Exercise capacity, Cardiovascular- and Metabolic Risk of German Police officers in an international comparison


 Background: The police force has a mandate to protect citizens and enforce law for public safety. Employment in the police force is recognized as a dangerous occupation and characterized by job-related physical hazards. Therefore, good health and adequate physical condition are necessary. The aim of this study was to determine cardiovascular, cardiorespiratory and metabolic risk parameters of German police officer (POs) in comparison to POs from other nations. Methods: 55 male police officers from Germany participated in the survey. Anthropometric measurements, cardiovascular and metabolic risk factors and blood parameters were taken. 10-year cardiovascular risk was calculated by using the Framingham Risk Score. The diagnosis of metabolic syndrome was based on the criteria of the International Diabetes Federation. Cardiorespiratory status was assessed by exercise spirometry. Results: The analyzed group of POs demonstrated a high prevalence of preobesity (BMI: 28.0±3.2, waist circumference: 97.8±12.4 cm). 61.8 % of POs showed an increased waist circumference. POs shows elevated cholesterol and triglyceride values and high prevalence of abnormal systolic and diastolic blood pressure. 10-year cardiovascular system risk of examined POs were 9.6 ± 7.4 %. The cardiovascular risk profile of our examined German cohort seems to be in the higher range in comparison to international data. 32 % of POs in our study group were diagnosed with metabolic syndrome. Maximal relative oxygen uptake of POs was 34.1 ± 8.0 ml/kg-1 ·min-1. Conclusions: To our knowledge this study was one of the first to assess data on cardiovascular health, metabolic syndrome and cardiorespiratory status of police officers in Germany. The results of our study population demonstrated the high cardiovascular and metabolic risk of German police officers and displaying a decreased cardiorespiratory fitness. The present study results demonstrated the need for implementation of interventions and creating health-promoting concepts like corporate sports activities and nutrition courses to counteract cardiovascular and metabolic risk factors and the subsequent development of cardiovascular and metabolic disease in this occupational group.


Background
The police force has a mandate to protect citizens and enforce law for public safety. But working as a police o cer (PO) is recognized as a dangerous occupation. The working condition include job-related hazards as the threat of bodily injury or death, intense physical stress and unpredictable emergency situations (1). Evidence indicates that the prevalence of traditional risk factors for cardiovascular disease among the police force is high (often higher than the general population) (2). This is demonstrated in high prevalence of typical cardiovascular risk factors, including metabolic syndrome, hypertension, hyperlipidemia, cigarette smoking and sedentary lifestyle (3). It is known that POs in the USA have a high risk of sudden cardiac arrest on duties (4). Reasons for this may be attributed to working conditions of job-related stress, inadequate sleep and unhealthy lifestyle (5).
Studies investigating German POs are limited, even though it is of major medical and socio-economic interest to improve on preventing work related development of disease. This study prospectively examined cardiovascular, cardiorespiratory and metabolic parameters in German POs in order to collect epidemiographic risk parameters associated with this occupational group. After conduction of the study a literature search was performed to compare our ndings in respect to international data. Our aim was to evaluate discrepancies in cardiovascular and metabolic risk amongst different countries.

Participants
Male police o cers from Germany, North Rhine-Westphalia, were invited to participate in this study via internet advertisements, social media and local corporate distribution after they responded to an o cial request. The recruitment of study participants was advertised at workplaces. Participation was voluntary. Inclusion criteria were working in police patrol service by shift work at the federal police force of Germany. A group of 55 male participants was included. The group consisted of male Caucasians with an age range between 18 and 55 years.
Examinations were performed at baseline and at one time at the Sports Medicine Centre in Hagen (Research Sector Prevention, Public Health and Sports Medicine, University Witten/Herdecke) by a trained clinician.

