Cardiovascular diseases (CVDs), including coronary heart disease and stroke, are the leading cause of death in Korea and worldwide. Deaths caused by CVD account for 50.3% of total deaths due to occupational disease.1 In addition, the economic burden of workers’ compensation and welfare services, including all work-related diseases and industrial accidents, has increased. According to the Korea Occupational Safety and Health Agency (KOSHA), the amount of money spent by the Korean government for CVD compensation in 2008 was about 9.5% of the total compensation expenses in Korea.2,3
Occupational health professionals in Korea have attempted to decrease the incidence of CVD among workers by screening for risk factors, controlling lifestyle, and reducing job stress through education. However, in Korea, healthcare providers in charge of health management or health promotion programs for industrial workers have rarely been assigned to workplaces with fewer than 300 employees.4–6 Although the number of workers in small workplaces (ie, <50 employees) accounted for 82.3% of total industrial workers in Korea, occupational health nurses are available only to large-sized industries.3 All citizens in Korea are required to be enrolled in a national health insurance system, and this insurance covers workers and their dependents. Risk factors for CVD and other diseases can be screened through the biannual or annual medical examinations required for all insured workers.6 Employees who work in potentially harmful conditions (eg, places with dust, heavy metal or solvent poisoning, acid or base exposure, environments with loud noise) have a special evaluation every 6 to 12 months, whereas employees who work in less hazardous conditions participate in the required general health examinations. If a health examination indicates suspected disease, the worker would then have to undergo a specific examination to identify the disease. If the examination indicates the potential for a serious health condition (eg, hypertension or diabetes), workers need to have an annual check-up and obtain lifestyle modification advice through health counseling.
According to the KOSHA, CVD was the second most commonly diagnosed condition among workers after musculoskeletal disorders, with 67.8% of workers in small-sized industries in Korea being diagnosed with CVD. Because CVD was included as a category of compensable occupational diseases caused by overwork, the incidence rate of CVD as an occupational disease has increased.6 The KOSHA reported that 69% and 43% of workers of medium- and small-sized industries, respectively, reported a diagnosis of hypertension or diabetes.2,3 In addition, workers’ self-reported perception of CVD risk was low, particularly among blue-collar workers in small companies.7 In particular, previous studies supported that male workers are vulnerable to CVD risk. A study conducted with large-sized industry workers reported that 30% to 50% of Korean male workers currently smoked cigarettes and did not engage in any physical exercise.8 Furthermore, previous multicenter registry trials reported that the prevalence of acute myocardial infarction and ischemic cerebral infarction was higher in male than in female patients.9,10
The Framingham Risk Score (FRS) has been used widely in the assessment of CVD risk factors, despite some researchers’ concerns about its potential to overestimate risk.11 We have a guideline on CVD and cerebrovascular risk estimation for Korean workers developed by KOSHA that aimed to assess risk and focused on managing hypertension. Although the KOSHA guidelines have commonly been used in Korean workplaces, they have limited applicability to young workers because risk groups are not identified if people do not have hypertension, diabetes, heart disease, or target organ damage.12 Although there are some limitations in using the FRS in countries other than the United States and in adopting younger populations, the general FRS with summing major risk factors and considering interactions among variables can be a comparatively effective tool for assessing 10-year CVD risk.12,13
A primary purpose of this study was to characterize general CVD risk of heart disease or stroke in a sample of male workers. In addition, we examined the distribution of mean values of cardiovascular risk factors and lifestyle behaviors by age group, examined the relationship between subject characteristics and CVD risk groups, and identified predictors of those at high risk for CVD.
This study used a cross-sectional descriptive design. Routine health screening data were collected from workers in small-sized industries.
Sample and Data Collection
Before the study, we explained the purpose of the study to K Hospital, a representative healthcare center responsible for institutional health management, and received written approval from the head of the hospital. The study protocol was approved by the institutional review board of Chosun University, with which the principal investigator is affiliated (IRB-12-012).
