Among the various causes of mortality, deaths attributable to cardiovascular diseases (CVD) are the most widespread worldwide. Despite major progress being made, the risk remains. Occupational factors such as shift work have emerged as potential CV risk factors. With around 15 to 20% of workforce engaging in nightshift work in modern society for obvious economic and social reasons, the consequences of which on occupational and social inequalities are substantial. Compared to day workers, it was reported higher risks of cardiovascular diseases (estimated at 40%) and of metabolic syndrome (1.5 times) in shift workers. The occurrence of metabolic syndrome increases the risk to develop high blood pressure, diabetes and cardiovascular events. Because some characteristics of night work are potentially modifiable, some preventive strategies could be applied to reduce its adverse effects. For shift workers, some recent guidelines (High Health Authority, 2012) and fruitful literature propose to develop regular assessments of cardiovascular risk factors and occupational activities, and stress the need to expand preventive strategies. Moreover, some recent French laws provide an opportunity to implement preventive interventions and specific monitoring through the occupational physicians network. However, whether the concept is defined, the exact content, method and the potential benefits are unknown. The investigator assume that individual advice related to collective countermeasures referenced on guidelines (applied on worksite within plant) could lead a better improvement on incidence of metabolic syndrome compared to those that benefit only individual advice.

* Research objectives Main objective: To measure the benefit from implementation of individual and collective prevention (dispensed in worksites within plants) on metabolic syndrome compared to strategy relying only on individual prevention among night workers, over 2 years' follow-up. The secondary objectives of the study are to evaluate in both groups: 1) Observance of different types of preventive strategies 2) Impact of observance of preventive advice on metabolic syndrome in shift workers and on each component of metabolic syndrome 3) Determinants which promote the up-take of preventive strategies among night workers 4) The countermeasures which could be applied and effective within company 5) Medico-economic assessment is planned from an ancillary study.
* Methodology This study is designed as a multicenter, cluster randomized interventional controlled trial, to reduce the incidence of metabolic syndrome among night workers. Randomization will be performed on 100 occupational physicians (volunteers to participate), to apply one of both interventions. 3056 volunteers' night workers will be recruited from the employees regularly monitored by each physician during the routine medical monitoring. Two parallel groups will be performed: control group and experimental group. A two-year follow-up will be organized including check-points every 6 months. Control group: Every 6 months (T0, 6, 12, 18 months), standardized preventive individual advice focused on cardiovascular risk in night workers will be delivered by occupational physicians. Experimental group: In addition to this individual advice, preventive interventions dispensed on worksite will be carried out. Counter-measures will be applied by occupational health team to improve working conditions. By using a self-questionnaire, a medical questionnaire, a medical examination, biological sample, and specific follow-up of preventive interventions, the assessments will be performed. Study Primary outcome: Reduction of incidence of metabolic syndrome between the two groups (control and experimental) over 2 years' follow up.

Descriptive analysis according to the clusters and also to the both groups will be provided. Multivariate analysis, according to specific design of study (clusters), will be performed by multilevel analysis or marginal analysis. Given the specificity of self-employed people belonging to 'Regime social des independents, a target population will be added. The medical monitoring and individual prevention will be carried out by occupational physicians from occupational disease centres.

• Expected results From implementation of preventive strategies, investigator will expect: 1) The health improvement among night workers by decreased incidence of metabolic syndrome; by improved quality of life; 2) A improvement of social and professional development of night workers by a better tolerance of night work, and job retention; 3) Behavioral improvement by a positive impact of individual and collective behavioral changes on cardiovascular risks; 4) Practical actions by identifying factors which influence the implementation of preventive actions; 5) By this project, investigator would like also to determine some relevant, practical and effective actions which could be generalized at all night workers in preventive health public Policy.