Assessment tools and procedures
A questionnaire was used to collect individual sedentary time at work (hrs), use of tobacco and alcohol, and to calculate the metabolic equivalents (METS) based on Ainsworth et al. (6). Values were assessed for one week. Dynamic sport activities such as jogging, cycling, swimming, soccer, martial arts, and anaerobic exercise are summarized under the term dynamic METS. One MET corresponds to 1 kcal·kg − 1 ·h − 1 .
The measurement of blood pressure was performed in a supine position with calibrated standard blood pressure cuffs. For the classi cation of blood pressure the ESH/ESC guidelines 2018 for management of hypertension were used (systolic blood pressure ≥ 140 mmHg Hypertension Grade I ≥ 160 mmHg Grade II and ≥ 1 80 mmHg Grade III) (7). Resting heart rate was measured by a 12-channel-ECG. Waist circumference was measured at the end of expiration in a standing position in the centre of the lower edge of the ribs and the upper edge of the iliac crest.
Participants were asked to fast (refrain from eating and drinking for 4 to 6 hours prior to the examination) before measuring body weight and having blood examinations in the morning. Body weight and body composition were determined using the Tanita BC-418MA segmental body composition analyser (8). For measuring body weight, body composition and body height, participants were instructed to wear only comfortable shorts with no other clothing or shoes. Blood serum parameters that were analysed included: Total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglyceride, glycated haemoglobin (HbA1c), C-reactive protein (CRP) and lipoprotein (a). Lipoprotein (a) was measured by our laboratory (Immun -Essay La Roche).
The Framingham score was used to calculate cardiovascular risk scores, based on observations and data from the Framingham Heart Study (9). Speci cally, in our investigations we applied the 10-year Cardiovascular Disease Risk Score Calculator based on the Framingham-Study (10). The following parameters were measured to calculate cardiovascular risk: age, diabetes, smoking, treated and untreated systolic blood pressure, total cholesterol, HDL levels and BMI.
The classi cation used to identify individuals with metabolic syndrome was based on the criteria of the International Diabetes Federation (IDF) in 2005 (11). The de nition focusses on four entities: obesity, dyslipidaemia, hypertension and insulin resistance. For diagnosis, obesity must be present, as well as two other criteria. The main criterion of the IDF de nition, central obesity, can be assessed by waist circumference or by BMI. The reference value of waist circumference was 94 cm.
Spiroergometry was performed in following manner (12)(13)(14): After successful gas and volume calibration a stress test was conducted beginning at 50 watts and continuously increasing by 25 watts every 2 min (ramp test). The test ended when the subject could no longer maintain the prede ned cadence of 80/min or if the subject was subjectively exhausted and there was no further increase in VO 2max after 20 sec. The spiroergometric analyses were conducted as previously described (13,14). The ventilator Aerobic threshold (AT) was de ned as the rst non-linear increase in the ventilatory equivalent for oxygen without simultaneous increase of the ventilatory equivalent for CO2. The respiratory compensation point (RCP) was de ned as the simultaneous non-linear increase of both ventilatory equivalents according to previously described recommendations (13,14).

Statistical Analysis
For statistical analysis, Stata / IC 13.1 for Windows was used. The anthropometric parameters, clinical characteristics, physical activity and cardiorespiratory tness parameters were described using the number of participants, means, standard deviations and medians. Categorical characteristics were displayed by specifying absolute and relative frequency. Comparison of the study data with other study results was completed by using means and standard deviations.

Study Population and Basic Characteristics
In this prospective study all 55 consecutively recruited male participants were included in the study. The participating POs were between 18 and 55 years old. The mean age was 45.3 ± 7.8 years ( Table 1). The POs had 25.2 ± 8.4 years of professional experience varying between 5 and 41 years. The corporate sports activity of all participants was 0.58 ± 0.93 hrs/week, the whole sports activity was 4.83 ± 4.29 hrs/week. Leisure time activity with vigorous physical activities was 2838 ± 2872 METs/week. Strength training, soccer, jogging, swimming, and cycling were considered vigorous physical activities. Cardiovascular risk factors were also taken into account for the diagnosis of metabolic syndrome according to the IDF (11). In the group of examined POs a distinct trend towards obesity became apparent. When considering lipid pro le percentages, elevated triglyceride was most frequently detected (43.6%). The major cardiovascular risk factors are shown in Table 3.  In Table 4, the 10-year risk for cardiovascular events and the heart/vascular age (years) shown are based on the Framingham Risk score.
The examined POs showed a mean 10-year cardiovascular system risk of 9.6 ± 7.4% and a mean heart/vascular age of 51.1. ± 13.9 years. They exceeded their actual mean age of 45.3 years by 5.8 years.

