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Occupational Medicine Advance Access originally published online on April 2, 2007
Occupational Medicine 2007 57(5):337-341; doi:10.1093/occmed/kqm021
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© The Author 2007. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Reduction of oxidative stress by compression stockings in standing workers

Roberto Flore1,2, Laura Gerardino1,2, Angelo Santoliquido1,2, Cesare Catananti3, Paolo Pola1,2 and Paolo Tondi1,2

1 Department of Medicine, A. Gemelli University Hospital, Catholic University of the Sacred Heart, Rome, Italy
2 Division of Vascular Medicine, A. Gemelli University Hospital, Catholic University of the Sacred Heart, Rome, Italy
3 A. Gemelli University Hospital, Catholic University of the Sacred Heart, Rome, Italy

Correspondence to: Roberto Flore, Department of Medicine, Catholic University of the Sacred Heart, A. Gemelli University Hospital, Largo A. Gemelli, 8-00168 Rome, Italy. Tel: +39 06 30154294; fax: +39 06 35500486; e-mail: flore.roberto{at}libero.it


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background Healthy workers who stand for prolonged periods show enhanced production of reactive oxygen species (ROS) in their systemic circulation. Oxidative stress is thought to be a risk factor for chronic venous insufficiency and other systemic diseases.

Aim To evaluate the effectiveness of compression stockings in the prevention of oxidative stress at work.

Methods ROS and venous pressure of the lower limbs were measured in 55 theatre nurses who stood in the operating theatre for >6 h, 23 industrial ironers who stood for up to 5 h during their shift and 65 outpatient department nurses and 35 laundry workers who acted as controls. Subjects and controls were examined on two consecutive days before and after work and with and without compression stockings.

Results Without compression stockings, lower limb venous pressure increased significantly after work in all subjects and controls (P < 0.001), while only operating theatre nurses showed significantly higher mean levels of ROS (P < 0.001). There was no significant difference in venous pressures and ROS levels after work in subjects or controls when wearing compression stockings.

Conclusions Our data suggest a preventive role of compression stockings against oxidative stress in healthy workers with a standing occupation.

Keywords      Compression stockings; oxidative stress; standing occupations


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Chronic venous insufficiency (CVI) of the lower limbs is common in developed countries worldwide and results in considerable morbidity. Established risk factors for CVI include older age, female gender, geographic factors, pregnancy, family history of venous disease, obesity and occupations associated with orthostasis. In particular, an association between CVI and prolonged standing has been reported [1–5].

Venous hypertension of the lower limbs is the main mechanism involved in the onset and progression of CVI and leads to an inflammatory process in the microcirculation [6]. Several mediators of vessel wall damage are activated, including reactive oxygen species (ROS) which induce chemotaxis as well as leucocyte and platelet activation. Oxidative damage of the endothelial membrane and increased vascular permeability is followed by skin changes and oedema. As these mechanisms work together, cell damage and venous stasis increases [7, 8]. ROS are also involved in atherogenesis, thus increasing cardiovascular risk [9, 10], and oxidative stress has also been associated with other systemic diseases, including cancer and degenerative disorders [11].

Previous studies by our group have shown a local overproduction of ROS in the lower limbs of patients affected by varices of the long saphenous vein after 1 h of standing and that this can be corrected by stripping of the long saphenous vein [12, 13]. In a recent study, we observed that operating theatre nurses, without any sign of CVI, who stand for >90% of their working time, show high levels of venous pressure of the lower limbs and overproduction of ROS after work [14].

Until now the most commonly recommended preventive measure against CVI has been the use of graduated compression stockings (GCS). Light compression stockings increase venous blood flow in the supine position and prevent leg swelling after prolonged sitting and standing. Recent observations show that a significant increase in circumference and volume of the legs may be observed in women not wearing stockings which disappears when elastic compression stockings are worn during the day. Moreover, GCS are widely used as prophylaxis against deep venous thrombosis in surgical patients [15–17].

The aim of the present study was to evaluate the effectiveness of the use of compression stockings in the prevention of oxidative stress during work requiring prolonged standing.


   Methods
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 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
Subjects were operating theatre nurses working at the Gemelli University Hospital in Rome and ironers working at an industrial laundry. Controls were outpatient department nurses at the same hospital and workers employed in the department store of the same laundry. Working time ranged from 7 a.m. to 2 p.m. All subjects filled out a questionnaire concerning the time spent standing at work, personal data, habits, family risk for venous diseases, pregnancies, clinical history and current medication. All selected subjects underwent clinical examination and an EchocolorDoppler of the lower limbs (Acuson X/P128, USA) in order to assess the presence of CVI or deep venous reflux.

The number of hours reported as standing were checked by the investigators.

The operating theatre and outpatients department temperatures ranged between 20 and 24°C (relative humidity 40–50%). The industrial laundry was air conditioned with temperature and relative humidity similar to the above-mentioned values (ranging between 21 and 25°C and 40 and 55%, respectively), even though ironers were periodically exposed to higher temperature and humidity.

Subjects gave their written informed consent and the study was approved by the Catholic University Ethics Committee.

