The current labour market continues to be characterised by traditional demands on shift systems with night and weekend work. In certain sectors of the economy, shift work is essential to maintain production processes. In 2020, 13% of men in Germany worked night shifts and 15% worked rotating shifts (1).

Shift and night work are defined differently internationally, and studies often use the terms imprecisely (2, 3). The different use of the term in the primary studies of the meta-analysis by Ijaz et al. (4) prevents a comprehensive assessment of the effects of shift and night work on sleep, health or work-life balance. In Germany, night work is regulated by § 2 of the Working Hours Act (ArbZG) (5). It covers the period from 23:00 h to 06:00 h and applies to any work that extends more than 2 h into the night. In addition, in Germany the eight-hour day also applies to shift workers. The German Working Time Act (§ 7, § 15, para. 1) only allows a continuous 12-h shift system under certain conditions and with additional regulations.

Although there are concerns about such shift systems for reasons of productivity and performance, there is an interest in 12-h shifts from the perspective of both companies and shift workers themselves (6). Employers expect benefits for operational processes and employees expect more free time (7, 8). Overall, the data on the consequences of shift and night work is extensive but inconsistent, which is not least due to the lack of a standardised definition of shift and night work (3, 9) and the large number of different shift systems (10).

Obtaining enough high-quality sleep is essential for good health. However, night work leads to a physiological desynchronization of bodily functions (2, 9, 11–13). The change in sleep–wake rhythm not only causes additional burden but is also associated with a variety of impairments, most commonly sleep deficits and sleep disorders (8, 12–17). This leads to sleep-related mood disorders and a lack of recovery (e.g., daytime sleepiness, irritability, concentration problems) (14, 18), which increase the risk of errors and work-related accidents (14, 16, 18). It has been observed particularly in occupations with a high mental workload after more than 8 h of work (6, 18).

Numerous studies have associated night and rotating shift work with an increased risk of cardiovascular disease (9, 16, 19, 20) and metabolic diseases (9, 16, 20–22). The elevated risk of cardiovascular disease (15, 23) and type II diabetes (9, 15, 22, 23) has also been derived from meta-analyses and multi-cohort studies for long working hours. However, other reviews and studies have not provided convincing evidence of a link between shift work and cardiovascular disease (24–26) or type II diabetes (21). The longitudinal study (five-year follow-up) by Rossnagel et al. (27) also found no significant association between long working hours and cardiovascular disease or type II diabetes.

The contradictory data also applies to cardiovascular risk factors. While a number of studies (9, 11, 28–31) and the systematic review by Esquirol et al. (2) found an association between shift and night work and hypertension, longitudinal studies by Morikawa et al. (32) or Akbari et al. (28) or the cohort study by Hublin et al. (24) did not confirm this correlation.

Night work in particular has been associated with an increased risk of being overweight and obesity in several systematic reviews (33–35). In contrast, no such association was identified in the cohort study by Akbari et al. (28) or the meta-analysis by Saulle et al. (36). Other studies and the review by Esquirol et al. (2) have shown that shift and night workers have raised lipid levels (total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol, triglycerides) (31, 37) and glucose levels (fast blood sugar, fasting plasma glucose) (38), while in the studies by Morikawa et al. (32), Akbari et al. (28) or Dong et al. (30), indicators of lipid and glucose metabolism did not differ between shift and day workers.

It has also been observed that long working hours, shift and night work lead to changes in lifestyle and health behaviour (9, 12, 39). For example, it has been found that shift workers have unfavourable eating habits (22, 25), smoke more often (22, 25, 35) and are less physically active (22, 36, 40) compared to day workers. Other studies have found no evidence between shift work and physical inactivity (41, 42) or smoking (32).

Another well-known consequence of shift and night work is social desynchronization, which manifests in restrictions on family and social life (7, 25, 43, 44) and less participation in social activities. Night and weekend shifts, in particular, are at odds with the desire for evenings, weekends and holidays off (7). However, the results on the impact on work-life balance have also been found to be contradictory (7), with the duration and organisation of working time, as well as the opportunities for employee participation, moderating the result (10). Although long working hours appeared to make it more difficult to reconcile work and private life (45), a better work-life balance was confirmed for the 12-h shift system (46). Loudoun (47), on the other hand, found no difference in work-life balance for an eight-hour or 12-h shift system.

