Association between Metabolic Syndrome and professional category: a cross-sectional study with Nursing professionals

Abstract Objective: to evaluate the association of Metabolic Syndrome and its components among Primary Health Care Nursing professionals in the state of Bahia, Brazil, according to professional category. Method: a cross-sectional, population-based and multicenter study conducted with 1,125 Nursing professionals. The independent variable was the professional category, dichotomized into technical and higher education levels. The outcome was Metabolic Syndrome following criteria from the National Cholesterol Education Program Adult Treatment Panel III based on anthropometric measurements and blood samples. The statistical analysis was performed by calculating the prevalence ratios and using Pearson’s Chi-square test. Results: the prevalence of Metabolic Syndrome was higher in the technical level category (PR=1.64; CI=1.29 - 2.06; p≤0.01). When compared to Nurses, these professionals were older, had lower incomes, worked more on duty and performed less physical activity on a regular basis. Among the Nurses, the most prevalent component was altered cholesterol (40.5%) and among the Nursing Technicians/Assistants, it was abdominal obesity (47.3%). Conclusion: the association between the Nursing category and Metabolic Syndrome was evident, with higher occurrence among technical level professionals.


Introduction
Metabolic Syndrome (MS) is a clinical condition that represent a relevant risk factor for the development of cardiovascular diseases, significantly contributing to the maintenance of the morbidity and mortality statistics in Brazil and in the world (1) . Recent studies show MS prevalence values from 8.9% to 44.0% in the Brazilian adult population, presenting an association with biological variables, lifestyle and work (2)(3) .
For being a syndrome, it consists of risk factors that reflect alteration of the homeostasis of different organic systems, whose indicators are used as criteria, namely: high blood pressure, reduction in the high-density cholesterol levels, increase in the serum glucose and triglyceride levels, and visceral fat accumulation (4) . It is an inflammatory organic state, characterized by insulin resistance and, consequently, it presents a complex triad, namely: atherosclerosis; pro-inflammatory cell catharsis [emphasis on Interleukin-1 (IL-1), Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α) and Ultrasensitive C-Reactive Protein (us-CRP)] and the MS components themselves (5) . Despite the cardiovascular risk already well established in the literature, these changes impose several deleterious health outcomes, such as neoplasms (6) and increased mortality due to any cause (7) .
It should be noted that MS reflects a consequence of lifestyle, whose main conditioning factor is work, as it determines the individuals' ways of being and living (8) .
In this aspect, no studies were identified in the literature with the purpose of investigating the prevalence of MS among Nursing professionals, taking into account the occupation variable. However, it becomes necessary to discuss the health status of these professionals, since they provide an essential service in all health institutions in the world (9) . In Brazil, the Nursing profession represents more than half of the collective of human health resources and has the peculiarity of being divided into categories that presuppose different training levels and, therefore, exposure to different occupational risk factors (10) .
Despite what was proposed for the Nursing work in the National Primary Care Policy (11) , in Primary Health Care (PHC), the profession presents characteristics of both specialized and craft work. It is based on the Taylorist-Fordist way of organizing work with an emphasis on doing, on the execution of routines and flowcharts (12) . The division of tasks is striking, legitimized by the instituted hierarchy and by care fragmentation. On the one hand, we have technical level professionals who do not have the autonomy to participate in the decision-making processes that will determine the dynamics of their work and, on the other, higher education professionals who perform managerial and care activities whose perspective is to obey the protocols established, eradicating the need for production from skilled work (13) .
In this sense, organization of the work in PHC exposes Nursing workers to a situation of increasing demands with an ever decreasing degree of autonomy.
These issues, associated with the current precariousness of work and employment, configure factors that can lead to psychological and physical illness in these workers, whose set of diseases includes MS (14)(15) .
Considering that the work performed by Nursing professionals in PHC can lead to the development of metabolic disorders, whose repercussions are echoed in the morbidity and mortality rates due to chronic noncommunicable diseases, this study assumes scientific relevance, as it recognizes the productive sphere as an important element in the social dimension of life, presupposing an ethical dimension in the scope of Workers' Health when acknowledging well-being at work as a right.
The study hypothesis assumes that the occurrence of MS differs across the Nursing categories, being higher among technical level professionals. Therefore, due to the importance of the theme in question and to the fact that no papers of this nature were identified at the national level, the objective of the current research was to evaluate the association of MS and its components among PHC Nursing professionals in the state of Bahia, Brazil, according to professional category.

Study design
This is a cross-sectional, population-based and multicenter study guided by the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) initiative (16) . Considering the territorial dimensions of the study scenario, the multicenter design allowed including individuals from the most diverse population contexts and, consequently, obtaining a broader overview of the outcome investigated, producing reliable findings to better translate the existing reality (17) .

