Brazil’s night shift workers face a higher risk of health problems, unhealthy lifestyles, and exposure to dangerous occupational carcinogens compared to daytime workers, reveals a new nationwide study published in 2025. Researchers analyzed data from nearly 48,000 employed adults and found clear associations between night shift work and sleep disorders, tiredness, depression, poor diet, obesity, and contact with cancer-causing agents at the workplace.
These findings come at a critical time as night shift jobs grow worldwide, driven by industries requiring 24/7 operations. The study highlights urgent needs for workplace interventions, health education, and policies supporting the well-being of this vulnerable labor force.
What the Study Did
The research team used data from Brazil’s 2019 National Health Survey, a large, representative household study conducted by the Ministry of Health and the Brazilian Institute of Geography and Statistics (IBGE). They focused on 47,953 workers aged 18 to 59, identifying 6,599 who regularly worked night shifts (between 8 pm and 5 am).
Using sophisticated analysis, researchers examined how night shift work related to common health problems, lifestyle habits, and occupational exposures known to increase cancer risk. Importantly, they distinguished findings by gender to reveal differing risks and behaviors among male and female night workers.
Key Findings: Who Works Nights and What It Means for Their Health
Table 1 below outlines the prevalence of night shift work by demographic characteristics:
| Sociodemographic Group | Night Shift Workers (%) | Odds Ratio (OR)* | Significance (p-value) |
|---|---|---|---|
| Total Workers | 13.8 | – | – |
| Male | 17.0 | 1.90 | p < 0.01 |
| Female | 9.7 | 1.00 (Reference) | – |
| Age 18–29 | 14.4 | 1.17 | 0.01 |
| Age 30–39 | 15.1 | 1.25 | p < 0.01 |
| Urban Residents | 14.6 | 2.08 | p < 0.01 |
| Rural Residents | 7.6 | 1.00 | – |
| Per Capita Income > 2 MW | 17.4 | 2.39 | p < 0.01 |
*Odds ratios compare likelihood of night shift work within groups.
Men, urban residents, and higher-income workers were significantly more likely to work night shifts. The 30–39 years age group had the highest prevalence.
Night Workers Face More Sleep Problems, Fatigue, and Depression
Night shift workers reported more sleep disturbances and tiredness than their daytime counterparts. Female night workers exhibited a higher prevalence of depressive feelings.
Table 2 shows health problems associated with night work by gender:
| Health Problem | Male Night Workers (%) | Male Day Workers (%) | OR (95% CI) | Female Night Workers (%) | Female Day Workers (%) | OR (95% CI) |
|---|---|---|---|---|---|---|
| Sleep Disorders | 13.9 | 10.4 | 1.39 (1.17–1.65) | 22.4 | 19.1 | 1.23 (1.03–1.46) |
| Tiredness | 13.6 | 8.6 | 1.68 (1.41–2.00) | 24.2 | 19.8 | 1.29 (1.08–1.54) |
| Depressive Feelings | 5.0 | 4.0 | 1.25 (0.95–1.63) | 14.6 | 11.3 | 1.35 (1.09–1.67) |
| Obesity | 21.2 | 16.0 | 1.41 (1.20–1.66) | 11.0 | 9.4 | 1.18 (0.98–1.43) |
Night shift men were 41% more likely to be obese compared to day workers. Women night workers showed significantly more depressive symptoms, which may relate to caregiving responsibilities outside work.
Unhealthy Habits More Common Among Night Workers
Night time work was closely linked to poor dietary habits and increased substance use.
- Both male and female night workers consumed more unhealthy foods, sugary drinks, and frequently replaced meals with snacks.
- Female night workers smoked more regularly than their daytime peers.
- Alcohol consumption at least once a week was higher in male and female night workers.
These behaviors may reflect attempts to cope with fatigue, stress, and disrupted circadian rhythms but increase risks for obesity, cardiovascular disease, and cancer.
More Exposure to Occupational Carcinogens at Night
Night shift workers had markedly higher exposure to hazardous materials linked to cancer:
- Handling radioactive material: men 2.45 times, women 3.89 times more likely.
- Handling biological materials such as blood: men 3.18 times, women 3.89 times more likely.
- Women night workers were also 1.54 times more likely to be exposed to chemical carcinogens and 1.45 times more likely to suffer passive smoking at work.
What This Means and Recommendations
This groundbreaking study confirms night shift work poses multiple health challenges. These include sleep disruption, mental health strain, risky behaviors, obesity, and increased exposure to potentially cancer-causing workplace substances.
To protect Brazil’s night shift workers and similar populations worldwide, experts recommend:
- Workplace health programs emphasizing healthy nutrition and stress management.
- Reducing exposure to carcinogens with improved safety protocols and protective equipment.
- Smoking cessation and alcohol reduction campaigns tailored to night workers.
- Implementing work schedules that minimize circadian disruption.
- Health monitoring with regular check-ups focused on the unique risks of night work.
Summary Table 3: Unhealthy Behaviors and Occupational Risks Among Night Workers
| Risk Factor | Male Night Workers OR (95% CI) | Female Night Workers OR (95% CI) |
|---|---|---|
| Regular unhealthy food intake | 1.28 (1.12–1.46) | 1.32 (1.11–1.56) |
| Frequently replacing meals with snacks | 2.52 (1.66–3.83) | 2.15 (1.38–3.34) |
| Smoking | 1.01 (0.87–1.17) | 1.32 (1.10–1.59) |
| Alcohol consumption (weekly) | 1.15 (1.02–1.29) | 1.48 (1.23–1.78) |
| Handling radioactive material | 2.45 (1.61–3.72) | 3.89 (3.15–4.80) |
| Exposure to biological agents | 3.18 (2.45–4.12) | 3.89 (3.15–4.80) |
| Exposure to chemical substances | 1.05 (0.90–1.23) | 1.54 (1.20–1.97) |
| Passive smoking at work | 1.17 (0.93–1.46) | 1.45 (1.12–1.86) |
In Conclusion
As night shift work continues to expand with global economic demands, the health burden on these workers needs urgent attention. The Brazilian study provides robust evidence that night workers face more health problems and greater carcinogen exposures than day workers, underscoring the need for targeted policies, workplace safety improvements, and health promotion efforts.
Better understanding and managing the unique challenges of night shift work can help protect millions of workers worldwide from serious health risks, improving quality of life and reducing future disease burdens.
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