conditions, such as diabetes. 22 This is partly because those without chronic conditions may be more inclined to use supplements as part of a preventative health strategy rather than to manage existing health issues.23,24 Previous studies reported that individuals who use supplements report better overall health and fewer chronic conditions.22 -24 Consistent with previous studies,22,23 this study found that using supplements is prudent in chronic diseases such as diabetes. However, in a longitudinal study by Hua et al., supplement users tended to have more comorbidities and were at higher risk of medication burden than non-users; supplement use was not associated with any mortality benefit among patients with diabetes. 23 Patients with chronic diseases may be influenced by the use of supplements based on information from social media or unreliable personal sources. 24 Therefore, continuous monitoring and education on this issue are necessary. In particular, for musculoskeletal diseases, for which a variety of medications are often taken to manage pain and improve physical function, it is crucial to exercise caution when using supplements.
Health literacy plays a crucial role in supplement use.21,25 It has been reported that individuals with high health literacy are more likely to use supplements appropriately because they can better evaluate the quality and reliability of health information.9,11 Conversely, low health literacy is associated with an increased likelihood of risky health behaviors, including improper use of supplements. 26 In women with musculoskeletal diseases, functional health literacy was higher in the supplement use group, particularly among those with a higher level of education, reflecting findings similar to those of previous studies.9,13,26 Healthcare providers play a key role in enhancing patients’ health literacy, particularly regarding the safe use of supplements. 27 Providers who actively educate their patients about the evidence-based use of supplements and clear communication can help bridge the gap in health and lead to better health outcomes. 27
In our study, supplement users demonstrated high levels of physical activity and weight control efforts. The relationship between physical activity and supplement use has been widely studied, demonstrating a clear connection between these 2 health behaviors. 28 Studies have shown that individuals with higher levels of education and socioeconomic status who are more likely to engage in regular physical activity also have a higher prevalence of supplement use. 28 This reflects a broader understanding of health and nutrition, where supplement use is considered part of a comprehensive approach to maintaining or improving physical health. Particularly among individuals with musculoskeletal conditions or those engaging in regular exercise, supplements such as glucosamine, chondroitin, and omega-3 fatty acids are frequently used to support joint health and reduce inflammation. 19 However, there was no information about which supplements the participants used in our study, so specific details are unknown. Still, the supplement users’ primary nutrients of concern were “calories” and “sugar.” These concerns are particularly important because excessive calorie and sugar consumption can lead to weight gain, which exacerbates joint stress and inflammation and worsens the symptoms of musculoskeletal conditions. 28
Significance
This study underscores the importance of considering demographic and socioeconomic factors, such as age, education, and health insurance, in understanding the supplement use of women with musculoskeletal conditions. These findings emphasize the need for healthcare providers to play a proactive role in educating patients about safe supplement use, especially for those with chronic diseases where inappropriate supplement use could lead to adverse outcomes. Additionally, this study highlighted the critical role of health literacy in ensuring that supplement use is safe and beneficial. By identifying calorie and sugar intake as primary concerns among supplement users, this study draws attention to the potential nutritional risks associated with supplement use, which could affect the management of musculoskeletal conditions. Overall, this study suggests that a comprehensive approach involving patient education and careful monitoring is essential for this population’s safe and effective use of supplements.
Limitations
The primary limitation of this study is the lack of specific information regarding the types of supplements used by participants. Without detailed data on the exact supplements consumed, it is challenging to fully understand the impact of supplement use on musculoskeletal and other health outcomes. Additionally, the study did not consider the dosage, duration, or frequency of supplement use, which are critical factors in assessing the effectiveness and safety of supplements. Another limitation is the potential for self-report bias, as data on supplement use, physical activity, and health status were likely collected through self-report questionnaires. This can lead to inaccuracies due to the over- or under-reporting of behaviors and health conditions. The study’s cross-sectional nature also limits its ability to establish causal relationships between supplement use and health outcomes, as it only provides a snapshot of the participants at a single point in time. Lastly, the study’s findings may not be generalizable to all populations, as it focused specifically on women aged ≥20 years with musculoskeletal conditions, and the results may differ for other demographic groups or men.
Conclusion
This study explored the characteristics of supplement users and non-users among women aged ≥20 years with musculoskeletal health problems. The findings revealed that supplement users were generally younger, had health insurance, had higher levels of education, and did not have diabetes. These results are different from those of previous studies, indicating that younger, more health-conscious individuals, particularly those with access to healthcare and higher education, are more likely to use supplements. Additionally, supplement users in this study were more physically active, engaged in more weight control efforts, and reported better overall health than non-users. The study also highlighted that supplement users tend to have higher functional health literacy, especially among those with higher education levels, influencing their ability to use supplements appropriately. However, future studies are needed to determine whether similar results are observed in men with similar musculoskeletal disorders and to include more detailed information on the supplements used.
Footnotes
Acknowledgements
None.
Author Contributions
Y.S. conceptualized and designed the study; M.K. conducted data analysis and interpretation; M.K. and Y.S. drafted the manuscript; Y.S. and S.A.K. reviewed and edited the manuscript for intellectual content. All authors have read and approved the final version of the manuscript.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The work was supported by the Chungnam National University (2024-0826-01).
Ethics Approval and Informed Consent
The Institutional Review Board of C-National University (Institutional Review Board No. 202408-SB-112-01) approved the study protocol for the analysis of KNHANES data on [August 21, 2024]. The KNHANES data collection was approved by the Korea Disease Control and Prevention Agency (KDCA) Research Ethics Review Committee (Approval No. 2018-01-03-C-A). The KNHANES data are publicly available and de-identified; therefore, no additional informed consent was required for this study.
