Introduction

Currently, Diabetes Mellitus Type 2 (DMT2) affects 463 million people, projecting that for the year 2045, there will be 700 million people with this illness. Inhabitants of low and middle income are the most susceptible to develop the illness ¹. The etiology of DMT2 is of genetic and environmental type; among environmental factors obesity and non-healthy life styles are the one most frequently associated to the development of this illness ². Take care of DMT2 represents high economic and social costs both for the individuals, families and the health system itself, as consequence of the micro- and macro-vascular complications. During 2019 the expenses to treat the illness and its complications worldwide was 760,000 million dollars ¹.

The target of DMT2 treatment is to prevent or reduce the probability to develop complications, keeping glucose and lipids amounts within normal parameters, or as close as possible to them, by adhering to the typical treatment which consists in a balanced diet with calories control, increase of physical activity, consumption of medically prescribed drugs, and monitoring the own effects of the illness mainly in the lower limbs, sight, skin status, and kidney dysfunctions ³.

Self-management of DMT2 is understood as the group of activities that people with DMTW should perform in order to meet pharmacological and non-pharmacological therapeutic measures. A proper self-management of the illness is reflected in the glucose or metabolic control of the patient ⁴. Self-management is responsibility of the individual, thus, it is necessary that the ill person develops specialized skills under the guidance and monitoring of a multidisciplinary health team ³. Research evidence ^4-6 has reported that an affective self-management in people with DMT2 (diet, physical activity, self-monitoring) predicts a good metabolic control in individuals with good socio-economical level, highly educated and self-efficacy; this behavior is seen mainly in women. Recently, variables such as the work environment (working conditions) have been described as increasing the risk to develop the illness, such as working different shifts including night shift and long working hours, every day and/or weekly (>55 hr. per week) ^7-9. However, as far as it has been investigated, it is not clear if the variables of the working environment influence the self-management of those who already have the illness. With anticipation to the possible impact that this relationship will have, a scientific revision took place in order to explore the evidence available regarding the subject of working conditions and self-management of the DMT2. The results of this revision can be of great help for future health research or professional interventions in the first care level, that is, in the place where people perform their working activities.

Methodology

Exploratory systematic review to manage relevant literature in the area of interest ¹⁰ was performed through five phases, namely, identification of the research question, identification of relevant studies, selection of studies, data tracing and comparison, summary and presentation of results ¹¹.

Phase one, research question. What is known about the working conditions and self-management of DMT2? To answer this question the patient, exposure and outcome (PEO) methodology was used, in the following manner, a) P: people with confirmed diagnosis of DMT2; b) E: terms related to working conditions (working environment, employment, shifts, working hours, and occupational health); and c) O: self-management of the illness (self-care, physical activity, healthy diet, glucose self-monitoring, glucose and metabolic control). The databases used were PubMed, Scopus, Web of Science and Scielo Citation Index.

Phase two, relevant studies. The eligibility of criteria were quantitative and qualitative carried out in humans, expert opinions, reports of conferences and literature reviews. The results in all languages and all publication dates were included. The descriptors were DMT2, working conditions, and DMT2 Self-Management. Boolean operators OR and AND were used. Search criteria were Title/Summary.

The search strategy used for PubMed was; ("diabetes mellitus, type 2" OR "diabetes mellitus type 2" OR "glucose intolerance" OR "glucose intolerance" OR "hyperglycemia" OR "hyperglycemia") AND ("employment" OR "employment" OR "precarious work" OR "work environment" OR "work conditions" OR "shift work" OR "work schedule tolerance" OR "work schedule tolerance" OR "working hours" OR "occupational health" OR "occupational health" OR "occupational diseases" OR "occupational diseases") AND ("self-management" OR "self-management" OR "self care" OR "self care" OR "glycemic control" OR "metabolic control" OR "patient compliance" OR "patient compliance" OR "healthy diet" OR "healthy diet" OR "physical activity" OR "blood glucose self monitoring" OR "diabetes management"). The search yielded a total of 480 articles. The search period ranged from February 3 to March 20, 2020.

Phase three, selection of studies. The references located were imported to the Endnote web bibliographical administrator for the selection of studies. Duplicate references were eliminated (n= 216); a screening by title / title and summary (m=264) was performed according to the eligibility criteria in order to select only 24 studies.

Phase four, data tracing and comparison. Thirteen (13) complete text articles were recovered in order to evaluate the risk of bias and methodological quality using the tool Strengthening the reporting of observational studies in epidemiology (STROBE), list of verification which consists in 22 points to determine the quality of observational studies. Number 1 represents that the criterion was fulfilled, 0 means that the criterion is not clear and X represents absence of criterion ¹⁴. The final sample was comprised by six articles that were included in the review. Figure 1 shows the flow diagram of the declaration Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) for the process ¹².