To summarise, there is a lack of meaningful longitudinal studies that address the influence of 12-h shift systems on indicators of sleep, cardiovascular health and work-life balance. In addition, the findings are inconsistent due to the heterogeneity of the methodology (e.g., definition of shift work, design, population, data collection, adjustment for potential covariates). Furthermore, the occupational group of machine and plant operators (MPO) is clearly underrepresented in the literature.

MPOs are primarily found in industrial production sectors (including the food industry). They are involved in the entire production process and must guarantee smooth production. Their range of tasks includes setting up, commissioning, operating and maintaining machines and production facilities, selecting and applying mechanical and manual production techniques, controlling the flow of materials and performing quality control and assurance tasks (48). In addition, there is coordination with upstream and downstream production levels and the documentation of production data.

For technological and economic reasons, MPOs requires a high proportion of night shift work, although two-shift operation is more common on weekdays in the food and beverage industry. Although a 12-h shift system increases the degree of utilisation of plant capacities, higher labour costs are incurred.

One of the primary stress factors for MPOs is the intense, sustained and concentrated attention required to capture, process and implement relevant process information. This can lead to changes in performance over the course of the day, with a particular drop in performance at night (49). Since the operating and control processes are mainly carried out while standing, a solid physical fitness is required. Good stress management is also essential, as maintenance and repair work often has to be carried out under time pressure (50).

The aim of the study was therefore to map the development of indicators of sleep, cardiovascular health and work-life balance after a period of 4 years (follow-up measurement T5) in MPOs working in a rotating 65-h shift system or exclusively during the day (8 h) in comparison to the baseline measurement (T1). It was hypothetically assumed that rotating 12-h shift work over a period of 4 years would have a negative impact on sleep, cardiovascular health and work-life balance under comparable baseline conditions for the two groups.

This study was a longitudinal study with a baseline measurement (T1) and follow-up after 4 years (T5). The data was collected annually from 2011 (first measurement point, T1) to 2016 (fifth measurement point, T5) at a company in the food industry in Saxony-Anhalt (>400 examinations). The 12-h shift system was introduced at this company in November 2009. Interim results (T2-T4) are not reported here since they do not provide any additional insights.

A total of 108 employees took part in the study, of whom 75 datasets from male MPOs were available which met the data quality requirements, i.e., 45 shift workers and 30 day workers (working regular daytime hours) took part in both the baseline and the follow-up measurement after 4 years; they form the data basis of this study. Since there were only four female MPOs in the baseline measurement, no women were included in the sample.

The examinations were carried out by THUMEDI Präventionsmanagement GmbH as part of the occupational health programme for shift workers. The examinations were carried out in the company’s medical centres, with each participant being examined for 30 min. All participants took part in the examinations voluntarily. Before the start of the examination, all employees received a letter with information on data protection, the conduct of the examination and data analysis. The anonymity of the data was guaranteed by means of a personal code.

The study investigated whether work in a rotating 12-h shift system compared to day work over a period of 4 years (T5) led to poorer sleep quality and quantity, whether the cardiovascular risk indicators increased, or whether the work-life balance changed. Firstly, the sample is described. After that, the results of the baseline measurement (T1) are shown for each of these constructs in a comparison of shift and day workers (t-test for independent samples, chi² test, contingency coefficient). Finally, the results of the repeat measurements (rANCOVAs) are presented for the respective constructs using the multivariate tests (Hotelling’s Trace).

The main and interaction effects between baseline and follow-up measurement (factor time) and the two groups (factor group), as well as the covariates are considered in the following.

As a result of the preliminary analysis, the covariates were included in the rANCOVAs as follows: age was included as a confounding variable for the sleep and cardiovascular health indicators (exception: for the PROCAM score). For the work-life balance the covariate children living in the household (children/household [number]) was included in the repeated measurement models. Since very high correlations (R ≥ 0.95) were confirmed for these covariates between T1 and T5, only the data from T1 were included in the analyses. The covariates chronotype, years in shift work (shift workers only) and regular sport/week were omitted as no practically significant correlations were found for these variables in the preliminary analysis for the sleep and health indicators.

From an occupational health perspective, shift workers should be productive, resilient and satisfied with their work for as long as possible. Based on previous research findings, the study hypothesised at the beginning that MPOs working 12-h shifts over a period of 4 years would experience negative effects on their sleep quality and quantity (72, 73), cardiovascular health (74) and work-life balance (7). MPOs who worked daytime jobs served as a comparison group.

