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Abstract
Objective The aim of the study was to estimate the prevalence and correlates of cardiovascular disease (ischaemic heart disease and/or stroke (IHDS)) in Mongolia.
Design Cross-sectional study.
Setting National community-based sample of people aged 15–69 years in Mongolia.
Participants 6654 people (15–69 years, mean 41.3) who participated in the 2019 Mongolia STEPS survey.
Primary and secondary outcome measures Self-reported prevalence of IHDS and biological and social covariates. Determinants of IHDS were estimated with logistic regression.
Results The prevalence of IHDS was 14.0%, 15.6% among women and 12.3% among men. Older age (45–69 years), being married or cohabiting, and urban residence were positively associated, and male sex was negatively associated, with IHDS. Additionally, experience of threats, hypertension, current tobacco use, passive smoking, sedentary behaviour and high physical activity were positively associated with IHDS.
Conclusions Almost one in seven people aged 15–69 years had IHDS in Mongolia. Several factors amenable to public health intervention for IHDS were identified, including experience of threats, hypertension, current tobacco use, passive smoking and sedentary behaviour.
- Ischaemic heart disease
- EPIDEMIOLOGY
- Public health
- Adult cardiology
Data availability statement
Data are available in a public, open access repository. The data source is publicly available at the WHO NCD Microdata Repository (URL: https://extranet.who.int/ncdsmicrodata/index.php/catalog).
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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STRENGTHS AND LIMITATIONS OF THIS STUDY
A large national sample of 6654 adolescents and adults in Mongolia was included.
Various social and biological determinants of cardiovascular disease (ischaemic heart disease and/or stroke (IHDS)) were included in the multivariable logistic regression model.
IHDS was measured by self-report, which may have biased the prevalence of IHDS.
Specific cardiovascular disease type and time since diagnosis were not evaluated.
Introduction
Globally, almost 18 million people died from cardiovascular diseases (CVDs) in 2019, representing 32% of all global deaths, of which more than three-quarters occurred in low-resourced countries.1 Half (49%) of the worldwide CVD burden in 2016 was attributed to ischaemic heart disease (IHD) and 33% to stroke.2 IHD and stroke showed the highest rates of death and morbidity in Mongolia.3 Two in five people (40%) died from CVDs in 2016 in Mongolia,4 and in 2018, IHD was 25.8, stroke was 20.4 and arterial hypertension was 0.8 per 10 000 population in men aged 45–64 years. Compared with the mortality rate of women at the same age group, rates of IHD, stroke and arterial hypertension were statistically significantly higher in men than in women.5 IHD affected 23.3% of inpatients in 2018 in Mongolia.5 In a national population survey among persons 40 years and older in Mongolia in 2009, the prevalence of IHD (diagnosed via Rose questionnaire and electrocardiography) was 16.2%.6 A review of epidemiological studies on IHD in Mongolia7 from 1970 to 2015 reports a high and increasing mortality rate of IHD in Mongolia. In further review, we could not find more recent national studies on IHD and/or stroke (IHDS) in Mongolia, a lower middle-income country in East Asia.
In urban–rural sites among middle and older aged persons in China, India and Iran, the prevalence rates of CVD by self-report were 7.4%, 2.7% and 6.0%, respectively.8 In national community-based studies in Nepal (24–64 years) and Malawi (18–69 years), 2% and 6.5% of the population had IHDS, respectively,9 10 and the prevalence rates of CVD by self-report were 3.3% and 3.6% in China (35–74 years),11 and 1.6% (35–74 years) in Thailand.11
Sociodemographic factors associated with CVD by self-report include increasing age,12–14 gender,12–15 urban residence,12 ethnicity,10 16 lower socioeconomic status13–15 17 18 and higher altitude region.7 Behavioural factors associated with CVD by self-report include tobacco consumption,18 19 physical inactivity,17 20 poor dietary behaviour, such as inadequate vegetable and fruit consumption,9 20 high salt intake21 22 and psychosocial distress,23–25 including suicidal behaviour,10 and having a history of childhood abuse.26 Biological factors associated with CVD include high blood pressure (BP),12 14 16 18–20 27 28 metabolic disorders, including diabetes,14 16–20 27 high body mass index17–20 27 and elevated cholesterol levels.12 15
The aim of this analysis was to estimate the prevalence and correlates of IHDS among people 15–69 years in a national population-based survey in Mongolia in 2019.