Source: Own development

Figure 1 Process of selection of articles included in the review 

Phase five, summary and presentation of results. Data summaries and presentation of results in a narrative form, that is, in a qualitative manner, were prepared. The information obtained from the analysis was summarized under the following elements: (a) author, year of publication, place of study; (b) study design, objectives, population, sample size and methodology; (c) attributes and measurement of variables; and (d) results.

The ethical criteria that were met in this review were the one established in the ethics requirements for documentary research when copyrights are protected using the adequate cite for each analyzed article ¹³.

Results

The studies selected were performed in the United States and Japan (33% respectively) as well as in Brazil and Thailand with 16.7% each one: these were published between 2008 and 2019.

The evaluation that was obtained regarding the quality of the studies was average, 15.5 points. Articles 1 ²⁰ and 3 ¹⁶ were the ones with the best quality and ¹⁴ was the one with the best score. The aspects that showed the lowest score in methodology was the size of the study and in results it was other analysis, (Table 1).

The objectives of the studies were focused in evaluating the relationship between working conditions and health status of people with DMT2. Regarding the methodology, in 33.4% of the articles secondary data regarding clinical registers or national polls ^17,19) were assessed; and in 66.6% they corresponded to primary studies ^15,16,18,20. With respect to the study design, a 66.6% were sectional ^15,16,18,19, 16.7% cohort ¹⁷ and prospective ²⁰, respectively. The size of the sample varied ranged between 95 to 537 participants. The sampling was for convenience in 66.6% of the studies ^15-17,20, and 33.4% was at random sampling ^18,19. The total of the participants was 1840 workers whose age ranged from 20 60 65 years; the sex was reported only in 1,640 individuals, were 56% was male.

Working conditions described in the studies included shift and hours of work per week, psychosocial stress related to work, work load, control over work, social activities after work, non-scheduled work, self-report of the illness, satisfaction with work and type of occupation ^{(15, 20)}. For hours of work per week, ranges were established of: (a) ≤ 20 and (b) ≥ 40 hours ¹⁹ and (a) ≤35, (b) >35 and ˂60, y (c) ≥60 hours.²⁰ For the psychosocial stress related with work, four dimensions were included: (a) authority in decision making, (b) work demands, (c) peer support, and (d) supervisor support; to measure the psychosocial stress, four subscales of the Midlife Questionnaire designed to measure the psychosocial stress related with work in the United States ¹⁷ were used.

The factors work load, work control, social activities after work and non-scheduled work were identified from the content of the qualitative interviews applied to workers; from these subjects questionnaires were prepared to measure each factor. The self-report of the illness and the satisfaction with work was evaluated with questions prepared by the authors ¹⁶. For the type of occupation, the classification of occupations of the US National Health and Nutrition Examination Survey was taken, where 40 groups of the main occupation in the country ¹⁸⁾ are included.

For DMT2 self-management, terms such as metabolic control, glycemic control, health status, diet, exercise, and essential practices in people with DMT2 ^15,20 were used. The metabolic control was evaluated with blood pressure, anthropometric measures, lipid profile, glycosylated hemoglobin (HbA1c) and serum creatinine ¹⁵. For the glycemic control, indicators such as BMI, HbA1c and signs of retinopathy ^17,20 were used. The BMI was classified as obesity BMI ≥ 30 kg/m², overweight BMI ≥ 25 kg/m² and regular weight BMI ˂ 25 kg/m². The results of HbA1c were classified in suboptimal glycemic control HbA1c≥7% and good glycemic control HbA1c˂7%. To evaluate retinopathy signs, the clinical files of the participants ¹⁵ were reviewed. In other study only HbA1c was used, estimating the average of the lab results of four previous years, without using cohort points to classify them ¹⁶. Other authors evaluated them with a biochemical measurement with the following classification: normal HbA1c˂7%, suboptimal HbA1c≥7% and poor control HbA1c≥9% ¹⁹. For the result of serum creatinine no normal ranges used ¹⁵⁾ were specified.

For the health status, the records of fasting serum blood glucose, BMI and blood pressure of the previous six months registered in databases where the clinical records were included. The average of serum glucose was classified as a good glycemic control ≤ 130 mg/dl, the average of normal blood pressure ˂ 130/80 mmHg and the BMI normal ≤ 25 kg/m^{2 (18}. The diet, exercise and essential practices in people with DMT2 were measured with the Summary of Diabetes Self Care Activities Questionnaire with four items for diet and two items for exercise. The responses were evaluated using a frequency adherence scale for each activity of self-care in the last seven days, with a scale from 0 a 7 ¹⁶.

