TABLE 2

Key studies detailing the epidemiology of inducible laryngeal obstruction (ILO)

Authors [reference]YearPopulationDesignFindingsComments
Hira and Singh [46]2009n=51
Patients referred to tertiary centre for treatment-refractory asthma
Cross-sectional24% had VCD
Age 32.9±12.4 years
58% female
IOS-positive in 58% of cases and 15% of controls
Only considers glottic ILO diagnosed at rest
Røksund et al. [2]2009n=151 cases and n=20 controls
Patients with exertional dyspnoea consecutively referred to a tertiary clinic
Cross-sectional75% had EILO
Age 16.3±7.3 years
72% female
Detailed description of laryngoscopic presentations
Highly selected population
Christensen et al. [21]2011n=98 (n=556 invited to participate)
General population
Cross-sectional43% had EILO
Age 19 (14–24) years
Female/male odds ratio of having EILO was 3.41
79% supraglottic, 14% glottic, 7% mixed glottic and supraglottic
70% had verified airway hyperresponsiveness to methacholine
Estimated prevalence of EILO in the general population: 7.6%
Selection bias from 2-day work-up
Nielsen et al. [6]2013n=88
Athletes referred to CLE in a tertiary asthma clinic
Case series35% had EILO
Median (IQR) age 18 (11) years 77% female
43% had verified asthma
Retrospective design
Highly selected population
Tilles et al. [103]2013n=143
Patients with EILO confirmed by post-exercise laryngoscopy
Case seriesAll EILO-positive (by design)
n=83 glottic (84% female); age 14±2.6 years
n=60 supraglottic (77% female); age 14±2.3 years
Retrospective design
Highly selected population
Post-exercise laryngoscopy
Marcinow et al. [104]2014n=46
Elite athletes and age- and sex-matched non-athletes, both with verified PVFMD
Case–controlAll PVFMD-positive (by design)
Age 21 (18–69) years
70% female
39% had verified asthma
Retrospective design
Highly selected population
Only glottic component considered
Hanks et al. [105]2012n=148
Athletes referred to a tertiary asthma clinic for evaluation of exertional dyspnoea
Cross-sectional70% of tested (n=82) had VCD
Median age 19 years
73% female
31% of VCD-positive subjects had verified EIB
6% had verified asthma
Retrospective design
Diagnosis by videolaryngostroboscopy
Johansson et al. [3]2015n=125 (n=2309 screened)
General population with exertional dyspnoea
Cross-sectional11% of cases and 4% of controls had EILO
Mean (range) age 14.2 (13–15) years
Estimated prevalence of EILO in the general population: 5.7% (equal for male and female) 44% of EILO-positive subjects had verified EIB
Well-designed
Did not report details on glottic/supraglottic components
Hilland et al. [58]2016n=20 (cases)
Patients with a history of childhood laryngomalacia requiring hospital admission
Case–control70% EILO-positive
Age 12.7±2.7 years
35% female
70% supraglottic
45% of EILO-positive subjects had anomalies at rest
Highly selected population
Walsted et al. [7]2016n=37
Patients with suspected asthma and exertional dyspnoea referred to a tertiary asthma clinic
Cross-sectional22% EILO-positive
Median (IQR) age 22.5 (12) years
100% female
88% supraglottic
14% of EILO-positive had verified asthma
Inspiratory flow in mannitol and methacholine tests were poor predictors of EILO
Selected population

Data are presented as mean±sd or median (range), unless otherwise stated. VCD: vocal cord dysfunction; IOS: impulse oscillometry; EILO: exercise-induced laryngeal obstruction; CLE: continuous laryngoscopy during exercise; IQR: interquartile range; PVFMD: paradoxical vocal fold motion disorder; EIB: exercise-induced bronchoconstriction.