Methods
Sample and procedures
Secondary data from the 2019 cross-sectional STEPS surveys in Mongolia29 were analysed; the response rate was 98.1%.30 A multistage stratified sampling process (377 sampling units or clusters selected from 21 provinces and 9 districts of Ulaanbaatar) was carried out to randomly select participants from the target population. One individual within the age range of the survey (15–69 years) was randomly selected (using the Kish method) per household.30
Data collection followed the WHO three STEPS methodology: step 1: administration of a structured questionnaire (sociodemographic information, medical history, medication use and health risk behaviour); step 2: BP and anthropometric measurements and step 3: biochemical tests (blood glucose and blood lipids).30 Anthropometric measurements were taken using the Somatometre-Stanley 04-116 device and GIMA electronic scales.30 Of the three BP measurements using OMRON Model M5 automatic BP monitor,30 the last two readings were averaged.30 At the data collection site, total cholesterol (TC) and blood glucose were measured in peripheral (capillary) blood using dry chemical methods, biochemical analysis and automated analyser.30
Measures
Outcome measure: IHDS was assessed with the question, ‘Have you ever had a heart attack or chest pain from heart disease (angina) or a stroke (cerebrovascular accident or incident)?’ (No, Yes).30
Sociodemographic information comprised employment, marital and residence status, sex, age, education, number of adult (≥15 years) household members and ethnicity.30
Psychosocial stress included childhood physical abuse (‘Looking back on your childhood (before age 18 years), did a parent or adult in the household ever push, grab, shove, slap, hit, burn or throw something at you?’), childhood sexual abuse (‘Looking back on your childhood, did an adult or anyone at least 5 years older than you ever touch you sexually or try to make you touch them sexually or force you to have sex?’), adult sexual abuse (‘Since your 18th birthday, have you ever experienced a sex act involving either vaginal, oral or anal penetration against your will?’), experience of threats (‘In the past 12 months, have you been frightened for the safety of yourself or your family because of the anger or threats of another person(s)?’ and ‘During the past 12 months, have you had family problems or problems with your partner due to someone else’s drinking?’).30
Biological measures included measured central obesity (waist circumference ≥90 cm in men, ≥80 cm in women);31 hypertension/raised BP: systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg or where the participant is currently on antihypertensive medication;32 diabetes: fasting plasma glucose levels ≥7.0 mmol/L (126 mg/dL) or using insulin or oral hypoglycaemic drugs or having a history of diagnosis of diabetes;33 raised TC: fasting TC ≥5.0 mmol/L or currently on medication for raised cholesterol.33
Behavioural measures included current tobacco use, current heavy episodic drinking (six or more standard drinks in a single drinking occasion), exposure to secondary smoke, daily servings of fruit and vegetable intake, and sedentary behaviour (≥8 hours/day) and low, moderate and high physical activity based on the Global Physical Activity Questionnaire.34 Salt consumption was sourced from any always or often response from three questions: (1) ‘How often is salt, salty seasoning or a salty sauce added in cooking or preparing foods in your household?’, (2) ‘How often do you add salt or a salty sauce such as soy sauce to your food right before you eat it or as you are eating it?’, (3) ‘How often do you eat processed food high in salt? By processed food high in salt, I mean foods that have been altered from their natural state, such as packaged salty snacks, canned salty food including pickles and preserves, salty food prepared at a fast-food restaurant, cheese, bacon and processed meat’.30 Responses were dichotomised into 0 (never, rarely or sometimes) and 1 (often or always).
