Background
Rapid urbanization and globalization has led to a marked increase in non-communicable diseases (NCDs) around the world [
1]. As the pathological processes linked to NCD may take years to develop, the use of preventive medicine to target risk factors during the pre-symptomatic period might prevent the development of cardiovascular disease (CVD) or other chronic diseases. Continuous management of subclinical pathology requires very safe agents to be regularly taken for an individual’s lifetime. The use of herbal medicine either for primary prevention or as complementary and alternative medicine for CVD risk factors such as hypertension or diabetes and other NCD is thus of increasing interest to the public and the medical community [
2].
The World Health Organization (WHO) estimated that 70–80% of populations from developing countries use herbal and traditional medicine (HTM) as the primary method for health care needs, and HTM use has also been extensively embraced in Western countries [
3]. Despite the widespread use for centuries, HTM is often approached with skepticism by the medical community [
4] and evidence-based studies of the efficacy and safety of HTM in the management of chronic diseases are still limited [
2]. At present, few large population surveys have examined HTM use in conjunction with laboratory and clinical data. The relationship between HTM consumption and the level of therapeutic control of CVD risk factors in the general population is still relatively unknown. HTM may improve the control of CVD risk factors either through direct pharmacological effects and HTM users might be more proactive to health risk modifications. On the other hand, HTM has also been associated with worsening kidney function [
5] or liver toxicity [
6].
In 2011, Thailand was reclassified by the World Bank from a lower-middle income to a higher-middle-income country. Along with the economic transition, the prevalence of CVD and related risk factors have increased markedly [
7]. Self-prescribed herbal medicine is common among patients attending healthcare facilities in Southeast Asia, [
8,
9] but there is limited information on the relationship of HTM usage with chronic diseases in the Thai community at large. The main aims of this study were to examine the prevalence and factors associated with HTM use in a Thai worker population. In addition, we will explore the relationship between HTM use and therapeutic control of CVD risk factors, and also document the most common types of HTM used in various chronic diseases.
Discussion
In this study, we found that 33% of a Thai worker population used HTM. Age < 50 years, female gender, self-reported history of diabetes, liver disease, cancer, dyslipidemia, and alcohol use were independently associated with HTM use. HTM consumption increased in proportion to the numbers of self-reported chronic disease factors. There were no differences in the therapeutic control of CV risk factors between HTM users and non-users. The most commonly used HTM was turmeric.
The reported prevalence of traditional medicine users in Southeast Asia varied widely from 55% in Singapore to 2% in Indonesia [
9]. In Thailand, data from National Health Survey in 2014 showed that 21.9% of Thai population had used HTM [
14]. On the other hand, smaller surveys involving a few hundred subjects showed that 29 to 54% were using HTM [
15,
16]. In our study of over 6000 subjects, we found a high percentage of HTM usage in a Thai worker population (33%) similar to previous smaller local surveys. The differences between various studies may be partially explained by differences in the reference period (ever used versus past year use) and inclusion of other health practices such as Thai massage, and meditation in the survey.
Chronic illnesses has been associated with higher HTM use in Western populations [
17]. Surveys from Thai outpatient clinics showed that between 35 and 60% of patients with chronic diseases used HTM [
8‐
19]. Our study of community -based workers demonstrated that chronic disease or known CVD risk factors appear to be associated with HTM use in a Thai general population, although HTM use was still quite high (30%) even in those without known pre-existing conditions. Obesity is also associated with higher HTM use in our study. Obesity is often associated with multiple risk factors for CVD and predisposes to many chronic diseases. Given high toxicities or lack efficacy of Western medications on the treatment of obesity, there has been considerable interests in the use of HTM to assist weight loss or prevent long term consequences of obesity [
20]. Our study also showed that current alcohol intake was associated with HTM use. This is similar to results from the US, where drinkers were more likely to have used HTM, compared to lifetime teetotalers [
21]. The relationship between alcohol and HTM use is complex, as many factors in life could influence both the use of HTM and alcohol consumption such as partner strain, pain and mental disorders such as major depression and panic disorders.
Although HTM are widely used in patients with established CVD, [
22] the relationship of HTM use with CV risk factor control in the general population is unknown. We did not observe any differences in BP level or laboratory parameters between HTM users and non-users. Moreover, in subjects with known self-reported conditions, HTM use was not associated with better therapeutic control. These findings do not exclude potential benefits of specific HTM on CVD risk factors. The pharmacologic impact of specific HTMs might not be apparent due to the heterogeneity in preparations used in our study. Several factors may also affect control of CV risk factors including the pre-existing severity of the risk factors prior to HTM use which are not known. In addition, there is some evidence to suggest that rather than leading to an improved life-style, some HTM users may paradoxically have reduced compliance of prescribed medications because of a false sense of security of therapeutic control [
22].
Most of the HTMs in our top ten list has been shown to have potential health benefits. In Thailand, turmeric is a commonly used culinary compound, listed in Thai National List of Essential Medicines as anti- flatulence agent [
23]. Turmeric contains a variety of curcumins which have been shown in experimental studies to have lipid lowering, anti-oxidant, anticancer properties associated with minimum toxicity [
24,
25]. Cinnamon was the most common HTM in subjects with self-reported diabetes. Several studies have shown that cinnamon may improve glycemic control in diabetics [
26]. Of interest, some types of cinnamon contain coumarin, which may interfere with concomitant use of anticoagulants. Garlic is the most commonly used drug in subjects with self-reported hypertension. Garlic may help to reduce blood pressure, cholesterol, and inhibit platelet aggregation, although different garlic preparations may have variable effectiveness on blood pressure [
27,
28]. Lingzhi mushroom possess immunomodulation and antioxidant properties as well as inhibitory effects on angiotensin converting enzyme [
29]. These properties may account for their popularity in subjects with CKD [
18] and cancer. The benefits of Lingzhi mushroom on quality of life has been shown in cancer patients [
30]. Kariyat was used in subjects with self-reported liver disease and those with severe liver enzyme abnormality. Protective effects of Kariyat on liver disease has been shown in vitro and in vivo [
31]. Of interest, Kariyat is used by Khmer traditional healers in Cambodia for treatment of liver disease perhaps reflecting common regional traditional practices [
32]. Kariyat is also widely promoted for use as a therapy of common cold and diarrhea [
33] which may account for its common usage in Thailand [
34]. Though considered safe, serious allergic effects to Kariyat have been reported [
35].
