Prevalence of chronic headache in shift workers in an industry

Introduction: Primary headaches and sleep disorders are closely related conditions. The global prevalence of chronic headache is estimated at 4.6%, while in Brazil it corresponds to 6.9%. Up to 50% of migraine patients report insomnia. This study evaluated the prevalence of chronic headache in workers and its association with fixed shift work, chronotype, and sleep. Methods: This is a cross-sectional, observational, and analytical study involving 354 fixed-shift workers via an electronic form. The prevalence of chronic headache by work shift was calculated, and Pearson's Chisquare tests and binary logistic regression were applied to express the degree of association between independent variables and the presence of chronic headache. Results: The prevalence of chronic headache was 12.43%. No statistical association was found between shifts and the disease (p>0.05), a finding consistent across subgroup analyses. Chronotype analysis revealed a strong dependence on shift (p<0.0001), evidencing a self-selection pattern (morning types in day shifts, evening/mixed types in night shifts). The most robust independent associated factors were analgesic overuse (OR: 13.7), irritability (OR: 3.5), and distractibility (OR: 2.4). Discussion: The absence of negative impact from shifts suggests a neurobiological resilience promoted by chronobiological alignment (behavioral self-selection) in fixed schedules. Headache chronicity in this population is independent of work schedule, being predominantly associated with modifiable factors. Conclusion: Chronic headache was characterized as independent of fixed shift work. Management, especially in refractory cases, should not be restricted to analgesia but incorporate active evaluation of diurnal symptoms and sleep disorders, aiming to mitigate comorbidities that perpetuate chronicity. (AU)