However, shift workers differed from day workers at the baseline measurement in terms of significantly poorer sleep quality, shorter sleep duration, less favourable values for blood pressure, body mass index, HDL cholesterol, PROCAM score and greater dissatisfaction with the time available for social, cultural and sporting activities.

In fact, the cardiovascular health status had not changed significantly in either group at the follow-up. For shift workers, the quality and quantity of sleep only decreased significantly after the night shift over a period of 4 years. Nevertheless, most shift workers (T5: 89%) were satisfied with the time they had available for sleep. For day workers, the comparatively higher sleep quality and longer sleep duration from the baseline measurement were also confirmed in the follow-up measurement. The effect on satisfaction was unexpected. Shift workers were significantly more satisfied with their available free time in the follow-up. This satisfaction was now even higher than that of day workers, for whom satisfaction was comparable at both times (T1, T5). In addition, both groups reported significantly fewer impairments after 4 years, whereby this effect was moderated by the number of children to be cared for in the household. Age did not have a significant effect on sleep quality and quantity at any measurement time or in any group. However, with the exception of the lipid metabolism indicators, the known age effects were confirmed for the cardiovascular health indicators (BP, BMI, HbA1c, PROCAM score).

Shift workers slept on average 72 min less than day workers at baseline, whereby their average sleep duration after the night shift was still 30 min shorter than during the morning shift. For the follow-up, shift workers slept an average of only 5 h 18 min after the night shift, i.e., definitely too little. Daytime sleep after a night shift is also considered less restorative as it is more prone to disruption and rarely reaches the depth of night-time sleep (8, 43). According to Hulsegge et al. (17), around a third (35%) of shift workers and a quarter (27%) of day workers sleep less than seven hours. A representative survey of working people in Germany (n = 4,511, 31–60 years) also found that 12% of shift workers can be assumed to have insufficient rest (75). Research has shown that a lack of rest can lead to sleep disorders in the long term (75). Health experts therefore recommend that shift workers who sleep less than 7 h a day should take a power nap in between (13).

Although the additional days off outside the 12-h shifts offer employees opportunities to compensate for sleep deficits and lack of rest, they are probably not enough to fully compensate for them. In the study by Cunha et al. (8), only just under half (49%) of shift workers could imagine working in a 12-h shift system until retirement age. In addition, shift work appears to lead to a decrease in sleep quality after a short period of time (73).

Sleep disorders are also widespread in the general population. In Germany, 29% of all men (18–80 years) (57), and in an Austrian study 27% of all men (16- ≥ 70 years) have reported poor sleep quality (PSQI score >5 pts) (76). Chronic sleep disorders (PSQI score >10 pts) were not reported by Zeitlhofer et al. (76) and by Hinz et al. (57) for 5% of men.

In the study by Hinz et al. (57), the mean PSQI score for men in the general German population (18–59 years) was 4.3 pts In contrast to our sample, there was an age effect, according to which the PSQI score increased slightly with increasing age (<40 years: M = 3.9 pts, 50–59 years: M = 4.5 pts). In the study by Zeitlhofer et al. (76), the PSQI score also increased with increasing age in men from 2.5 (19–24 years) to 5.5 pts (55–59 years). Compared to these two studies, the day workers in the present study showed significantly better sleep quality with an average of 3.5 pts at baseline and 3.1 pts at follow-up. In contrast, shift workers reported slightly worse PSQI scores at the follow-up (T5: M = 4.8–5.1 pts) than in the general German population (57).

The correlations to the PSQI score between baseline and follow-up (SW: R = 0.49, DW: R = 0.60) and between morning and night shift (T1: R = 0.63, T5: R = 0.72) correspond to a variance explanation of 24–52%. Accordingly, only those who reported good sleep quality at baseline tended to also report this at follow-up. This also applies to the correlation between morning and night shift. Obviously, sleep behaviour is based on ‘third variables’ that occur independently of working hours. Sleep is a multidimensional construct and the causes of sleep problems are manifold.

