Objectives To investigate the association between job strain, social support at work and insomnia among registered nurses.

Method A cross-sectional study was conducted among 3.229 nurses (87% women) in 18 major public hospitals in Rio de Janeiro/Brazil. Data collection was based on a comprehensive self-filled questionnaire that included questions on insomnia and the Job Content Questionnaire (JCQ). Job strain (high psychological demands and low control) and social support were evaluated by the Portuguese version of the 2.0-JCQ, defined by the quadrant approach. In addition, emotional demands were also assessed, so that high strain was evaluated considering separately the psychological and the emotional demands. Insomnia was defined as having at least one of the insomnia symptoms: difficulty initiating sleep, maintaining sleep or early morning awakening. Multivariate logistic regression and adjusted odds ratios and 95% confidence intervals were calculated.

Results The overall prevalence of insomnia was 34.3%. Individuals with high job strain and low social support experienced insomnia more frequently (p < 0.05). After adjusting for socio-demographic, work and health-related variables, high strain doubled the chances of presenting insomnia considering both the psychological (OR=2.20, CI 1.74–2.78) and the emotional demands (OR=1.99, CI 1.57–2.53). High strain in combination with low support at work increased the chances of insomnia even more.

Conclusions High strain is suggested as a possible risk factor for insomnia considering both psychological and emotional demands. The lack of social support from co-workers and supervisors seem to potentiate the odds for insomnia.