Initially, we obtained health records for 32 414 workers in small-sized industries or companies having 300 or fewer employees from 2007 to 2011 by K Hospital in G City, South Korea. The health records included blood tests for lipid profiles, glucose, liver, and kidney function; lifestyle behaviors; and measurements of height, weight, and blood pressure. However, data obtained from 2007 to 2008 were deleted because of missing physiological data (eg, high-density lipoprotein [HDL] measurements). Among the collected health records, we chose the first registered data from various subjects at multiple time points. In addition, the data of female employees from 2009 to 2011 were excluded. Finally, the data from 12 933 male workers obtained from 2009 to 2011 were included in the analysis.
Demographic characteristics included age, occupational classification, past or current medical history, and family history of CVD. Occupational classification refers to the Korean Standard Classification of Occupation, which classifies workers into nonmanual and manual groups.14 Nonmanual workers include managers, professionals, and clerks. For the purposes of our study, we considered any office worker to be a nonmanual worker. Manual workers included those in transport-related (eg, bus or taxi driver) and production-related (eg, manufacturing) elementary occupations. Past or current medical history refers to whether subjects currently have hypertension, heart disease, dyslipidemia, or diabetes or have had these health concerns in the past, and family history of CVD refers to whether subjects had family members with hypertension, heart disease, dyslipidemia, or diabetes.
In addition, subjects provided self-report data regarding lifestyle and behavioral risk factors such as smoking, alcohol consumption, and physical activity. Smokers were defined as those who smoked currently or had ever smoked in the past. Information regarding alcohol consumption included the frequency and average amount of alcohol consumed at a single time. Heavy drinking was defined as 4 or more drinks per day or 14 or more drinks per week.15 The frequency of regular physical activity with moderate intensity also was self-reported.
Physiological risk factors, including total cholesterol, triglycerides (TG), HDL, fasting blood sugar (FBS), and blood pressure, were directly measured.
Each participant’s risk of having a CVD event such as stroke, heart failure, myocardial infarction, and coronary insufficiency within 10 years was calculated using general FRS by summing each factor’s score and its assessment criteria. General FRS assessment criteria include the following major risk variables: gender, age, total cholesterol, HDL, untreated systolic blood pressure (SBP), treated SBP, cigarette smoking, and diabetes.13
Individuals with FRS scores of 15 or higher were regarded as the high-risk group, with a possibility of CVD occurrence within 10 years of greater than 20%, whereas individuals with FRS scores of lower than 15 were the low risk group, with a possibility of CVD occurrence of 20% or less.16
All statistical analyses were performed using SPSS 22.0. Descriptive statistics were used to describe participant characteristics, physiological factors, and health behaviors. Independent t tests and χ2 tests were used to compare the characteristics of subjects with low and high CVD risk. Multiple logistic regression analysis was performed to determine which variables predicted groups at high and low risk for CVD.
Subjects’ mean (SD) age was 42.1 (9.20) years (range, 30–70 years), and 47.5% of the subjects were 30 to 39 years old (Table 1). With regard to occupational type, 83.5% of subjects were manufacturing workers. Of the participants, 29.8% had a body mass index (BMI) 25 kg/m2 or greater, which classified them as overweight, 50% were current cigarette smokers, and 24.1% answered that they did not exercise at all (ie, they were physically inactive). In addition, 32.4% of subjects were categorized as heavy consumers of alcohol (ie, ≥4 drinks per day or 14 drinks per week).
Figure 1 shows the age-specific prevalence of CVD risk factors. Diastolic blood pressure (F = 79.28), FBS (F = 122.87), SBP (F = 127.11), and BMI (χ2 = 146.51) were associated with advanced age (P < .001). However, the prevalence of current cigarette smoking (χ2 = 203.59), physical inactivity (χ2 = 135.94), and heavy alcohol consumption (χ2 = 114.52) was higher in younger subjects than in those in other age groups (P < .001).
Cardiovascular disease risk over the next 10 years was estimated using the FRS. The proportion of subjects in the high-risk group was 0.2%, 2.5%, 21.6%, and 48.5% for those aged 30 to 39, 40 to 49, 50 to 59, and 60 to 70 years, respectively (Figure 2).