With regard to cardiovascular health, the 12-h shift system had hardly any effect over a period of 4 years in this study. On the contrary, significant age effects were found. It is assumed that shift workers develop strategies to maintain their health and well-being that prepare the body for 12-h shifts or compensate for the effects of working past 12 h (8). To categorise the health status of shift and day workers, comparative studies that represent the general German male population and approximately the age range of the study have been used; they are as follows: German Health Interview and Examination Survey for Adults (DEGS1 study, 18–59 or 18-64 years) (77–80), PROCAM study (n = 5,389 men, average age: 47 years) (66) and Diabetes Cardiovascular Risk-Evaluation: Targets and Essential Data for Commitment of Treatment (DETECT study, n = 3,672 men, 40–65 years, average age: 53 years) (81).

From a preventive point of view, there is a need for action not only for shift workers but also for day workers with regard to cardiovascular risk. For example, almost two thirds (62%) of shift workers and 40% of day workers were considered to be hypertensive at the time of the follow-up, of whom only 43 and 13%, respectively, were taking antihypertensive drugs. The decrease in average blood pressure observed over the four-year period among shift workers is probably a medication effect. In future, occupational health programmes need to focus on increasing the proportion of people with hypertension treated with medication, regardless of whether they work only during the day or in shifts.

Furthermore, about half of the shift workers (47%) and day workers (57%) were found to be overweight and 33 and 10%, respectively, were obese. In addition, lipid metabolism disorders were present in both groups. Although the risk of a heart attack in the next 10 years could be classified as low for the majority of MPOs (T1:T5: <10%: 84 vs. 82%, DW: 90%), it had increased in both groups for the follow-up (M = 6.3 vs. 5.1 pts) although this was not practically significant. After 4 years, 4% of MPOs had a high PROCAM risk (T1: 1%).

In the study by Ohlander et al. (82), day workers had a lower prevalence of high blood pressure (8%) than shift workers (without night shift: 12%, night shift workers: 11%, rotating shift workers with nights: 10%). However, these prevalences are significantly lower than in our study and also lower than in the DEGS1 study, in which 15% of men had hypertension (77). The low prevalences are explained by the healthy worker effect and higher medical monitoring of employees compared to the general German population (82). Rashnuodi et al. (31), on the other hand, found elevated blood pressure in 44% of shift workers and 28% of day workers. Esquirol et al. (2) and Boini et al. (35) also postulate an increased risk of hypertension for shift workers, although the duration of exposure could influence this correlation. According to Su et al. (83), 12-h night work leads to an increase in blood pressure and heart rate as well as delayed blood pressure recovery. No association between shift work and high blood pressure was found in the longitudinal studies by Morikawa et al. (32), Hublin et al. (24) or Akbari et al. (28).

The average body mass index in this study is comparable to the mean values of Ohlander et al. (82) for both shift and day workers (SW with night work: M = 28 kg/m², DW: M = 26 kg/m²). But the proportion of obese people among shift workers is significantly lower here (22–24%) than among our shift workers (33%), but slightly higher for day workers (12% vs. 10%). In contrast, only 20% of men in the DEGS1 study were affected by obesity (78). Results from reviews (34, 35, 84) and the longitudinal study by van Drongelen et al. (33) have confirmed that night work in particular is associated with an increased risk of being overweight and obesity. However, when the results were adjusted for potential confounders (e.g., age, physical activity), the evidence was insufficient (33). In the cohort studies by Dochi et al. (37) and Akbari et al. (28), the mean values for the body mass index were in the normal range (<25 kg/m²) and did not differ between shift and day workers. This result was also reported by Rashnuodi et al. (31), whereby the mean values of the body mass index (28 kg/m²) were in the overweight range. Consistent with these results, the prevalence of being overweight, but above all obesity, also increased with age among the men in the DEGS1 study (78).

