Health-Related Quality of Life of Military Policemen in Salvador, Brazil: Cross-Sectional Study.

Background: Brazil is a violent society and police ocers play a fundamental role in this scenario. Police work is a stressful occupation. Dealing with routine violence, police ocers must have high standards of physical and mental health. Patrolling the streets involves several risks and stressful situations that may hamper military policemen's quality of life. This study aimed to identify factors associated with health-related quality of life in military policemen. Methods: A cross-sectional design study investigated a random sample of 329 male military police ocers, engaged in patrolling the streets of Salvador, Bahia, Brazil. A structured questionnaire was applied to the policemen during their working hours. Information was collected about age, education, marital status, housing, car ownership, police rank, working day, alcohol consumption, smoking, frequency of vigorous physical activity and weight and height, in order to calculate body mass index. Health-related quality of life was evaluated through the 36-Item Short Form Survey Questionnaire (SF-36). Work ability was assessed through the Work Ability Index questionnaire. Poor work ability was dened by a Work Ability Index 7-27 points. Multivariable linear regression models were used to measure the impact of police ocer characteristics on variation in the Physical Component and Mental Component Summary scores. Results: Normalised scores were below 50.0 for seven out of the eight SF-36 domains and for the two component summaries. The SF-36 Physical Component Summary was associated with poor work ability, while the Mental Component Summary was associated with poor work ability, excessive alcohol consumption, and younger age. Poor work ability affected 10.3% of the workforce. Decreases of 7.363 units (%) in the Physical Component Summary mean and of 12.862 units (%) in the Mental Component Summary mean were estimated for policemen with poor work ability. Conclusions: The military police ocers investigated presented poor health-related quality of life, associated with younger age, excessive alcohol consumption, and poor work ability, which may hamper the performance of their professional activities.

core-activity. This study is part of a larger study that evaluated other health aspects in military police o cers from Salvador [6].
Between February and April 2014, a trained researcher applied an individual, structured questionnaire to the policemen during their working hours. Information was collected about age, education, marital status, housing, car ownership, police rank, working day, alcohol consumption, smoking, frequency of vigorous physical activity and weight and height, in order to calculate body mass index. Obesity was de ned as body mass index ≥30.0 [7]. The policeman's own perception of their work ability was measured by the Work Ability Index -WAI [8]. The Work Ability Index questionnaire has been translated [9] and validated for the Brazilian population, with satisfactory construct validity and reliability [10] and test-retest reliability [11]. WAI has seven dimensions: current work ability compared to lifetime best (0-10 points), work ability in relation to demands of the job (2-20 points), number of diseases diagnosed by a physician (1-7 points), estimated work impairment due to diseases (1-6 points), sick leave over the past 12 months (1-5 points), own prognosis of work ability 2 years from now (1-7 points), and mental resources (1-4 points). The WAI index is calculated through the sum of points over the seven dimensions, varying from 7 to 49 points. The score can be classi ed according to four work ability categories: poor (7-27 points), moderate (28-36 points), good (37-43 points), and excellent (44-49 points) [12]. For the purposes of this study, poor work ability was codi ed as Yes (WAI 7-27 points) or No (WAI 28-49 points). Health-related quality of life was evaluated using the 36-Item Short Form Survey (SF-36) [13].
We selected a random sample, proportionally strati ed by the 27 battalions. As recommended by the SF-36 manual [14], we used Cohen's formula [15] to calculate a sample size capable of detecting differences of 5.0 points between the sample mean and the mean of a xed standard. To estimate the population's standard deviations, we adopted the values for males aged 25-34, 35-44, and 44-54 years old, as demonstrated in Table 10.3 of the SF-36 manual [14]. We used the value 30.24, related to the Role Physical domain, for men aged 44-54 years, since this was the largest of the three age groups and the eight SF-36 domains. The estimated minimal sample size was n=289, but this was deliberately in ated by 20%, resulting in a desired sample size of n=347 policemen. There were no refusals, however 18 individuals returned questionnaires with incomplete answers and were excluded from the study. The nal sample size was composed of 329 policemen.

Data processing and analysis
Based on answers to the SF-36 questionnaire, eight multi-item scales (physical functioning, role limitations due to physical problems, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems and mental health) were constructed and subsequently aggregated into two Component Summaries: the Physical Component Summary and the Mental Component Summary. The eight scales were scored using raw data (0 to 100 algorithms), while the respective normalized scores and the scores for the two summary measures was performed using QualityMetric Health The internal consistency of the SF-36 domains was evaluated using Cronbach's alpha. Values should exceed .70, but values ≥0.60 are acceptable in exploratory research [17].
Bivariate analyses used t-tests to compare means from the independent samples. Multivariable linear regression models were used to measure the impact of police o cer characteristics on variation in the Physical Component and Mental Component Summary scores. All prediction variables were inserted as a block in each equation, using the default selection method 'Enter'. Cases presenting studentized residual analysis varying around ± 3.000 standard deviations were identi ed as outliers. Data were analysed using SPSS version 20.0 (IBM Corp., Armonk, NY, USA).
All randomly selected policemen participated voluntarily in the survey. After explaining the objectives, participants signed a free informed consent form. All information related to the participants was con dential. The study was approved by the Ethics Committee in Research on Human Beings of the Medical School of Bahia for opinion number 554,724.