Chi-square and independent t tests were used to examine statistical differences between the high- (>20%) and low-risk groups (Table 2). Subjects in the high-risk group were more likely than those in the low-risk group to be older, have an increased likelihood of a BMI of 25 kg/m2 or greater, and have higher serum TG level. They were also less likely to exercise and more likely to have a history of stroke or heart disease. With regard to occupational type, bus or taxi drivers were more likely to be in the high-risk group.
Multiple logistic regression analysis was performed to determine which factors predicted the 10-year CVD risk estimated by general FRS. Significantly associated variables found using bivariate analyses and from the literature review were entered into the regression model. After adjusting for age, occupation as a bus or taxi driver, high TG level, being overweight, lack of physical activity, and heavy alcohol consumption were tested as predictors of CVD (Table 3). Among the 3 occupational groups, the mean (SD) FRS value for manufacturing workers was lowest (6.2 [4.7]), and this group was regarded as the reference group. The odds ratio for CVD risk was 1.38 (95% confidence interval [CI], 1.14–1.65) for bus or taxi drivers compared with manufacturing workers. The adjusted odds ratios of high CVD risk were 1.51 (95% CI, 1.51–2.19) for subjects with a BMI of 25 kg/m2 or greater, 1.28 (95% CI, 1.03–1.57) for physically inactive subjects, and 1.83 (95% CI, 1.52–2.20) for subjects who reported heavy alcohol consumption.
In the present study, 10-year CVD risk estimation using the FRS showed that 7.1% of male workers were in the high-risk group. This rate is similar to that in a study for employees of the Korean National Health and Nutrition Examination Survey data, which showed that 7.3% of male manufacturing workers were identified as members of the high CVD risk group.17 In a study that applied the FRS to 1781 male workers a large steel company in Korea, out of 46% of those older than 50 years, 8.9% were identified as members of the high-risk group.12 The different ages and work sectors of subjects might account for the difference between these results and the findings of the present study. Male subjects in the present study were comparatively younger, whereas 46% of the subjects in the study conducted in the steel company were in their 50s. When examined by age, 14.4% of those 55 years or older belonged to the high CVD risk group, whereas only 1.9% of those younger than 55 years belonged to this group. In addition, this finding is supported by the results of the Korean National Health and Nutrition Examination Survey18 and the US National Health and Nutrition Examination Survey (NHANES),19 which suggested that CVD risk increases with age. However, direct comparisons of the findings from the current study with those of the Korean and US NHANES are limited because NHANES data included the entire population and subjects’ occupational background was not considered.
In addition, some physiological variables worsened with advanced age. Mean values of FBS, SBP, and diastolic blood pressure increased with age. In contrast, subjects who were current cigarette smokers, physically inactive, and heavy consumers of alcohol were more likely to be in their 30s. Notably, in the present study, 50% of male workers currently smoked cigarettes and 55.6% of those in their 30s were current cigarette smokers. This finding is consistent with the result of a national survey in Korea conducted in 2010, which suggested that physical inactivity was high in young male adults and more prevalent in those between the ages of 30 and 39 years.18 In addition, in the present study, 93.7% of workers in their 30s were manufacturing workers. This is consistent with studies in both Korea and Sweden that showed that the smoking rate of manual workers was higher than that of nonmanual workers20 and is consistent with a Swedish study that showed that the smoking rate in manual workers was higher than that in nonmanual workers.21 These results are also similar to those of a study in Japan that suggested that workers who were younger and employed by small-sized enterprises were more vulnerable to smoking than were their counterparts.22 Therefore, effective smoking cessation education programs that promote increased physical activity should be developed to target manual workers in the manufacturing workplace. Further research is needed to better understand risk factors for younger workers.
