Introduction On-shift napping can benefit night workers as regards sleep deprivation, adjustment of circadian rhythms, and alertness. But possible benefits of nap on health outcomes are scarcely investigated. Considering that night work is pointed as a risk factor for hypertension and obesity, we investigated the possible attenuation of blood pressure and body mass index increase by on-shift napping among nursing teams.

Methods A cross-sectional study was conducted in a public hospital in Rio de Janeiro, Brazil with nursing professionals who were informally allowed to nap for up to three consecutive hours during working nights. Current and accumulated doses of night work (NW) were studied through the number of working nights/2 week-span and years of NW, respectively. Four outcomes were measured using standard equipment and techniques: systolic blood pressure (SBP), diastolic blood pressure (DBP), hypertension (SBP ≥140 mmHg or DBP ≥90 mmHg or prescription of antihypertensive medication), and body mass index (BMI). The associations between exposure variables and outcomes were based on logistic regressions (hypertension) and generalised linear models (SBP, DBP and BMI).

Results Among non-nappers (but not among nappers), current doses of NW (number of working nights) was significantly associated with increased SBP (β-value=1.39; 95% CI: 0.31 to 2.49) and DBP (β-value=0.80; 95% CI: 0.10 to 1.50), as well as increased odds for hypertension (OR=3.35; 95% CI: 1.74 to 6.57). This association was not observed for accumulated doses of NW. As regards BMI, both current and accumulated doses of NW were significantly associated with increased BMI levels (β-value=0.364 [95% CI: 0.002 to 0.749] and β-value=0.092 [95% CI: 0.011 to 0.173], respectively) only among non-nappers.

Discussion Despite difficulties to the practice of napping on the job, the promising results for both BP and BMI justify further investigations that could subsidise policies related to promoting adequate conditions for night workers to nap while on the job.