Cardiorespiratory Fitness
The relative oxygen uptake (rel. VO 2max ) was 34.1 ± 8.0 ml/kg -1 ·min -1 (Table 6). An absolute oxygen uptake (abs. VO 2max ) of 3.13 ± 0.62 l/min was shown. The maximum achieved wattage was 288.5 ± 48.6 W, while watt per kilogram was 3.14 ± 0.68 W/kg. Spiroergometry exercise parameters are displayed in Table 6. It is known that occupational sitting time is independently associated with the presence of overweight and obesity and other cardiovascular risk factors in men (17,18). The time of sedentary work activity was found to be related to an increased waist circumference, elevated serum triglyceride and serum CRP levels and lower HDL cholesterol levels and it can accelerate the emergence and progression of cardiovascular disease (18,19). Thomas et al. could provide evidence of a link between shift work and a higher level of cardiovascular risk. (20).
Workers on night duty generally show a signi cantly higher BMI as well as higher levels of cholesterol and triglyceride than workers on day shift (21). It is fair to assume that these factors also play an important role in the development of cardiovascular risk to the police o cers in our study.
In our group of POs the mean blood lipid levels, depicting cardiovascular risk, were increased above the upper  Table 7.
Regarding blood pressure values in the examined POs, a systolic hypertension was observed in 52.7%, and diastolic hypertension was observed in 49.1%, based on criteria for metabolic syndrome of the IDF.
The presence of hypertension is not only notable in our study cohort but can be observed in the entire population and other occupational groups (23,24). It seemed the prevalence of arterial hypertension in the group of German POs was higher compared to the general German population. Estimates show that slightly over 30% of the German population show arterial hypertensive blood pressure values (25). In international comparison, our study cohort shows values of systolic and diastolic blood pressure at the same levels as police o cers from the USA, India and Switzerland (22,26,27). Lower values are described in a Saudi Arabia police o cer cohort (28).
One of the most important cardiovascular risk factors is smoking. The prevalence of our examined cohort of nicotine consumption was 18.
2%. An international comparison shows that the smoking status of police o cers differs greatly. However, studies show that there is a link between shift work, speci cally working the night shift, and higher consumption of nicotine (21).
In this study we routinely analyzed lipoprotein (a) in our cohort. Lipoprotein In order to establish the 10-year risk for cardiovascular events, the "Farmingham risk score" was used. The 10year risk for cardiovascular events of our analyzed cohort was found to be at 9.6 ± 7.4%.
When dividing the Framingham risk score in categories of low, moderate, high and very high risk, our study population could be classi ed in the 'low risk' category, according to a 10-year chance on cardiovascular events being < 10% (33). A direct and valid comparison of the 10-year risk strati cation of cardiovascular events in POs in international studies could not be carried out due to the lack of comparative studies by using the same risk score. To date, there is only one study of American police o cers which found there to be a lower chance of cardiovascular events in 10 years' time (MW ± SD: 1.2 ± 0.5) (27). International studies con rm an increased risk for metabolic syndrome in POs (26,36,37). In our study the de nition of the International Diabetes Federation (IDF) was used for diagnosis of metabolic syndrome (16). The de nition of IDF is well-validated, posing adipositas as the central factor for de ning the metabolic syndrome. In comparison with other studies the de nition of IDF is more likely to be used in central Europe than de nitions of National Cholesterol Education Program (NCEP) and World Health Organization (WHO) (38,39). POs in our study cohort showed a mean waist circumference of 97.8 ± 12.4 cm. BMI was within the overweight range with a mean of 28.0 ± 3.2 kg/m2. Examined POs from Switzerland and India displayed lower mean abdominal circumferences and BMI values compared to our German cohort (22,34). Mean values of American POs concerning BMI are at the same range to our German POs, but American POs had lower mean values concerning the lipid pro le (Cholesterol, LDL and Triglyercide) (27,35). However, an increased abdominal circumferences and BMI do not appear to be exclusive to our investigated German cohort; they are globally detectable in police forces.
One reason of high abdominal circumferences in POs examined in our study seemed to be caused by sedentary work activities. But the impact of this fact is unkown. It is known that prolonged sedentary activities are associated with higher abdominal circumferences and the severity of the associated metabolic risk (40).
According to criteria of the IDF the metabolic syndrome was detected in 32.7% of probands in our study. Looking at various studies around the world the prevalence of metabolic syndrome in the general population varies from 23% France to 41% in USA (41). Compared to the regional prevalence of metabolic syndrome of the male population of North Rhine-Westphalia (Germany), the analyzed POs were found to be at an above-average risk of  Table 8 shows a comparison of the prevalence of metabolic syndrome in the professional category of "Police o cers" among countries.  (45), it was shown that there is a correlation between "perceived stress" (Perceived Stress Scale-10) on the job and a higher prevalence of the metabolic syndrome in Polish police o cers. Garbarino et al. (46) supports this result, proving that work-related stress induces the metabolic syndrome. The prevalence was found to be at 24.5% in the analyzed male police o cers. Furthermore, the irregular work hours, speci cally those at night, can trigger sleeping disorders (47,48). It is safe to assume that a high number of German police o cers also suffer from a sleeping disorder. A connection to the higher prevalence of metabolic syndrome is therefore quite possible. The study by McCanlies has shown that POs who claimed to sleep less than 6 hours per 24 hours had an increased prevalence for the metabolic syndrome by 150% in comparison to those POs who stated to sleep more than 6 hours per 24 hours (49).
It may seem surprising that German POs show a similarly high risk of metabolic syndrome to o ce workers (24,50). This could be due to the fact that both occupations conduct activities mostly while sitting. It is well known that sedentary activities carry a higher risk for metabolic syndrome (51) and cardiovascular disease (52).
Overall differences in individual status and private and professional activities exist and there will also be differences concerning the way of life between the countries. Therefore, in the future there is a need to perform prospective studies concern these factors.