Both study groups and controls were examined for two consecutive days. On the first day they did not wear any compression stockings. The day after they wore compression stockings (Sigvaris collant KKL class I, ankle pressure: 18–21 mmHg at the ankle) during working time. The stockings used were categorized as mild strength (Grade I) according to the classification of the European Commission of Normalization [18].

Subjects were examined in a stable temperature room (20°C) before and after their working time. In all subjects, the following procedures were also performed:

  • Venous pressure measurement of the lower limbs: while the subject standing we set a sphygmomanometer tourniquet at the calf and measured the pressure at the long saphenous vein root with a Doppler 8 mHz probe in each limb according to a standardized previously described method [19]. The value obtained was the mean between the result at left and right leg.
  • Blood collection from the antecubital vein using a 21-gauge syringe.

ROS were determined using a previously described method [12–14]. Blood was centrifuged at 3000 rpm (0.65 g) for 10 min; serum was separated and analysed for the presence of ROS with the dROMs test (DIACRON, GR, Italy). Five microlitre of serum or standard was added to a solution containing 1 ml of acetate buffer (pH 4.8) and 10 µl of chromogen. After incubation at 37°C for 75 min, samples were analysed by spectrophotometry (Beckman DU640) at 505 nm wavelength. Results were calculated using the following formula:

Formula

All measurements were performed in a blinded way. Data are expressed in conventional units (U) and one unit corresponds to a concentration of 0.08 mg/dl hydrogen peroxide (H2O2).

The normal range is 200–300 U, while values >300 U indicate oxidative stress (oxidative stress threshold) [9, 10].

Data are presented as mean (SD). The comparison between groups was performed by a t-test and Wilcoxon test, on the basis of distribution of the data. Comparison between the changes within each group was done using a paired I-test.

All analyses were done using Intercooled Stata 6.0 for Windows (Statistics/Data Analysis, Stata Corporation, College Station, TX, USA). Statistical significance was established when P < 0.05.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
Subjects and controls were selected from a cohort of 296 workers. Those with conditions which could affect ROS levels in the systemic circulation, such as cancer, diabetes, hypertension, cardiovascular diseases, CVI, skin ulcers, recent infections, pregnancy, smokers and use of antioxidant substances or oestroprogestinics, were excluded from the study. Five males were also excluded because of their small number, compared to females.

The study population consisted of 55 operating theatre workers (Group 1), who stood at the operating table for >6 h during their shift (>90% of the working time), and 61 outpatient department nurses (Group 1 controls), who spent up to 3.5 h standing during their shift (~50%). We also enrolled 23 ironers (Group 2), who stood ironing for ~5 h during their shift (~75% of the working time), and 25 employed in the department store (Group 2 controls), who spent up to 3.5 h standing during their shift (~50%).

Standing workers and controls were comparable for age, sex, body mass index (BMI) and basal venous pressure of the lower limbs and basal ROS levels (P = NS).

In Group 1 (operating theatre nurses) and their controls, the increase in venous pressure after work on Day 1 without compression stockings was statistically significant (P < 0.001) but venous pressure after work was significantly higher in the study group (P < 0.001) compared to controls (Table 1). At the end of work, ROS levels significantly increased (P < 0.001) above the oxidative stress threshold (300 U) in Group 1 (P < 0.005) but not in controls. On the second day (using compression stockings), the variation of mean venous pressure and ROS levels after work was not statistically significant in both study Group 1 and controls.


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  		Table 1. Mean ± SD with 95% CI of venous pressure in lower limbs and reactive oxygen metabolites before and after working time in Group 1 and controls

 
Likewise in Group 2 (ironers) and their controls, the increase in venous pressure after work on Day 1 without compression stockings was statistically significant (P < 0.001) (Table 2). A non-statistically significant increase of ROS levels was observed in the ironers although ROS levels were significantly higher when compared to controls (P < 0.05). During the second day (wearing compression stockings), no increase in mean venous pressure or ROS levels was observed after work in both study group and controls and there was no difference between Group 2 and controls.


View this table:
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[in a new window]

  		Table 2. Mean ± SD with 95% CI of venous pressure in lower limbs and reactive oxygen metabolites before and after working time in Group 2 and controls

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
Our study showed that healthy workers who stood for prolonged periods during their working day had significantly higher levels of ROS after work than controls. We also showed that this increase could be prevented through the use of compression stockings.

In order to obtain homogeneous data about venous hypertension and oxidative stress, we studied two groups of healthy workers not affected by CVI and with well-characterized working conditions (female operating theatre nurses and industrial ironers) who stood for the majority of their working time (>6 h and up to 5 h respectively). Moreover, subjects enrolled as controls came from the same working environments, but had prolonged standing for less than half their working time.

According to emerging data, oxidative stress represents a risk factor not only for the onset and the evolution of CVI but also for other systemic diseases such as atherosclerosis, cancer and degenerative disorders [9–11]. Nevertheless, the role of oxidative stress in standing workers has never been previously investigated and similarly the efficacy of preventive measures is unknown.

