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congestion, daytime somnolence, and sleep quality. 2029 INCS are also thought to improve sleep quality by reducing proinflammatory cytokines, which have been shown to negatively impact sleep. 2030 There have been 5 RCTs assessing the efficacy of INCSs on nasal congestion and sleep. 673,706,707,1275,1276 The results of all 5 studies demonstrated an improvement in sleep quality and sleep-related QOL metrics. A meta-analysis by Weiner et al. 1297 found that INCSs were more effective than oral antihistamines at treating nasal blockage, although there was no significant differences between treatments on nasal resistance. The pharmacologic interventions used in the treatment of AR may also have consequences on sleep. The first-generation H 1 antagonists are known to cause sedation due to the capability of crossing the blood-brain barrier and acting as a depressant on the central nervous system leading to drowsiness. 2031 While this may be a desirable side effect at bedtime, it is an undesirable consequence for daytime symptom management. The second generation H 1 antagonists have less propensity for crossing the blood-brain barrier and are therefore less sedating. Fexofenadine and loratadine are reported as the least sedating oral antihistamine treatment options. 2032,2033 Patients should be counseled regarding the potential for sedation when taking oral H 1 antihistamines. There has been 1 RCT study looking at pseudoephedrine (taken in the morning) and the impact on sleep quality, daytime somnolence, and fatigue. The study found no significant negative or positive impact on all measures compared to placebo. 2030 There was a statistically significant beneficial effect on nasal congestion. The impact of AR on sleep should be assessed by history, sleep and QOL questionnaires, and careful physical examination. A standard treatment algorithm for symptomatic management of AR should be effective at improving the symptoms which adversely affect sleep. INCSs are the most effective pharmacologic therapy for alleviating nasal congestion. Patients treated with oral antihistamines should be mindful of the potential for sedation. • Aggregate Grade of Evidence: B (Level 1b: 5 studies; Level 2b: 1 study; Level 2c: 5 studies; Level 3b: 7 studies; Level 4: 2 studies; Table X.K).

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XI. Knowledge gaps and research opportunities

The existing literature related to AR is quite deep in certain areas but notably lacking in others (Table XI). We continue to see more and more citations related to AR every year, yet the process undertaken to produce this ICAR:AR document has identified some important knowledge gaps. The sections below highlight the need for future research related to specific aspects of AR.

XI.A. Epidemiology and risk factors

Studies have previously been undertaken to determine the prevalence of AR in various parts of the world. While the data from these studies is often quoted, it is limited by its methodology relating primarily to surveys (sometimes complemented by allergen sensitivity testing). Our world is better connected by technology today than it had been previously. We

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.