For some commonly used HTM, more studies are necessary to demonstrate potential health benefits. Black ginger (
Kaempferia parviflora) has been used in Southeast Asia for centuries to improve physical work capacity and as an aphrodisiac. It has been selected as a champion herbal product to generate income in Thailand. A recent systematic review, however, failed to find conclusive evidence to support the benefits of
Kaempferia parviflora [
36]. Leaves, pod, seeds and oils from drumstick tree (
Moringa oleifera) possess pharmacological activity based on pre-clinical studies in chronic diseases such as dyslipidemia, diabetes and hypertension [
37]. Although the use of drum stick tree has recently been popularized in Thailand, there has been no comprehensive study of their pharmacological effects in humans [
37,
38].
In Thailand, HTM is available mostly as traditional drugs or formulations, modified traditional drugs in modern dosage forms, e.g. capsules or tablets or as phytopharmaceuticals, which are composed of standardized active plant materials in the form of semi-purified compounds. In practice, the consumers do not differentiate between the different types of preparations or dosage and culinary herbs taken in higher quantities are often included as HTM. Mixed botanical preparations was listed by many HTM users. Typically, these preparations contain a wide-spectrum of herbs and the contents are not known by the consumers as the labelling of all ingredients are not legally enforced. Indeed, the majority of users were not able to list the HTM, they consumed. Although we did not determine the sources of HTM in this study, other studies in diabetic [
19] and CKD patients [
18] showed that although a proportion of HTM are prescribed by licensed traditional medicine practitioners, most HTM use in Thailand is self-prescribed with folk remedy shops, direct sale, markets or family being the commonest sources. Under these circumstances which may be unregulated, the subjects often do not know the types of HTM they consumed.
HTM especially the use of aristolochic acid in Chinese traditional medicine use has been shown to be associated with CKD [
5]. Less frequent use of aristolochic acid might account for the lack of association of HTM use with CKD in our subjects. Overall, we did not demonstrate any association between abnormal liver function tests and HTM consumption. However, heart-leaved moonseed (believed to have important immune-modulation properties was among the most commonly used HTM in those with mildly elevated liver function tests. This drug has been reported to cause toxic hepatitis [
39]. Thus, vigilance may be necessary with its use.
This study has several implications. First, the high prevalence of HTM use in the community should raise the vigilance of the Thai healthcare professionals to inquire about HTM use in their patients. Medical practitioners are often unaware of HTM use, either due to the patients’ reluctance to disclose HTM use, or because the physicians do not ask [
19]. HTM may interact with prescribed medications leading to loss of efficacy or increased adverse effects. The likelihood of herb-drug interactions may be higher in the 20% of subjects who take more than one type of HTM [
22]. In addition, compliance of prescribed drugs need to be specifically addressed among HTM users. Secondly, there is a special concern regarding the lack of knowledge regarding the types of HTM consumed. Regulatory requirements to certify HTM preparations and control the distribution of products with unknown biological effects are necessary to minimize potential harm [
3]. Meanwhile, patients should be educated to observe the safety and efficacy of OTC HTMs such as turmeric, kariyat by their own as distribution channel of OTC as HTM quality may not be regulated by health professionals. Finally, many of the commonly used HTM possess pharmacologic effects which should be explored further in the context of clinical trials and the long term side-effects recorded in registries. All these issues are especially important now as the Thai Government has new policies to develop of the Thai HTM industry as a key economic driver, which will likely increase the use of HTM.
The strengths of our study are that this is one of the largest study on HTM consumption in Southeast Asia and one of the few studies to evaluate the relationship between HTM consumption with chronic diseases and CV risk factor control using both clinical and laboratory parameters in community-based subjects. Unlike most previous studies, which have generally been in the form of questionnaires, our data was obtained by trained medical personnel with special emphasis on chronic disease detection employing standardized laboratory procedures. There are several limitations of the study. This was a cross-sectional analysis, and causal relationship between HTM use and disease status or therapeutic control cannot be established. Data was not available on the dose or duration of HTM use, which would be important in defining HTM exposure. In addition, we did not have data on the reason or expectations of subjects for using HTM. Therefore, our study probably reflects the HTM prevalence and consumption behavior rather than the effects of specific HTM on CVD control. The list of HTM was by obtained by recall and many people did not list the HTM used. Thus the data represented a general pattern of HTM prevalence rather than a formal assessment of specific HTM use. Nonetheless, the common HTM identified in this community-based study are similar to other studies from Thai outpatient clinics [
18,
19]. Finally, while our findings should be generally applicable to the Thai community, our studied subjects had a higher proportion of males and consisted of a worker population that may differ slightly from the Thai population as a whole. Although EGAT employees come from all regions of Thailand and cover a wide-range of demographic backgrounds, the socio-economic status of EGAT employees is probably better than some of the most severely economically disadvantaged Thais, and the study did not include the severely ill or disabled subjects excluded from employment [
10]. Nonetheless, the prevalence of CVD risk factors found in our study subjects are comparable to those found in nationally representative surveys [
40].
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