Sustained body weight reduction by an individual-based lifestyle intervention for workers in the construction industry at risk for cardiovascular disease: Results of a randomized controlled trial
Introduction
Cardiovascular disease (CVD) is the number one cause of death globally (World Health Organization, 2009). The main precursors of CVD are smoking, obesity, hypertension, and a disturbed serum lipid profile (MacMahon et al., 1990, Yusuf et al., 2004). The latter three precursors are to a large extent influenced by an unhealthy diet (Lucas et al., 2005, Mensink and Katan, 1992, Mente et al., 2009) and insufficient physical activity (Blair et al., 1989, Klein et al., 2004, Lee et al., 2003). Smoking is an independent CVD risk factor, and also leads to hypertension and a disturbed serum lipid profile (Chelland et al., 2008, Mancia et al., 1990). Improving lifestyle is not only beneficial for health, but may also prevent absenteeism and high costs for the employer (Goetzel et al., 2010, Proper et al., 2006, Van Duijvenbode et al., 2009). Thus, a lifestyle intervention for workers at risk for CVD is considered potentially advantageous for workers as well as employers. Based on a systematic review of the literature, Groeneveld et al. (2010) concluded strong evidence for an effect on body weight among workers with an elevated risk of CVD (Groeneveld et al., 2010).
Three aspects need further investigation. First, data on the effectiveness of lifestyle interventions among workers in the construction industry, including both blue- and white-collar workers, are scarce. Most trials on diet and physical activity were aimed at white-collar workers only. Another gap to be filled in workplace lifestyle intervention research is related to the sustenance of changes in CVD risk factors. Not until an improved lifestyle is sustained over a longer term, the risk of CVD is permanently reduced. However, in most workplace lifestyle intervention studies, the final follow-up measurement took place directly after the intervention had ended (Connell et al., 1995, Nilsson et al., 2001, Proper et al., 2003). The last issue to be dealt with is which intervention strategy to use. Individual counseling was shown to be effective in numerous studies (Lemmens et al., 2008, Petrella and Lattanzio, 2002, Wadden et al., 2004). A counseling style frequently used nowadays is motivational interviewing (MI) (Miller and Rollnick, 2002). Although originally developed for use in substance abuse therapy, in recent years it has been proven effective in several lifestyle intervention studies (Rubak et al., 2005, Van Dorsten, 2007), although many studies on this topic were of poor quality (Knight et al., 2006). In the workplace intervention studies in which this counseling strategy was used (Elliot et al., 2007, Prochaska et al., 2008) body weight was evaluated, but blood pressure and cholesterol were not.
In the Health under Construction study, we developed an individual-based lifestyle intervention for workers in the construction industry in the Netherlands with an elevated risk of CVD. In Dutch construction industry, most workers are male and over 40 years of age. In 2008, the prevalence of overweight and obesity among male workers in the construction industry who attended the periodical health screening at the occupational health service was higher than among the total Dutch adult male population; 63.8% versus 52.3% (Statistics Netherlands, 2009). Based on the Framingham risk score, more than a quarter of male workers in the construction industry had a higher than moderate 10-year risk of coronary heart disease. In the Health under Construction study, we investigated the effectiveness of the intervention on short- and long-term changes in lifestyle. Significant favorable effects were found for snack intake at 6 and 12 months, and for fruit intake at 6 months. Physical activity had substantially increased in both intervention and control group at 6 months (+ 172 vs. + 94 min per week) and at 12 months (+ 129 vs. + 84 min per week), although the intervention effect was not significant. Quit rates in the intervention vs. control group were 31.1% vs. 13.4% at 6 months (OR for smoking 0.3, 95% CI 0.1; 0.7), and 23.7% vs. 19.5% at 12 months (OR 0.8, 95%CI 0.4; 1.6) (unpublished data). In the present article, we describe the short- and long-term effects of the Health under Construction study on body weight, blood pressure, cholesterol, and hemoglobin A1c (HbA1c).
Section snippets
Study population
Male workers in the construction industry aged 18–65 with an elevated risk of CVD were invited to the study, based on the results of their most recent periodical health screening. A worker was considered eligible for the study in case of a higher than moderate 10-year risk of coronary heart disease based on the Framingham risk score (Wilson et al., 1998), and having one or more additional risk factors, i.e. body mass index (BMI) ≥ 30; HbA1c ≥ 6.5%; not meeting the physical activity guidelines;
Results
In Fig. 1, a flow diagram of the study population is presented. Between March 2007 and March 2008, 816 workers provided informed consent. Between September 2007 and March 2009, all follow-up measurements took place. 517 participants provided data on one or more variables at all three time points, and were used for analyses. No adverse events of the intervention were reported. In Table 1, the baseline characteristics of the study population are presented. The residuals of all variables were
Principal findings
We aimed to find out the short- and long-term effects of a 6-month lifestyle intervention among workers in the construction industry with an elevated risk of CVD. Among participants who had aimed at smoking cessation, no significant changes in CVD precursors were found. Among the participants who had focused at improving diet and physical activity, a 2-kg difference in body weight was concluded at 6 and 12 months. Significant intervention effects were also found for HDL cholesterol and HbA1c at
Conclusion
This is the first study showing that an individual-based intervention using motivational interviewing techniques for workers in the construction industry can result in sustained beneficial changes in body weight. This is an important finding for occupational health, considering the rising prevalence of obesity and CVD in the aging male working population.
Conflict of interest statement
The authors declare that there is no conflict of interest.
Acknowledgments
We would like to thank Mr. VH Hildebrandt, MD, PhD, of TNO Department Quality of Life, for his advice in the development of the intervention. We are grateful to Mr. DP Peters for proof reading and editing the manuscript. We are grateful to Stichting Arbouw for covering the costs of this study.
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