Cardiorespiratory Fitness
High cardiorespiratory tness is an important factor in the prevention and treatment of cardiovascular risk, diseases and mortality (53,54). In detail, higher cardiorespiratory tness is associated with lower BMI, a lower risk for development type 2 diabetes and being active (55,56). Physical tness is an important basic requirement for police o cers on duty. As we know, there are only few researches about cardiorespiratory tness among police o cers. A direct comparison of the data investigated is challenging because of diverging parameters in age and BMI between the study groups. In our study the examined POs reached a mean oxygen uptake of (rel. VO 2max ) 34.1 ± 8.0 ml/kg -1 min -1 . When compared to police o cers of other countries, the rel.
VO 2max values of German POs are the lowest. But the comparison suffers from a lack of available study data.
Comparison to international literature German police o cers shows the lowest relative oxygen uptakes.
Canadian police o cers have the highest relative oxygen uptake (32.4 ± 5.4 ml/kg -1 min -1 ) (57) and police o cers from America and Finland also showed higher values (58,59). A comparative presentation of relative oxygen uptake is shown in

Conclusions
To our knowledge this study was one of the rst to assess data on cardiovascular health, metabolic syndrome and cardiorespiratory status of police o cers in Germany. The results of our study population demonstrated an increased cardiovascular risk of German police o cers and displaying a low cardiorespiratory tness. A high prevalence of elevated cardiovascular and metabolic risk factors is detected in our cohort, especially a high prevalence of increased diastolic and systolic blood pressure at rest and increased cholesterol and triglyceride values. A trend towards obesity could be seen in investigated individuals and general in the police force. An increased abdominal circumferences and BMI do not appear to be exclusive to our German POs cohort; they are globally detectable in the context of "police o cers". However, the cardiovascular risk pro le of our examined German cohort seems to be in the higher range in comparison to international data and the high prevalence of metabolic syndrome amongst POs was not exclusive to our German cohort but was identi ed globally.
A high cardiovascular tness is a de nite job requirement for law enforcement. The analyzed German POs have shown the worst cardiorespiratory tness of rel. VO2max when compared internationally. This shows both the urgency and necessity for establishing tness-related activities for the improvement of cardiovascular tness.
In conclusion, the present study results demonstrated the need for implementation of interventions and creating health promoting concepts like corporate sports activities and nutrition courses to counteract cardiovascular and metabolic risk factors to subsequent the development of cardiovascular and metabolic disease in this occupational group.