In this study, the average increase in blood lipids occurred equally in both groups and could not be attributed to shift work, but rather to an age effect. There is consensus here with the results of Morikawa et al. (32), Dochi et al. (37), Akbari et al. (28) and Dong et al. (30), who also found no differences in lipid metabolism indicators between shift workers with night work and day work. In contrast, lipid metabolism disorders have been frequently found in reviews for shift and night workers (2, 28, 31, 37). Compared to the DEGS1 study (TC: M = 5.0 mmol/l, HDL-C: M = 1.3 mmol/l), the MPOs showed slightly higher mean values for total cholesterol (T1:T5: M = 5.3 vs. 5.5 mmol/l), for HDL cholesterol the mean values were comparable to those of the DEGS1 study (1.3 mmol/l) (80) and the PROCAM study (1.2 mmol/l) (66). Overall, 51% of those analysed in the DEGS1 study had borderline elevated levels of total cholesterol, 16% had high levels of total cholesterol and 21% had low levels of HDL cholesterol (80). In contrast, the sample shown here indicates a less favourable lipid metabolism status (T5: 31% elevated and 33% high TC values, 23% low HDL-C values). Boini et al. (35) found low HDL cholesterol in permanent night and rotating night shift workers, while Guo et al. (15) found no association between shift work and low HDL cholesterol. However, the link between lipid metabolism disorders and night shift work has not yet been clearly established (2, 25).

In terms of glucose metabolism, shift and day workers did not differ longitudinally; 12-h shift work did not have a negative effect on the HbA1c value over 4 years. On the contrary, the HbA1c value also increased with increasing age (T1-T5: R = 0.45–0.32). This finding contradicts the studies in which a higher prevalence of diabetes is postulated for shift and night workers compared to day workers (2, 38, 85). In contrast, results from the studies by Morikawa et al. (32), Akbari et al. (28) or Dong et al. (30), in which no differences were found between shift and day workers with regard to glucose metabolism, are consistent with the results given here. Unexpected was the decrease in the average HbA1c value for follow-up measurement in both groups. One possible explanation for this could be that the dietary habits of those affected had changed as a result of occupational health counselling.

Nevertheless, it is worth noting that 31% of shift workers and 23% of day workers had HbA1c values in the prediabetic range for the follow-up and 7% of all MPOs were affected by manifest diabetes. The prevalence of diabetes was therefore higher than in a comparable study with 12-h day and night shifts (85). Here, 5% of alternating shift workers (n = 4,150, average age: 45 years) and 3% of day workers (n = 5,976, average age: 44 years) reported diagnosed diabetes mellitus. After additional adjustment of the diabetes risk factor (Find-Risk-Score), the prevalence of diabetes was on average 23% higher for shift workers compared to day workers. However, this effect was not significant and was primarily attributed to the more pronounced Find-Risk risk profile of shift workers (85). The DEGS1 study found a diabetes prevalence of 3% for men (79). In both studies, the prevalence increased with increasing age (79, 85).

The PROCAM score used to summarise the assessment of cardiovascular health. The calculated risk of a cardiovascular event in the next 10 years differed significantly between the groups (η²_p = 0.08—medium effect) and increased with age. The age effect is also consistent with the findings from comparative studies (15, 66, 79). The average PROCAM score for the follow-up was 6.3% for shift workers and 5.1% for day workers, which is still in the low-moderate range (66). In the PROCAM study, an average PROCAM risk of 6.8% was determined (66). In comparison, a significantly higher mean value of 9.2% was determined for the PROCAM score in the DETECT study (81).

Our findings are consistent with those of the meta-analysis by Vyas et al. (19), according to which shift workers have a higher risk of cardiovascular disease than day workers. However, the moderate increase in PROCAM risk for the follow-up is interpreted more as an age effect and less as a shift system effect, i.e., the fully continuous 12-h shift system does not appear to have an effect on cardiovascular risk. In the longitudinal study by Guo et al. (15), no clear tendencies for an increased cardiovascular risk among shift workers were recognisable for men over a period of 22 years. Yong et al. (26) also found no evidence of an increased cardiovascular risk among 12-h shift workers in industrial production.

From a medical point of view, it is worrying that a significant proportion of the cardiovascular risks in the MPOs were only diagnosed as a result of the study. Most of them were unaware of their risk factors or diseases. As a result, they were not receiving medical treatment. This is where the potential lies for holistic occupational health care in Germany, which takes into account not only the working conditions but also the individual interactions between work and physical and mental health, which can jeopardise employability.

The predictability and plannability of working hours are the key to work-life balance. The 12-h shift system means that shift workers are exposed to work-related stress for longer, but have more continuous time for relaxation, family and non-work activities (8). In addition, there is the financial advantage of shift allowances, less travelling time and costs, and free time at unusual times of the day (8).