Data collection locus
The study scenario was the state of Bahia (BA), Brazil, which, according to data from the Brazilian Institute of Geography and Statistics (18) , comprises 417 municipalities, organized into 7 mesoregions. For the purposes of equiprobabilistic calculation, these were stratified by clusters, whose unit was represented by the municipal unit. Through a simple random sample, 10% of the clusters of each stratum were drawn, making a www.eerp.usp.br/rlae

Period
The data were collected by visiting the Health Units in which the selected professionals, worked between 2017 and 2018. Prior training was offered to the interviewers to standardize the behaviors.

Population
The study population included a representative sample of PHC Nursing professionals whose number was 9,955 workers allocated to Primary Health Care Units in the reference year: 2016 (19) .

Selection criteria
All PHC Nursing professionals over the age of 18 years old, of both genders and in full exercise of their work activities, were considered eligible and were, even, willing to undergo the collection of blood material and anthropometric measurements. The exclusion criteria were as follows: working in PHC for less than 6 months, not providing direct care to patients, or being distanced from their usual activities due to medical leave or vacations.
Professionals who were pregnant, diagnosed with Burnout syndrome, depression or anxiety prior to admission to the service were also excluded, as well as patients with liver cirrhosis and those who were dependent on illicit drugs or alcohol (14,20) . All 1,195 Nursing professionals who worked in the PHC units of the 43 municipalities selected were considered eligible (14,20) .

Participants
Sample size calculation was based on a pilot study with a similar population. MS prevalence values were used for the exposed and non-exposed groups, of 20.0% and 33.3%, respectively. Considering an α error of 0.05, 90% power and a 1:1 ratio, and using the calculation formula for cross-sectional studies (21) , a sample of 464 professionals was obtained.
Due to the study design, the sample value was doubled, obtaining an n of 928, adding an additional 20% for possible losses and refusals, with a final sample of 1,114 Nursing professionals representing PHC in the state of Bahia, Brazil (14,20) .

Study variables
The exposure variable was measured using the research instrument in the block intended for the participant's identification data. In the field entitled "profession", the answer possibilities included the following: 1-Nurse, 2-Nursing Technician and 3-Nursing Assistant. For analysis purposes, the variable was dichotomized into "Nurse" and "Nursing Technician/ Assistant". It is noteworthy that the variable reflected the professionals' occupation in the health unit and not necessarily their training level.
The outcome variable was MS, dichotomized into yes/no, whose diagnostic confirmation adopted the criteria of the I Brazilian Guideline for the Diagnosis and Treatment of Metabolic Syndrome (22) and of the

National Cholesterol Education Program Adult Treatment
Panel III (23) . Individuals who presented at least three biology. The collection form was tested through a pilot study conducted with 30 Nursing professionals from a hospital.

Data collection
The initial approach to the professionals involved explaining the research objectives, risks and benefits, exclusion criteria considered and procedures to be adopted, such as anthropometric measurements and collection of blood material, after a 12-hour fast. In case the professionals met the criteria proposed and accepted to be part of the study population, signature of the Free and Informed Consent Form (FICF) was requested, thus guaranteeing formalization of their participation.
For the diagnosis of MS, the participants were directed to undergo the laboratory tests in a single laboratory, considered as a reference for each cluster, where blood samples were collected. Conventional enzymatic and colorimetric laboratory techniques were used to obtain the fasting blood glucose, HDL cholesterol and triglycerides serum levels (14,20) .
Abdominal obesity was verified by measuring waist circumference (WC), whose values reflect a reliable indicator of visceral adipose tissue (24) . WC was measured in a private office, safeguarding the professional's privacy, With the weight and height measurements, the Body Mass Index (BMI) was calculated according to the following formula: BMI=Weight(kg)/Height(m) 2 . The BMI values considered in the analysis were dichotomized into normal weight (BMI=18.5-24.99) and excess weight (BMI≥25.00) (22) . For this variable, 11 individuals who scored as low weight, that is to say, who presented BMI values≤18.49, were excluded.

Data treatment and analysis
The statistical analysis was carried out by descriptive analysis of the absolute and relative frequencies of the variables of interest, enabling prevalence estimates of the main dependent variable, as well as of its components.