We have already reported enhanced oxidative stress in patients with varicose veins [12, 13] and in healthy workers standing for >6 h during working time [14]. The goals of the present study were to assess how long healthy workers must stand during their shift to have significant oxidative stress and to evaluate the efficacy of compression stockings as a preventive measure against overproduction of ROS.

Compression stockings seem to be a useful and easy preventive measure against oxidative stress in healthy workers who stand for long periods, especially when other preventive measures, such as rest breaks, mini breaks or chances for ambulation while working, are not possible. On the basis of our data, the use of compressive stockings in healthy workers who stand for up to 5 h is unnecessary, as they have a non-significant ROS production after work. However, a larger number of workers with different amounts of upright position while working should be evaluated to obtain a reliable estimation of their risk.


Key points
  • Overproduction of ROS represents a risk factor for CVI as well as for other systemic diseases
  • Healthy workers who stand for >90% of their working time have increased production of ROS which is reversed through the use compression stockings
  • The use of compression stockings should be considered in workers who stand for prolonged periods when other preventive measures such as breaks and posture change are not possible.

 


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
The research was founded by an unrestricted grant by ISPESL (National Institute for Occupational Safety and Prevention).


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

  1. Jawien A. The influence of environmental factors in chronic venous insufficiency. Angiology (2003) 54(Suppl 1.):S19–S31.[Abstract/Free Full Text]

  2. Beebe-Dimmer JL, Pfeifer JR, Ewngle JS, et al. The epidemiology of chronic venous insufficiency and varicose veins. Ann Epidemiol (2005) 15:175–184.[CrossRef][Web of Science][Medline]

  3. Krijnen RM, de Boer EM, Ader HJ, et al. Venous insufficiency in male workers with a standing profession. Part 1: epidemiology. Dermatology (1997) 194:111–120.[Web of Science][Medline]

  4. Kontosic I, Vukelic M, Drescik I, et al. Work conditions as risk factors for varicose veins of the lower extremities in certain professions of the working population of Rijeka. Acta Med Okayama (2000) 54:33–38.[Medline]

  5. Ziegler S, Eckhardt G, Stoger R, et al. High prevalence of chronic venous disease in hospital employees. Wien Klin Wochenschr (2003) 115:575–579.[Web of Science][Medline]

  6. Bergan JJ. Chronic venous insufficiency and the therapeutic effects of Daflon 500 mg. Angiology (2005) 56:21–24.[CrossRef]

  7. Coleridge Smith PD. Deleterious effects of white cells in the course of skin damage in CVI. Int Angiol (2002) 21:26–32.[Web of Science][Medline]

  8. Khodabandehlou T, Boisseau MR, Le Devehat C. Blood rheology as a marker of venous hypertension in patients with venous disease. Clin Hemorheol Microcirc (2004) 30:307–312.[Web of Science][Medline]

  9. Fukai T, Folz RJ, Landmesser U, et al. Extracellular superoxide dismutase and cardiovascular disease. Cardiovasc Res (2002) 55:239–249.[Abstract/Free Full Text]

  10. Harrison D, Griendling KK, Landmesser U, et al. Role of oxidative stress in atherosclerosis. Am J Cardiol (2003) 91:7–11.[CrossRef]

  11. Migliore L, Coppede F. Genetic and environmental factors in cancer and neurodegenerative diseases. Mutat Res (2002) 512:135–153.[CrossRef][Web of Science][Medline]

  12. Pola P, Dal Lago A, Flore R, et al. Hyperproduction of oxygen free radicals in non complicated varicose disease of the lower limbs: preliminary data. J Vasc Invest (1998) 4:25–30.

  13. Flore R, Santoliquido A, Dal Lago A, et al. Long saphenous vein stripping reduces local level of reactive oxygen metabolites in patients with varicose disease of the lower limbs. World J Surg (2003) 27:473–475.[CrossRef][Web of Science][Medline]

  14. Flore R, Gerardino L, Santoliquido, et al. Enhanced oxidative stress in workers with a standing occupation. Occup Environ Med (2004) 61:548–550.[Abstract/Free Full Text]

  15. Byrne B. Deep vein thrombosis prophylaxis: the effectiveness and implications of using below-knee or thigh-length graduated compression stockings. Heart Lung (2001) 30:277–284.[CrossRef][Web of Science][Medline]

  16. Brandjes DP, Buller HR, Heijboer H, et al. Randomised trial of effect of compression stockings in patients with symptomatic proximal-vein thrombosis. Lancet (1997) 349:759–762.[CrossRef][Web of Science][Medline]

  17. Hirai M, Nukumizu Y, Kidokoro H, et al. Effect of elastic compression stockings on oedema prevention in healthy controls evaluated by a three-dimensional measurement system. Skin Res Technol (2006) 12:32–35.[CrossRef][Web of Science][Medline]

  18. Partsch H. Compression therapy in venous leg ulcers. How does it work? J Phlebol (2002) 2:129–136.

  19. Bartolo M, Antignani PL, Di Folca, et al. Mesure de la pression veineuse avec le Doppler: standardisation de la méthode. Phlébologie (1984) 37:97–101.[Medline]


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