Satisfaction with the time available for social and leisure activities changed significantly differently in the groups between the two survey dates. While the shift workers were more dissatisfied at the baseline measurement, a positive satisfaction effect was registered over the four-year period. In addition, private life was hardly affected by shift work. Accordingly, the decision in favour of a 12-h shift schedule can be useful for shift workers at certain stages of life (e.g., with young children), while health aspects are of secondary importance in this context (8). On the other hand, shift workers felt the sleep-related effects and occupational wear and tear of a shift system with night work. Irrespective of this, the benefits of the additional days off of a 12-h shift system described by Berkam et al. (86) appear to contribute significantly to the satisfaction of shift workers. Overall, the findings point to a very diverse family and social private life for shift workers.

The family and social conditions of the shift and day workers were comparable at both measurement times: just under 80% of MPOs lived in a partnership. Around half of them were childless and only 8 and 10% of the shift workers had children up to the age of three in their household, so that hardly any adverse effects were expected.

In essence, the development of cardiovascular health over the course of a lifetime must be assumed to be multi-causal. The underlying mechanisms for the health consequences of shift work are not yet fully understood (2, 87). So far, no causal relationship between shift work, disturbed sleep and health risks has been proven (16, 25), even if numerous studies suggest this relationship. It is evident that general resilience decreases and illnesses increase with age.

The influence of shift work on cardiovascular and metabolic diseases is most frequently explained by desynchronized circadian rhythms, sleep disturbances, unhealthy diet, psychosocial work stress and social inequality (2, 25). Although the body can adapt to changes in the daily routine in the short term, recurring disruptions to natural biological rhythms such as night work can lead to sleep disturbances and have health implications (including weight gain, increased lipids, coronary heart disease, type II diabetes) (16, 19). The consumption of energy-dense foods during the night shift also appears to favour the development of dyslipidaemia and insulin resistance (88). Lifestyle changes include unhealthier eating habits (22, 25), smoking (22, 35), reduced social (43, 44) or physical activity (22, 36, 40) have been discussed as further possible causes for the development of cardiovascular and metabolic diseases. In this study, more than half (57%) of the shift workers were regularly active in sports (DW: 80%) and one third (33%) were smokers (DW: 30%). In previous research, only a few studies have focused on measures to improve the health problems of shift workers. The current review by Wasiewicz-Ciach et al. (13) summarises measures that shift workers can take to better protect their health.

In summary, the study showed that a 12-h rotating shift system is associated with poorer sleep quality and shorter sleep duration compared to working 8 h during the day. Although these effects worsened over the four-year observation period, this only occurred after night shifts. This means that the hypothetical negative impact of a 12-h shift system on sleep can only be partially confirmed. During the same period, shift workers’ satisfaction with the 12-h shift system increased, reaching a level comparable to that of day workers. In addition, both groups reported a decrease in work-related impairments. These results lead to the rejection of the hypotheses regarding the negative impact of a 12-h shift system on work-life balance. In contrast, the cardiovascular health of the MPOs in both groups did not change over the observation period. This hypothesis must therefore also be rejected.

The consequences of shift work are complex and depend on the specifics of the shift models. For acceptance among employees, it is crucial that shift work and non-work needs can be satisfactorily reconciled. In this respect, 12-h rotating shift systems seem to offer advantages over regular eight-hour day work. However, the shorter sleep duration and reduced sleep quality after night work are additional limitations that endanger the long-term employability of shift workers, especially older workers. To counteract this, workers must be offered sufficiently long rest periods after night work to compensate for sleep deficits.

There is no ideal shift model that can eliminate all the unfavourable effects of night work on employees. Night work is always accompanied by a desynchronization of the circadian and social rhythms. It is therefore necessary to find solutions that promote the health of shift workers. The 12-h shift system and the associated distribution of days off and work days affect the quality and quantity of sleep.

Since sleep disorders can reduce performance and quality of life and lead to long-term health problems, they must be detected and treated at an early stage. In this context, occupational medicine can provide a valuable supplement to care provided by general practitioners and specialists. Its task is to limit adverse effects of night shift work on sleep, health and work-life balance. Individual measures for better sleep hygiene could be just as beneficial as an effective company health management system with a focus on sleep and cardiovascular health in achieving a successful outcome in prevention.

The findings on cardiovascular health indicate a need for prevention and medical care for both shift and day workers. Monitoring the prevalence of hypertension, overweight and obesity would be relevant to health, but should be placed in the context of a healthy lifestyle.