Re: The Association Between Hay Fever and Stroke in a Cohort of Middle Aged and Elderly Adults

To the Editor: We read with interest the paper by Matheson et al¹ on the increased risk of stroke in those with hey fever (allergic rhinitis). The authors suggested the mechanism to be the systemic inflammation found in those with allergic rhinitis. We would suggest an additional explanation, ie, obstructive sleep apnea (OSA), for the increased risk.

Allergic rhinitis was associated with increased risk of OSA in adults² and children.³ Nasal blockage caused by allergic rhinitis would lead to mouth breathing. Chronic mouth breathing will predispose to a steep mandibular plane that results in a narrow upper airway. A narrow upper airway would predispose to OSA. OSA with apnea-induced hypoxia and exaggerated negative intrathoracic pressure, arousals from sleep, surges in blood pressure, alteration in autonomic nervous activity, as well as production of reactive oxygen species, vascular endothelial growth factor, and inflammatory mediators are factors contributing to the vascular consequences. OSA is associated with atherosclerosis in adults.⁴ Adults with OSA had an increased risk of cerebrovascular disease independent of atherosclerotic risk factors.⁵

Recent researches of OSA found that inflammation was involved in the process.⁶ C-reactive protein (CRP) had been shown to increase even in children with OSA. CRP dropped after tonsillo-adenoidectomy in children.⁷ Other factors that might be involved in atherosclerosis, like fibrinogen level and p-selectin (marker of platelet activation), were shown to be higher in those with OSA.

Another potentially important factor is excessive daytime sleepiness. Allergic rhinitis⁸ was strongly associated with excessive daytime sleepiness (EDS). EDS is a well known risk factor for stroke in middle age and elderly. Previous studies showed that EDS, even after adjusted for the effect of sleep disordered breathing, is associated with stroke.⁹

In conclusion, allergic rhinitis is a very common condition that is associated with OSA that carries a high risk of mortality and morbidities. Appropriate treatment of childhood allergic rhinitis may prevent the development of OSA by preventing chronic oral mouth breathing. Adults with allergic rhinitis and habitual snoring should undergo a sleep polysomnography study as to allow diagnosis and treatment of OSA. Failure to do so may result in stroke as demonstrated by Matheson et al.¹