Journal of Occupational & Environmental Medicine:
Cardiovascular Disease Morbidity in an Iowa Law Enforcement Cohort, Compared With the General Iowa Population
Franke, Warren D. PhD; Collins, Shannon A. MS; Hinz, Paul N. PhD
From the Department of Health and Human Performance (Dr Franke, Ms Collins) and the Department of Statistics (Dr Hinz), Iowa State University, Ames, Iowa.
Address correspondence to: Warren D. Franke, PhD, 247 Forker Building, Iowa State University, Ames, IA 50011.
It remains uncertain if law enforcement officers experience an elevated cardiovascular disease morbidity and, if so, whether their profession contributes to this incidence. Consequently, the self-reported incidence of cardiovascular disease (CVD) (coronary heart disease, myocardial infarction, stroke, coronary artery bypass graft surgery, angioplasty) and CVD risk factors (age, diabetes, elevated body mass index (≥ 27.8 kg · m-2), hypercholesterolemia, hypertension, tobacco use) in 232 male retirees, ≥ 55 years of age, from the Iowa Department of Public Safety were compared with 817 male Iowans of similar age. CVD incidence was higher in the law enforcement officers than the general population (31.5% vs 18.4%, P < 0.001). Using multiple logistic regression, factors found to be associated with CVD included the law enforcement profession (odds ratio [OR]= 2.34; 95% confidence interval [95% CI] = 1.5-3.6), hypercholesterolemia (OR= 2.37; 95% CI = 1.7-3.3); diabetes (OR = 2.22; 95% CI = 1.4-3.6), hypertension (OR = 1.79; 95% CI = 1.3-2.5), tobacco use (OR = 1.67; 95% CI = 1.07-2.6), and age (OR = 1.06; 95% CI = 1.03-1.08). These results suggest that employment as a law enforcement officer is associated with an increased cardiovascular disease morbidity and this relationship persists after considering several conventional risk factors.
It remains undetermined whether members of the law enforcement profession are at an increased risk for cardiovascular disease (CVD), compared with the general population. Several studies have suggested an elevated mortality due to CVD in this occupational cohort,1-5 while other researchers found CVD-related mortality to be similar to that in a reference group.6-8 Likewise, the prevalence of CVD risk factors, such as hypercholesterolemia, hypertension, or smoking, in law enforcement officers (LEOs) has been found to be either greater than9,10 or similar to11 that seen in the general population.
Evaluating either CVD mortality or selected risk factors may present a skewed view of the relationship between this occupational group and CVD incidence. Mortality from CVD is declining faster than CVD incidence in the general population,12 yet, in LEOs, very little research has included morbidity as an end point. The research available suggests that CVD morbidity in LEOs is similar to that in the non-law enforcement population,13 but to our knowledge, no other study has made this comparison. Less-conventional risk factors, such as chronic stress14,15 and rotating shiftwork,16 may be greater contributors to CVD in this group than in the general population. Moreover, these risk factors may be missed during a routine risk factor assessment because of their uniqueness.
In the law enforcement profession, it is uncertain if CVD morbidity is elevated relative to the general population and, if so, whether the occupation per se is a contributor to this incidence. Consequently, the present study addressed these issues by comparing the incidence of CVD and risk factors in a group of retired Iowa LEOs with that in a larger sample of the general Iowa population.
Retired law enforcement officers (LEOs) or their widows (n = 348) were identified from the benefits roster maintained by the Iowa Department of Public Safety. Officers are eligible for retirement after 22 years of state employment and after attaining 55 years of age. Since individuals may go on disability retirement at an earlier age, LEO <55 years of age were excluded from the analyses. Of the 258 respondents to the survey (74% response rate), 232 were subsequently used in the analyses.
The reference population consisted of participants in the 1996 Iowa Behavioral Risk Factor Surveillance System (IBRFSS) survey. Iowa is a participating state in the Behavioral Risk Factor Surveillance System supported by the Centers for Disease Control and Prevention. The IBRFSS, administered under the auspices of the Iowa Department of Public Health, is an ongoing monthly telephone survey designed to gather information on health risk behaviors of adult Iowans. In 1996, approximately 300 surveys were performed each month. Because all the LEOs in the present study were white males with a retirement pension, respondents to the IBRFSS were excluded if they were not while males ≥55 years of age with self-reported incomes of over $20,000. Of the 1478 male and 2122 female respondents to the IBRFSS in 1996, 817 met these criteria.
Retired LEOs, or their widows, were mailed a cover letter and the survey in January 1997. This questionnaire solicited information on cardiovascular disease-related hospitalizations, surgery (coronary artery bypass graft or angioplasty), and whether their physician had ever told them they had cardiovascular disease (myocardial infarction, stroke, or atheroma). The presence of the CVD risk factors of tobacco use, diabetes, hypercholesterolemia, and hypertension was determined. While not identical in format, these questions paralleled those used in the IBRFSS. Finally, they were asked if they felt that employment as a LEO influenced any of these conditions.
A three-week response time was given to the LEOs. Non-respondents were then contacted by telephone in an effort to obtain the questionnaire information. Subjects were considered to have provided informed consent by completing either the written or telephone survey. The Iowa Department of Public Safety and the Institutional Review Board of Iowa State University approved this study.
