Study design
This research used a cross-sectional observational design, aiming to investigate the prevalence and severity of auditory exostosis in Australian warm water surfers. The study was approved by the Bond University Human Research Ethics Committee (BUHREC 15221).
Participants
Surfers were recruited through advertising in a local paper and from local boardrider clubs in the Gold Coast (GC) area (City of Gold Coast, Queensland, Australia). Additional support for recruitment was obtained from surfing magazines, websites and local surf shops in the GC area. Participants or the public were not involved in the design, or conduct, or reporting, or dissemination of our research.
Eligibility criteria
Only individuals living and surfing in the GC region were considered to be included. Currently active surfers over 18 years of age, surfing all year round, with a minimum of 5 consecutive years of surfing experience, surfing at least five sessions per month, were invited to take part in the research. Surfers were excluded from the study if they had a history of exposure to cold water (mean temperature below 19 °C) for more than 3 consecutive weeks, if they participated for more than 3 consecutive weeks in winter sports activities (e.g., skiing, snowboarding), or if they have lived in cold regions (located more than 30° north or south of the equator) for more than 5 consecutive years in their lifetime. Additionally, participants were excluded if both the right and left EAC were occluded by cerumen.
Procedures
As described in our previous studies [19, 20], all participants who successfully passed the initial screening were invited to participate in this study. The research took place at the Water Based Research Unit (WBRU), Bond Institute of Health and Sport, Bond University, Gold Coast (Queensland, Australia). An explanatory statement and consent form were given to all participants upon arrival at the WBRU. Prior to providing written informed consent, all potential participants were given the opportunity to ask any questions about the research and about the testing procedure [19, 20]. The explanatory statement illustrated the exam to be conducted, and contained a simple overview of the research project and its purpose [19, 20]. The informed consent form was signed once participants were satisfied with the information provided.
At the WBRU, participants were asked to complete a questionnaire to collect basic demographic data and to examine their surfing habits and otological history, as described in our previous studies [19, 20]. After completing the questionnaire, and in line with the methodology previously adopted by our research team [19, 20], all participants underwent clinical examination of both ears, via otoscopy, by an experienced Sport and Exercise Physician, using a hand-held, battery-powered digital otoscope (Digital MacroView™, Welch Allyn®, USA), capable of acquiring digital images.
Predictors and outcome measures
Surfing characteristics
Surfers were assessed with regard to surfing specific characteristics, which included: surfing experience in years; average number of sessions per week; average number of hours per session; winter exposure in hours (number of hours per session during winter multiplied by number of sessions during winter and number of years surfing); surfing ability, as measured by the Hutt scale [21]; stance while surfing (i.e., ‘regular’ if left foot forward or ‘goofy’ if right foot forward); and main type of surfboard (short, mini-mal/funboard, or longboard). Additionally, they were asked whether they were involved in any other ocean sport.
Otological history
Participants were asked about the presence of otological symptoms (e.g., otalgia, hearing loss), regular use of prevention methods for EAE (e.g., ear plug, hood), and previous history of otitis externa (OE) and EAE.
Exostosis
During otoscopy, images of the EAC were recorded, and all images were assessed to determine the presence of EAE. If present, the degree of obstruction of the EAC was graded on the standard clinical one-to-three scale (Fig. 1; grade 1: up to 33% of obstruction; grade 2: between 34 to 66% of obstruction; grade 3: more than 67% of obstruction), as previously described [16].
Reliability
Initially, an intra-rater reliability study was conducted as a single clinician (Specialist) assessed the severity of exostosis in all participants. It is common practice to assess the intra-rater reliability of clinicians [22], particularly when the diagnosis and/or grading is subjective, as is with EAE [23]. A total of 15 EAE images were selected from a pool of approximately 970 images to determine the inter-rater reliability. The reliability between test-retest was 100% by the clinician. We then completed a quantification analyses where we utilized the freely available software ImageJ, developed by the National Institutes of Health (Bethesda, MD, USA), which is specifically designed for medical and/or biological analyses with a shown high validity (r = 0.988) and reliability (Cronbach’s alpha = 0.994) [24]. This software is used in a number of medical fields, including computerized tomography analyses, blood vessel diameter analyses, abdominal and skeletal muscle mass, and wound healing [25]. However, to the best of our knowledge, it has not previously been used in determining the severity of exostosis. However, we have recently shown this technique to have a high coefficient of reliability (r = 0.999), and a significant correlation (total area and exostosis area, p < 0.01, r = 0.999), and a near perfect positive relationship between repeated measurements [26]. Therefore, we deemed this quantification technique of exostosis appropriate to assess the clinicians analyses of exostoses in our participants. There was 100% agreement between the clinician’s assessment of the severity of exostosis and our quantification method.
Data analysis
Continuous data were analyzed descriptively to determine means and standard deviations (SD) and tested for normality by assessing skewness, kurtosis, Q-Q plots, and the Kolmogorov-Smirnov test. Categorical outcomes were summarised using frequencies and percentages. A Chi-square test of independence was used to assess associations between the main outcome variables (EAE presence and severity) and categorical outcomes. The level of significance, alpha, was set a priori at 0.05 for all statistical tests. All analyses were performed with SPSS statistical software (Version 25.0 for Windows, SPSS Inc., Chicago, IL, USA, 2017).