Ethical aspects
The study was approved by the Committee of Ethics in

Results
The study population consisted of 1,125 Nursing professionals (94.1% response rate), most of whom were represented by the technical level category (59.6%).
It was noticed that, when compared to the Nurses, the technical level professionals were older; and that, despite having more stable contracts, they had lower incomes, worked more on duty and performed fewer physical activities on a regular basis. The occurrence of MS was higher among the Nursing Technicians/ Assistants for all the variables studied ( Table 1)     us understand the importance of these professionals for the consolidation of the SUS principles (28) .
However, the international literature has already firmly established the real context of the precariousness of work for Nursing professionals, who do not even have a wage floor or social recognition in Brazil (9) . It is believed that, as it is an eminently female profession, gender issues are negatively interfering with this issue, whose struggle has been dragging on for years, without any tangible or visible achievements. A research study on MS among workers conducted from a gender perspective concluded that its occurrence differs between men and women, presenting an inverse relationship between the income and schooling variables among women (29) .
In this sense, aspects related to work are capable of interfering with the workers' health, as they determine their way of life. A recent literature review that included research studies carried out in several countries and with various professional categories evidenced the association between MS and work-related variables, with emphasis on occupation (30) .
Occupation determines the level of remuneration, which in turn, is associated with MS. Limited resources drive the consumption of lower-cost food products, but with higher caloric contents, which favors the development of insulin resistance, hypertriglyceridemia and body weight gain. In addition to access to food, lower incomes can also interfere with the possibility of practicing physical and leisure activities, increasing the risk of MS (31) .
With a view to increasing income, it is not uncommon that Nursing professionals, especially mid-level (32) , be required to take on more than one work schedule, a finding corroborated in the current study. It is plausible to reflect on the following hypothesis: in PHC, the contractual regime for these professionals provides for 40 daytime weekly working hours, requiring night work as a form of second contract. Thus, a second employment contract determines lack of free time and, therefore, fewer physical smoking and an unbalanced diet (33) . In the current study, the use of illicit drugs was reported more than twice as often by the Nursing Technicians/Assistants than by the Nurses (data not shown in the tables).
Night work as a second contract significantly modifies life habits and is capable of inducing changes in the circadian cycle, whose implications include imbalances in body metabolism. In this aspect, the literature points out that the short sleep duration imposed by shift work increases the concentration of the ghrelin hormone and, consequently, a decrease in the leptin hormone, contributing to an increase in appetite and to weight gain (34) . Other evidence has shown that poor sleep quality can activate the hypothalamic-pituitary-adrenal axis, leading to increased secretion of cortisol and catecholamines, important factors in the pathophysiology of MS (35) . The role of reduced melatonin activity as a risk factor associated with the development of MS has also been investigated (36) .
In terms of eating habits, it allows less time to prepare healthier meals, resulting in the consumption of food products with high caloric content, in addition to irregular meal times. Eating overnight can be considered as metabolically unfavorable because the body has its glucose tolerance reduced, increased gastric emptying time, and altered body temperature (37) . In addition to that, Nursing professionals who work during the night usually do not engage in regular physical activities due to the fatigue associated with the nature of their work (38) .
In the PHC context, during the workday, Nurses spend more time seated attending the office or deliberating on administrative demands. Nursing Technicians/Assistants move more during the workday and perform activities with greater energy expenditure; however, in this study, it was noticed that the latter presented higher MS prevalence values. The role of physical activity as a factor that acts in the prevention of MS is already well established in the literature, as long as it is performed regularly and intentionally (39) .
The mechanisms by which physical activity prevents the occurrence of MS include the following: (i) increase in the number of mitochondria in muscle fibers through the production of peroxisome proliferators, improving the oxidative capacity of the muscles and reducing systemic inflammation; (ii) secretion of metabolically beneficial hormones, especially irisin; (iii) reversal of insulin resistance by the muscles promoting the use of serum glucose as a substrate; (iv) reduction in hepatic lipogenesis due to increased use of fatty acids by the muscles (40) . Regular physical exercise can promote browning of the adipocytes, making them metabolically active, which ultimately culminates in thermogenesis and increased energy expenditure (41) .
It was evident that the Nursing Technicians/Assistants were more overweight, with greater waist circumference and altered BMI. Central obesity, whose most easily measured clinical counterpart is waist circumference, has shown to be a strong predictor of MS, even regardless of BMI (24) .
Diverse scientific evidence suggests that one of the main factors that can accelerate the path to obesity is insulin resistance, which, to some extent, is genetically predetermined (42) . In addition to insulin resistance, visceral adipose tissue promotes the release of nonesterified free fatty acids which, in turn, accumulate in organs such as liver and muscles, further predisposing to insulin resistance and dyslipidemia. In addition to that, the adipocytes that make up visceral fat can produce several adipokines such as leptin, resistin, TNF-α, IL-6 and angiotensin II, which can, additionally, impact on insulin resistance and pro-thrombotic and pro-inflammatory states, in addition to other cardiovascular risk factors (41) .
With regard to age, although the Nursing Technicians/Assistants were older, the study evidenced being even higher in the technical level category. In this sense, it is assumed that these professionals seem to be more exposed to occupational exposure factors capable of culminating in the occurrence of MS. Evaluating the relationship between MS and the professional category can contribute to preventing its occurrence, representing a reduction in a significant number of cases, whose impact may be felt in the statistics of chronic non-communicable diseases.

Conclusion
In this study, the association between professional