In this study, subject occupation type was a predictor of CVD risk. Subjects who engaged in driving work were 1.38 times more likely than manufacturing workers to have a 10-year high risk for CVD. This result conflicts with the findings of previous studies that found that workers who performed manual labor had an increased risk of CVD compared with office workers or drivers.17,23,24 This discrepancy might be related to the younger age of subjects in the present study. As previously mentioned, 53.3% of manufacturing workers were in their 30s. Accordingly, preventive education on lifestyle change to reduce CVD risk should be targeted for bus or taxi drivers. In addition, early intervention on lifestyle modification for younger workers is needed to target CVD prevention.
In our study, overweight workers (those with a BMI ≥25 kg/m2) were 1.5 times more likely and physically inactive workers were 1.3 times more likely to be at risk for CVD. This finding is supported by many previous studies about the relationship between CVD risk and overweight and/or physical inactivity, which have specifically identified being overweight as an important CVD risk factor.25–27 This finding was also similar to that of a study that demonstrated that the risk of developing hypertension and dyslipidemia increased with weight gain and decreased with weight loss.25 According to studies of the relationship between physical inactivity and CVD risk, large-scale epidemiological studies in Japan showed that subjects who engaged in physical activity for more than 5 h/wk were 50% less likely than less active subjects to be at high risk for CVD.26 A previous study also supported the idea that any type of physical activity (eg, running, weight training, walking) was associated with reduced CVD risk in men.27
Recently, the number of overweight and physically inactive young adults in Korea has increased. A study on nonsmoking Koreans reported that the percentage of men aged 30 to 39 years with a BMI greater than 25 kg/m2 has increased from 35% in 2000 to 42.3% in 2010 and 41.2% of men aged 40 to 49 years had a BMI greater than 25 kg/m2.28 They emphasized that being overweight had a greater impact on CVD mortality in younger men than in older men.28 Although responses in this study were self-reported, about 80% of subjects in the 30 to 49 years age range reported exercising less than 3 times per week. Moreover, consistent with previous research, subjects in the present study who were heavy alcohol drinkers were 1.83 times more likely to have a high CVD risk.8,29 Overweight and physical inactivity show a clear relationship with CVD. Given that a high percentage of Korean young adults are overweight and do not engage in physical activity, its members are at an increased risk for CVD and would benefit from weight reduction and exercise programs to reduce their risk. Therefore, industrial nurses should have health monitoring and counseling for young male workers, especially for those who are physically inactive and overweight.
This study has several limitations. First, data were collected from health examination records, which did not include sociodemographic variables (eg, education, economic status) that would have allowed for a comprehensive understanding of the workers. Second, the relationship between important work-related characteristics (eg, shift work, work hours, level of stress) and CVD risk was not examined. Third, information about subjects’ lifestyle risk factors was obtained based on self-report, which is subject to recall bias. Fourth, study data were collected from a specific region of Korea; therefore, the findings may not be representative of the entire population of small- to medium-sized industry workers in Korea. Fifth, we were not able to separate subjects based on whether they worked at places that addressed CVD prevention. Finally, we excluded data for female workers, and further study is needed on this population.
We found that 7.1% of male workers were part of the high-risk CVD group. Most workers were engaged in manufacturing work and most were in the range of 30 to 40 years old; thus, their CVD risk was relatively low. After adjusting for age, occupation type was identified as an important predictor of CVD, with bus or taxi drivers having greater vulnerability to CVD than manufacturing workers. In addition, BMI, physical inactivity, and heavy alcohol consumption also predicted high CVD risk. Young workers, in particular, were more likely to have lifestyle risk factors such as cigarette smoking and heavy alcohol consumption, which are common social behaviors in Korean society. These findings suggest that to reduce CVD risk, preventive education or work site health promotion programs are required for small-sized industrial workers who are heavy alcohol drinkers, physically inactive, overweight, and work as drivers. Especially, careful attention to lifestyle modification is needed for younger workers who are a latent risk group for the development of CVD.
What’s New and Important
- Young workers were more likely than old workers to have lifestyle risk factors such as cigarette smoking and alcohol drinking.
- When age was adjusted for, occupation type was identified as an important predicting factor of CVD, and drivers were more vulnerable to CVD risk.
- Work site health promotion programs are required for young workers and drivers who are latent risk groups for the development CVD, to control risk factors and lifestyle modification.
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