Results
Normalised scores were below 50.0 for the eight SF-36 domains and the two component summaries, except for vitality (51.8 ± 10.7). Scores for general health (44.6 ± 7.8) and social functioning (43.9 ± 11.1) were particularly low. The internal reliability indices for each domain, measured by Cronbach's alpha coe cient, varied from 0.624 (General Health) to 0.896 (Physical Functioning) ( Table 1). The policemen in the study were predominantly married (61.1%), presented low levels of education (64.4%), were soldiers (92.4%), owned a car (70.2%), and worked > 8 hours/day (79.6%). They did not practice vigorous physical activity frequently (47.7%), and some were obese (14.3%), smokers (5.8%), heavy drinkers (7.3%), and presented poor work ability (10.3%). Bivariate analyses revealed that the Physical Component Summary was strongly (P < 0.05 or less) associated with working day (P = 0.021), vigorous physical activity (P = 0.047), obesity (P = 0.043), and poor work ability (P < 0.001). The Mental Component Summary was strongly associated with excessive alcohol consumption (P = .002) and poor work ability (P < 0.001) ( Table 2).  The Physical (P < 0.001) and Mental (P < 0.001) Component Summaries of the health-related quality of life of the study population presented strong associations with poor work ability. The Work Ability Index is a complex construct that represents interaction between the individual's resources and their physical, mental and social work demands, the work environment, organizational culture and management. The WAI may be affected by various aspects of a worker's healthrelated quality of life [12]. Analogously, the SF-36 physical and mental component summaries are also complex constructs that involve a range of aspects related to work ability. Signi cant relationships were reported between WAI score and all SF-36 dimensions [19,20].
Compared to the other twelve variables in the models, poor work ability presented the best predictors of the physical and mental component summaries, by some distance. We estimated a decrease of 7.363 units (%) in the PCS mean and a decrease of 12.862 units (%) in the MCS mean among policemen with poor work ability. The great majority of these decreases re ect poorer physical and mental health-related quality of life for a policemen with poor work ability.
Minimal Clinically Important Difference (MCID) can be de ned as the smallest difference in score in the domain of interest which is perceived to be bene cial or harmful, and that would imply in a change in patient´s management. Ideally, the MCID should be ascertainded to each particular study population [21]. The MCID for group-level is necessarily smaller than for individual patient-level, because of greater measurement error inherent to patient's quality of life scores [22]. To the best of our knowledge, the MCID for the SF-36 Component Summaries (PCS and MCS) have not yet been determined for general or occupational populations, like military policemen.
It is unacceptable for 10.3% of these military policemen to present poor work ability. Policemen should be physically t in order to undertake patrols. The situation is even more worrisome when we consider that poor work ability is strongly associated with a lower mental health component in their health-related quality of life.
Policemen who were heavy drinkers presented MCS scores 5.354 lower than those who did not drink alcohol or were light drinkers. The inherently stressful work in the police service may be an important contributor to alcohol use. Excessive alcohol consumption is a frequent problem among a number of occupational groups in the USA, such as miners (17.5%) and construction workers (16.5%), aged between 18 and 64 [23]. In a large survey among male police o cers from California and New York City, 7.8% met criteria that indicated probable lifetime alcohol abuse or dependence [24]. This gure is similar to that found for the self-reported excessive alcohol consumption in our study: 7.3%.
Multiple regression analysis revealed a positive, statistically signi cant (b = 0.237; P = 0.011) association between age and the mental component of health-related quality of life (MCS). This association probably re ects a healthy worker survivor effect [25]. Stressful working conditions can affect policemen's mental health status over time, leading them to choose to leave the workforce, while those presenting optimal physical and mental health tend to remain in the job.
Some limitations of this study need to be addressed. Its cross-sectional design precludes the possibility of establishing causality among our key variables, mainly because of a lack of knowledge about their temporal sequence. Bi-directional cause-effect relationships between HRQoL component summaries (PCS and MCS) and poor work ability cannot be ruled out. Despite these limitations, this pioneering study was the rst to evaluate the HRQoL of military policemen in a representative sample from a large city in Brazil. The physical and mental components of HRQoL were strongly associated with poor work ability. The mental component of HRQoL was lower among heavy drinkers and those who were younger.
Given the key role military policemen play in community safety, these results are worrisome and deserve the attention of military police corporate managers in order to take preventive measures to protect these workers' health. Indeed, the results of this study provided valuable information to the military corporation health department to plan and establish its rst Medical Control Program [26].
In conclusion, military police o cers from Salvador city presented poor health-related quality of life, associated with excessive alcohol consumption and poor work ability, which may hamper their professional activities. The association between younger age and lower mental component of their health-related quality of life (MCS) is probably due to a healthy worker survivor effect. These ndings were important in planning the activities of a health care program for this particularly vulnerable occupational group.

Declarations
Ethical approval and consent to participate: The study was approved by the Ethics Committee in Research on Human Beings of the Medical School of Bahia for opinion number 554,724. All policemen participated voluntarily in the survey and signed a free informed consent form.
Consent for publication: Not applicable.
Availability of data and materials: The data supporting the ndings of this study are available from Liliane Lins-Kusterer but restrictions apply to the availabilityof these data, which were used under license for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of Liliane Lins-Kusterer.