Data analysis
Statistical analyses were conducted with STATA software V.14.0 (Stata Corporation, College Station, Texas, USA), by considering the multistage sampling design. Analysis weights were calculated by taking the inverse of the probability of selection of each participant adjusted for differences in the age–sex composition of the sample population as compared with the target population.30 Unadjusted and adjusted logistic regression with variables statistically significant in the unadjusted models determined the prevalence of IHDS. The multivariable model included the following covariates: age, sex, marital status, residence status, region, threats, central obesity, hypertension, diabetes status, current tobacco use, passive smoking, sedentary behaviour, physical activity and salt consumption. The dependent variable was IHDS (yes or no). P<0.05 was accepted as statistically significant, and only complete cases were included in the analyses (missing values <0.2%). Svy commands in STATA were applied to adjust for sampling design, sampling weights and stratification, and the calculation of SEs. Taylor linearisation methods were used for variance estimation in which linear approximates (ie, the estimated variance) of a non-linear function (ie, the true variance) are derived by taking the first-order Taylor series of the approximation.
Patient and public involvement
Participants were not involved in the design of the study, recruitment or conduct of the study.
Results
Participant characteristics
In total, 6654 people (15–69 years, mean 41.3, SD=13.7) were included in the sample, and 55.4% were women. The prevalence of IHDS was 14.0%, 12.3% among men and 15.6% among women. Tables 1 and 2 provide further sample information regarding sociodemographic factors, psychosocial stress, biological measures and behavioural risk factors.
Sample and IHDS characteristics—social factors
Sample and IHDS characteristics—biological and behavioural factors
Associations with IHDS prevalence
In the final logistic regression model, older age (45–69 years) (adjusted OR (AOR): 1.68, 95% CI: 1.24 to 2.28), being married or cohabiting (AOR: 1.26, 95% CI: 1.01 to 1.58) and urban residence (AOR: 1.46, 95% CI: 1.13 to 1.88) were positively associated, and male sex (AOR: 0.66, 95% CI: 0.53 to 0.82) was negatively associated with IHDS. Furthermore, threats (AOR: 2.14, 95% CI: 1.58 to 3.18), hypertension (AOR: 1.38, 95% CI: 1.12 to 1.71), current tobacco use (AOR: 1.27, 95% CI: 1.01 to 1.58), passive smoking (AOR: 1.39, 95% CI: 1.13 to 1.69), sedentary behaviour (AOR: 1.48, 95% CI: 1.16 to 1.89) and high physical activity (AOR: 1.35, 95% CI: 1.07 to 1.71) were positively associated with IHDS. Frequent salt intake was marginally associated with IHDS (see table 3). The logistic regression on IHDS gave an adequate fit to the model (Hosmer-Lemeshow goodness-of-fit statistic=10.78 with 8 df, p=0.22).
Logistic regression with ischaemic heart disease and/or stroke (ICHS)
Discussion
In this national study among people 15–69 years in Mongolia, we found a high prevalence of IHDS (14.0%), and associated factors included female sex, older age, being married or cohabiting, urban residence, threats, hypertension, current tobacco use, passive smoking, sedentary behaviour and high physical activity. The found prevalence of IHDS in 2019 in Mongolia (14.0%, 15–69 years, 18.1%, ≥40–69 years) was higher than among persons 40 years and older in Mongolia in 2009 (16.2%),6 and 35–70 years in China (7.4%), India (2.7%) and Iran (6.0%),8 as well as in China (35–74 years; <3.5%),11 in Nepal (24–64 years; 2%),9 in Thailand (35–74 years; 1.6%)11 and in Malawi (18–69 years; 6.5%).10 The high prevalence of IHDS in Mongolia may be attributed to rapid urbanisation,7 including high rates of CVD risk factors (tobacco use, unhealthy diet, physical inactivity, harmful use of alcohol, overweight/obesity, raised BP, hyperglycaemia and hyperlipidaemia).3
In agreement with previous studies,12–15 we found an association between older age and urban residence with IHDS. Furthermore, female sex was positively associated with IHDS, which agrees with some studies, for example, in the USA13 and Iran,12 but not with some other studies, for example, in Greece14 and some African countries,15 and no sex difference was found in a 2009 community survey in Mongolia.6 Globally, the incidence of CVD among women is often lower than in men, and women have a higher mortality and worse prognosis after acute cardiovascular events than men.35 However, the mortality rate of IHD in Mongolia seems to be statistically significantly higher in men than in women.5 Participants from the Eastern region (23.3%) and Ulaanbaatar city (17.0%) had a higher prevalence of IHDS than participants from the Central region (8.9%). Regional differences were also found for the mortality rate due to CVDs in Mongolia, with higher rates in the Khangai, Central and Western regions, and lower in the Eastern region.5 Some of these regional differences may be attributed to altitude-related physical conditions,7 36 lifestyle, socioeconomic and healthcare system aspects.7 In a study in Singapore, ethnicity was associated with IHDS,16 while we did not find ethnic differences in the prevalence of IHDS. Some studies13–15 17 18 showed that lower socioeconomic status was associated with IHDS, while in our study, three or more adult household members (as a proxy for lower economic status), education and employment status were not statistically significantly associated with IHDS.
