Groeneveld et al. BMC Public Health 2011, 11:836 http://www.biomedcentral.com/1471-2458/11/836 Background In the Netherlands, among men aged younger than 65 years, a quarter of all deaths is due to cardiovascular diseases (CVD) [1]. Cardiovacular disease may not only lead to premature death, but also to decreased physical functioning and lower quality of life [2]. Important pre- cursors of CVD are obesity, hypertension, and an abnor- mal blood lipid profile. These abnormalities are caused to a large extent by an unhealthy lifestyle, such as unhealthy diet [3], insufficient physical activity (PA) [4], and smoking [5]. Irrespective of other CVD risk factors such as age, male gender, family history, or low job con- trol [6], improving lifestyle will lower CVD risk. Effec- tive lifestyle change strategies should be developed in order to prevent CVD. Numerous trials have been performed among persons with an elevated CVD risk, assessing the effectiveness of interventions aimed at changing lifestyle [7-9]. Different strategies have been evaluated, among which providing advice, exercise classes, a prescribed diet, and individual counseling. Advice alone was proven to be less effective than individual counseling in achieving long-term behavior change among adults with an elevated CVD risk [8,9]. Supervised exercise and diet alone may facilitate body weight loss [10], but long-term behavior change is less likely if not combined with more intensive diet and PA modification therapy [11], such as individual counseling. Nowadays, a frequently used counseling method is motiva- tional interviewing (MI). Motivational interviewing was originally developed for changing addictive behaviors, but has also proven effective in lifestyle change [12,13]. Moti- vational interviewing is a client-centered, directive method for enhancing intrinsic motivation to change by exploring and resolving ambivalence, and is based on the principle that behavior change occurs in stages [14]. During MI, determinants are addressed that have consistently proven associated with behavior change, such as attitude and self- efficacy [15]. The workplace is an appropriate setting for investigating lifestyle interventions, since many adults of various socio- economic statuses, lifestyles, and risk profiles can be tar- geted at once. Moreover, in the working population, a life- style intervention will not only influence CVD risk. Improving diet and increasing PA may also lower absen- teeism [16]. Regular PA may increase work ability, due to its effects on cardiorespiratory and musculoskeletal capa- city, factors that normally decline with age [17]. However, in most workplace lifestyle intervention studies, the suste- nance of health effects, which is necessary for permanent CVD risk reduction, was not determined, as the final fol- low-up measurement took place directly after the inter- vention had ended [18,19]. Recently, two workplace intervention studies were performed on the effectiveness Page 2 of 9 of MI on lifestyle changes [20,21], showing that MI is more effective than providing health risk information only, and equally effective to group activities or computer-tai- lored advice. Again, in both studies, no long-term follow- up measurements took place. In the Health under Construction study, we aimed to develop and evaluate a lifestyle intervention for construc- tion workers with an elevated CVD risk in the Nether- lands. In this population, most workers are male and over 40 years of age. In 2008, the prevalence of overweight and obesity among male construction workers who attended a periodical health screening at the occupational health ser- vice was higher than in the total Dutch adult male popula- tion; 63.8% versus 52.3% [22]. According to the Framingham risk score [23], 27.3% of male construction workers had a higher than moderate 10-year risk of coron- ary heart disease. In the Health under Construction study, we evaluated the short- and long-term effects on PA, diet, and smoking of a lifestyle intervention consisting of indivi- dual counseling using MI techniques among male workers in the construction industry with an elevated risk of CVD in the Netherlands. Methods Participants All male construction workers aged 18-65 years, employed at different (>400) companies throughout the Netherlands, who had attended the voluntary periodical health screening at the occupational health service between January 2007 and February 2008 (59.4% of all invited), and who had an elevated risk of CVD (n = 4.058; 19.1% of all screened), were personally invited to the study. Elevated CVD risk was concluded if the work- er’s 10-year coronary heart disease risk was higher than moderate according to the Framingham risk score, and he additionally fulfilled at least one of the following cri- teria; body mass index (BMI) ≥ 30 kg/m2; HbA1c ≥ 6.5%; consuming ≥ 35 glasses of alcohol per week; not meeting the Dutch PA guidelines; heart complaints; psy- chological complaints. The Medical Ethics Committee of the VU University Medical Center approved the study protocol. An extensive description of the study design is provided elsewhere [24]. Randomization, blinding, and sample size calculation The workers who consented to participate were pre-stra- tified for work type (blue-collar workers performing the construction work versus white-collar workers involved in administration and supervision), and individually ran- domized into the control or the intervention group, using Random Allocation Software (Version 1.0). After rando- mization, the research assistant notified each participant to which group he had been allocated. The investigator