The studies that evaluated the work shift reported that a significant statistical relationship was found when working in the night shift with glycemic control and with the diet ^18,16.

Likewise, the research that included working hours per week showed that working >40 hours ¹⁹ and >60 hours ²⁰ was associated to a higher risk of suboptimal glycemic control.

In the research, the relationship between the labor environment and glycemic control was not clear. The studies that considered labor stress, the self-report of the illness and the satisfaction with work, only one showed a significant association between the self-report and the satisfaction with the diet ¹⁶, (Table 2).

Discussion

The purpose of this exploratory systematic review was to explore the evidence available regarding the subject of working conditions and self-management of DMT2. For this purpose, six studies published between 2008 and 2019 were studied; this evidences the scarce scientific literature that backups the variables considered in the study, DMT2 self-management and work conditions when the incidence and prevalence of the illness increases significantly ²¹ and the adults in economically productive age spend in their work places between 50 and 60% of the time awake, per day ²². This information suggests an urgent need to increase relevant research.

Main findings of this review show the absence of theoretical referential framework that sustain the variables and empirical indicators used to assess the factors that can influence on the health care of adults diagnosed with DMT2. The most used variables for working conditions were centered on the shifts ^15,16,18,20 and hours of work ^19,20. However, the International Labor Office acknowledged in 1984 the importance of identify, evaluate, and prevent psychosocial risk factors in the work place as a strategy for the prevention of the workers’ health ²³. Some authors ^16,17) of articles included in the review evaluated factors related to work, but used instruments that are not valid; nonetheless, currently for the measurement of these factors, the Copenhagen Psychosocial Questionnaire (COPSOQ) based on Karasek’s demand-control-social support model can be used, which has been translated into 25 languages, which allows carrying out comparisons of results at international level ²⁴.

Regarding DMT2 self-management, the most used variable was the glycemic control ^16,17,19, with measurement of serum glucose or HbA1c; in this respect the American Diabetes Association ³ mentions that DMT2 self-management is determined with the metabolic control through the following parameters: MBI between 18.5 and 25 kg/m², abdominal girth ˂94 cm for men and ˂90 cm for women, HbA1c ˂7%, evaluation of retinopathy, kidney function with glomerular filtration rate and presence of microalbuminuria ²⁵, blood pressure <130/80 mmHg ²⁶ and lipid profile with triglycerides ≤150 mg/dl and/or high density lipids >40 mg/dl in men and >50 mg/dl in women ³.

The differences in the definition and measurement of variables limit the comparison between studies, and, therefore, it is difficult to reach conclusions with respect to the influence of work condition in DMT2 self-management. The variables that showed a significant relationship with DMT2 self-management were work hours ^19,20 and shifts ^16,18) and occupation type ²⁰. The findings about working in the night shift are consistent with the information reported by Knutsson and Kempe ²⁷, who mention that the night shift is a risk factor to develop the illness. The same thing happens with long hours of work where Kivimäki et al ²⁸ identified that the higher amount of working hours, the higher the risk of developing complications due to the illness.

Methodologically, the formal process of the extensive search strategy was followed in various databases and the selection of studies that adhered to the described eligibility criteria. Thus, it is assured that this systematic exploratory review provides a coherent summary of the evidence available at the moment with respect to the working conditions and DMT2 self-management.

There is evidence of systematic reviews and meta-analysis that are focused in determining the relationship of working conditions with the risk of developing DMT2 ^27,28. However, this is the first review focused on the illness self-management. The results of this review confirm the need to perform more research in this respect taking care of the definition and the empirical indicators, both for working conditions and DMT2 self-management, with the purpose of searching a more thorough explanation for this health problem and, in the future, serve as basis to make interventions in the work place. This is an area of opportunity to influence the self-management of the illness due to the fact that the work place is where the person spends most part of the day.

Conclusions

With the exploratory systematic review it was possible to answer the question now being asked, that is, what is known about the working conditions and DMT2 self-management? The main finding was the absence of conceptual definitions and the difference between working definitions and empirical indicators used for each variable of study. The scarce information available to describe or explain the influence of the working conditions in the DMT2 self-management, along to the use of several indicators which make it difficult reaching a conclusion with respect to the relationship between these variables. Therefore, it is suggested to continue with research in this respect, since it is considered an area of opportunity that can explain the problem of illness self-management.

Conflicts of interests

The authors declare that there is no conflict of interest.

Financing

The authors declare that there was no funding of any kind.