In line with previous research on psychosocial distress,10 23–26 this study showed that threats (a type of psychosocial stress) were positively associated with IHDS. Stress can increase the cerebrovascular disease risk by modulating symphaticomimetic activity, affecting the BP reactivity, cerebral endothelium, coagulation or heart rhythm.25 Sedentary behaviour and high physical activity were both found to be positively associated with IHDS in this study, while this is confirmed for sedentary behaviour in previous studies10 17 20 but not with high physical activity.17 20 Consistent with previous findings,14 19 21 22 this study showed an association between current tobacco use, passive smoking, frequent salt intake and IHDS. However, contrary to previous findings,9 20 poor diet (low vegetable/fruit intake) was not statistically significantly associated with IHDS. Tobacco use may have reduced in Mongolia due to tobacco demand-reduction measures and an increase in excise taxes on tobacco, however, more needs to be done to initiate and control tobacco use.37 38 The high salt consumption in the general population in Mongolia has been recognised and a national salt reduction strategy has been instituted to reduce salt intake.39 An unexpected finding was that participants with high physical activity had higher odds of IHDS. This result may be explained by people with IHDS having implemented physical activity advice by their health worker. People with IHDS in this study had been more likely advised to do physical activity by a healthcare provider (20.0%) than those without IHDS (16.5%; p<0.001).
Consistent with several studies,12 14 16–20 27 28 we found an association between hypertension and in unadjusted analysis between diabetes and IHDS. Contrary to previous studies,12 15 17 19 20 27 this STEPS survey did not find statistically significant associations between central obesity, raised TC and IHDS. It is possible that because of the high prevalence of central obesity (61.6%) and TC (31.0%), no statistically significant associations with IHDS were found. Although progress has been made in the reduction of CVD risk factors such as high BP, smoking and drug therapy counselling for high-risk persons,37 38 more needs to be done in controlling body weight, smoking cessation, healthy diets, and screening and control of high levels of BP and blood sugar,40 and consequently prevent and control CVD in Mongolia.
Study limitations include the self-report of IHDS, which, however, was found valid for epidemiological surveys.41 It is likely that people had died from CVD prior to the study, which highlights that our estimates are likely an underestimate.42 The 2019 STEPS survey in Mongolia used only one question on CVD, which hinders us to know the type of CVD and the length of suffering from specific CVDs. Moreover, the cross-sectional study design prevents drawing causative conclusions.
Conclusion
Almost one in seven people aged 15–69 years had IHDS in Mongolia. Several associated factors for IHDS, such as female sex, older age, being married or cohabiting, urban residence, threats, hypertension, current tobacco use, passive smoking and sedentary behaviour, were found that can help in targeting public health interventions.
Data availability statement
Data are available in a public, open access repository. The data source is publicly available at the WHO NCD Microdata Repository (URL: https://extranet.who.int/ncdsmicrodata/index.php/catalog).
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and was approved by the Ministry of Health Medical Ethical Committee, Mongolia (no approval number). Participants provided written informed consent.
Acknowledgments
This paper uses data from the 2019 Mongolia STEPS survey, implemented by the Ministry of Health and Public Health Institute with the support of the WHO.
References
Footnotes
Contributors SP and KP conceived and designed the research, performed statistical analysis, drafted the manuscript and made critical revision of the manuscript for key intellectual content. All authors read and approved the final version of the manuscript and have agreed to authorship and order of authorship for this manuscript. KP, the guarantor accepts full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.