A CVD incident was defined as the officer's (1) having been informed by a physician that he had atheroma(s), or had experienced a stroke or myocardial infarction, (2) having undergone either coronary artery bypass graft surgery or cardiac catheterization, or 3) having been hospitalized for CVD since his retirement. CVD incidence and prevalence of risk factors were compared between the two groups by one-way analysis of variance. Multiple logistic regression analysis, which can control for several CVD risk factors simultaneously, was used to determine the relative influence of these risk factors on CVD. The dependent variable was CVD incidence, while age, diabetes, elevated body mass index (≥27.8 kg · m-2), hypercholesterolemia, hypertension, tobacco use, and occupation (LEO) were the independent variables. Maximum likelihood estimates of the logistic regression coefficients and 95% confidence intervals (95% CI) were determined using the Statistical Package for the Social Sciences (SPSS for Windows version 7.0; SPSS Inc., Chicago, IL). Data have been expressed as mean± SD. Statistical significance was considered to be P < 0.05.
The group of LEOs was retired a total of 2385 man-years or 10.2 ± 7.0 years per officer. The LEOs had a higher incidence (P < 0.001) of CVD than the general population (31.5 ± 46.5 vs 18.4± 38.7%). The LEOs were younger (65.5 ± 7.1 vs 69.0 ± 9.2 years; P < 0.001) and had a greater prevalence of diabetes, increased body mass index, and tobacco use (Table 1). Multiple logistic regression was used to determine if the greater CVD incidence in the LEOs could be attributed to either the profession or the risk factors. After controlling for the latter, law enforcement occupation was a significant (P < 0.0001) predictor for CVD in the combined group of LEOs and the general population. The odds ratio (OR) of CVD associated with this profession was 2.34 (95% CI = 1.5-3.6). With the exception of an elevated body mass index, the more conventional risk factors were also significant predictors of CVD in the combined group (Table 2).
The purpose of this study was to determine if LEOs experienced an elevated incidence of cardiovascular disease and whether this could be attributed to either the profession or the presence of common CVD risk factors. This study was felt to be worthwhile since CVD morbidity may be a more useful end point than CVD mortality and since the unique job characteristics of law enforcement may increase an officer's risk for CVD, exclusive of conventional risk factors. The results of this study suggest that employment as a LEO is associated with a higher incidence of CVD than that of the general population and that this occupation appears to be an independent contributor to CVD.
Besides the law enforcement occupation, several well-recognized risk factors also contributed to the CVD incidence seen in the combined group of LEOs and the general population cohort. These findings parallel those of a number of larger, prospective studies17-19 that indicate that age, diabetes, hypercholesterolemia, hypertension, and tobacco use contribute to CVD morbidity and mortality. Except for age, these risk factors are also major contributors to the excess mortality associated with several common chronic diseases.20 Nevertheless, after accounting for the influence of these conventional risk factors, the law enforcement occupation remained associated with an increased CVD morbidity.
In a 10-year prospective study, other investigators compared CVD mortality and morbidity between 220 policemen and 1428 non-policemen.13 At entry into the study, these policemen were 40.7 years of age and free of heart disease. Using logistic regression analyses, the OR for developing CVD that was associated with the law enforcement profession was 1.4. This ratio was not statistically significant because of a relatively low number of CVD events. In the present study, this OR was 2.34. Our cohort was 25 years older and had a higher CVD morbidity. While aging contributes to CVD risk,18,19 the influence of this factor was accounted for by multiple logistic regression analyses in both the present study and that of Sparrow and co-workers.13 Consequently, we feel that the differing findings may be due to our LEOs likely having been employed for a longer period of time.
It is unclear what aspects of the law enforcement occupation contribute to the increased CVD morbidity. This profession may indirectly increase CVD incidence by leading to increases in conventional risk factors, eg, elevated lipid levels, blood pressure, and body fat, in a time-dependent manner.9,10 This finding is reinforced here, since the group of LEOs had a higher prevalence of diabetes and an increased body mass index, compared with the general population. We accounted for these differences with the use of multiple logistic regression, yet this profession remained significantly associated with an increased CVD morbidity. Moreover, other research suggests that the interactive impact of these multiple risk factors on CVD risk is not significantly different between LEOs and a control group.11 Consequently, we feel that other aspects of the law enforcement profession are contributing to the increased CVD incidence seen here.
Of the 232 LEOs surveyed, 89 (38%) felt that their employment increased their risk for CVD. While many officers mentioned multiple factors, the most commonly cited were stress (81%), poor eating habits when working (24%), and rotating shiftwork (14%). Poor eating habits may be reflected in either an elevated body mass index, hypercholesterolemia, or diabetes. These factors were statistically accounted for in the present study and are readily detectable during a routine medical examination. However, the effects of chronic stress and shiftwork may be more difficult to determine. For example, the progression of atherosclerotic lesions appears to be associated with both an exaggerated cardiovascular reactivity to stress and high job demands.21 While the stressors of law enforcement vary considerably, as does its influence on individual officers, policemen have been found to have higher indicators of psychosocial stress than clerical workers, as well as elevated diastolic blood pressures and plasma norepinephrine levels.14,15 These responses were highest in the officers working a rotating shift.14,15
Shift work may16,22 or may not23,24 directly influence CVD risk. Working a rotating shift may indirectly increase CVD risk by affecting risk factors such as plasma lipid levels25,26 and obesity.26 However, after considering several common risk factors, other investigators found CVD risk to remain associated with increasing durations of shift work.22,27 Thus it is uncertain what aspects of the law enforcement profession directly contributed to an increased CVD incidence, although job-related stress and working rotating shifts may be involved.
In summary, this study suggests that employment as a LEO is associated with an increased risk of CVD. This relationship remains after considering the effects of age, diabetes, increased body mass index, hypercholesterolemia, hypertension, and tobacco use. Because these analyses were made on self-reported data and the study was retrospective in design, generalizations of these findings should be made with caution.
This work was supported in part by the State of Iowa's Department of Public Safety. The authors thank Patricia Busick, Michael Darie, Donald Shepherd and Mario Schootman of the Iowa Department of Public Health and Rosemary Carreon of the Iowa Department of Public Safety for assistance in the data-collection process.
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