Table 3 Risk factors associated with SIPE
References | Study design | Subjects | Sample size and description | Type of exposure | Case definition | Case ascertainment method | Exposures investigated | Findings | Quality of evidence (see Additional file 4 for more detail) | |
|---|---|---|---|---|---|---|---|---|---|---|
Personal characteristics | Environmental factors | |||||||||
Miller et al. [19] | Case- control | Triathletes | 1400 members of USA Triathlon plus additional 11 cases (31 cases, 1380 controls) | Varying | Cough productive of pink frothy or blood-tinged secretions | Survey of USA Triathlon members plus 11 cases from slowtwitch.com | Age, sex, hypertension, diabetes, use of multivitamins, vitamin C, vitamin E, fish oil, flax oil, swimming skill, warm up, pre-swim hydration | Wetsuit use, climate trained in, open water/pool, course distance | Significant risk factors were hypertension, female sex, fish oil use and long course distance. | Self-reported non-validated tool to detect SIPE cases. Limited statistical power due to relatively small sample size. Unclear when health conditions were diagnosed and if medication being taken |
Shupak et al. [13] | Prospective incidence study | Military trainees (Israeli Navy) | 35 males aged 18–19 performing 5 swimming trials (2.4–3.6 km) over 2 months (mid-Jan to mid-Mar). Trials were ≥ 1 week apart | Moderately cold open sea, (16–18 °C), diving jackets, supine position with fins | When, in the absence of prior seawater aspiration, the swimmer reported shortness of breath accompanied by coughing | Post-swim questionnaire completed by all trainees | Lung function, level of exertion | None investigated | Lung volume and mid-expiratory flow measured 12 months earlier was significantly lower in SIPE susceptible group compared to asymptomatic group. No correlation between level of exertion and occurrence of SIPE | Self-reported non-validated tool to detect SIPE cases. Long period of time between screening and field study measurements. Limited statistical power due to relatively small sample size |
Moon et al. [23] | Clinical trial | Triathletes, divers and one windsurfer | 30 participants: 22 males, 8 females (10 cases, 20 controls) | Varying | No case definition provided | Not reported | Haemodynamics and gas exchange measurements | None investigated | SIPE group had significantly higher MPAP and PAWP, and lower tidal volume during immersed exercise | Cases had a higher proportion of females and may have been physically fitter. Inconsistency in the way pre-exercise measurements were taken between cases and controls |