Reconsidering screening thresholds in health assessments for obstructive sleep apnea using operational and safety incident data.

The rail industry in Australia screens workers for probable obstructive sleep apnea (OSA) due to known safety risks. However, existing criteria to trigger screening only identify a small proportion of workers with OSA. The current study sought to examine the relationship between OSA risk and rail incidents in real-world data from Australian train drivers, and conducted a proof of concept analysis to determine whether more conservative screening criteria are justified. Health assessment (2016-2018) and subsequent rail incident data (2016-2020) were collected from two passenger rail service providers. Predictors included OSA status (confirmed no OSA with a sleep study, controlled OSA, unknown OSA [no recorded sleep assessment data] and confirmed OSA with no indication of treatment); OSA risk according to the current Standard, and OSA risk according to more conservative clinical markers (BMI threshold and cardiometabolic burden). Coded rail safety incidents involving the train driver were included. Data were analysed using zero-inflated negative binomial models to account for over-dispersion with high 0 counts, and rail safety incidents are reported using Incidence Risk Ratios (IRRs). A total of 751 train drivers, typically middle-aged, overweight to obese and mostly men, were included in analyses. There were 43 (5.7%) drivers with confirmed OSA, 62 (8.2%) with controlled OSA, 13 (1.7%) with confirmed no OSA and 633 (84.4%) drivers with unknown OSA. Of the 633 train drivers with unknown OSA status, 21 (3.3%) met 'at risk' criteria for OSA according to the Standard, and incidents were 61% greater (IRR: 1.61, 95% Confidence Interval (CI) 1.02-2.56) in the years following their health assessment compared to drivers who did not meet 'at risk' criteria. A more conservative OSA risk status using lower BMI threshold and cardiometabolic burden identified an additional 30 'at risk' train drivers who had 46% greater incidents compared to drivers who did not meet risk criteria (IRR (95% CI) 1.46 (1.00-2.13)). Our more conservative OSA risk criteria identified more workers, with greater prospective incidents. These findings suggest that existing validated tools could be considered in future iterations of the Standard in order to more sensitively screen for OSA.

Comparison of Urine and Oral Fluid for Workplace Drug Testing.

AIMS: To determine the relative detection rates of urine versus oral fluid testing in a safety sensitive industry and the correlation with diagnosed substance use disorders and possible impairment at work. METHODS: The trial involved 1,500 paired urine and oral fluid tests performed in accordance with Australian Standard/New Zealand Standard (AS/NZS) 4308:2008 and AS 4760:2006. Workers who returned a positive test were screened for substance use disorders, as defined by DSM-5, and for possible impairment at work following that particular episode of substance use. RESULTS: Substances were detected in 3.7% (n = 56) of urine samples and 0.5% (n = 8) of oral fluid samples (p < 0.0001). One worker (0.07%) had a substance detected on oral fluid alone versus 49 workers (3.3%) who had substances detected on urine alone. Twelve workers returned a positive result, defined as being consistent with the use of an illicit drug or a controlled substance without a clinical indication and prescription. Nine workers tested positive on urine alone, one on oral fluid alone and two on both (p = 0.0114). Of note, 6/11 workers who tested positive on urine had possible impairment at work and 2/11 had a substance use disorder versus 2/3 and 0/3, respectively, who tested positive on oral fluid. CONCLUSIONS: Urine drug testing performed in accordance with AS/NZS 4308:2008 is more likely to detect overall substance use and illicit drug use than oral fluid testing conducted in accordance with AS 4760:2006. Urine testing performed in accordance with AS/NZS 4308:2008 may also be more likely to detect workers with possible impairment at work and substance use disorders than oral fluid testing performed in accordance with AS 4760:2006.

Color Vision and the Railways: Part 1. The Railway LED Lantern Test.

PURPOSE: Lantern tests and practical tests are often used in the assessment of prospective railway employees. The lantern tests rarely embody the actual colors used in signaling on the railways. Practical tests have a number of problems, most notably consistency of application and practicability. This work was carried out to provide the Railway LED Lantern Test (RLLT) as a validated method of assessing the color vision of railway workers. METHODS: The RLLT, a simulated practical test using the same LEDs (light-emitting diodes) as are used in modern railway signals, was developed. It was tested on 46 color vision-normal (CVN) and 37 color vision-deficient (CVD) subjects. A modified prototype was then tested on 106 CVN subjects. RESULTS: All 106 CVN subjects and most mildly affected CVD subjects passed the modified lantern at 3 m. At 6 m, 1 of the 106 normal color vision subjects failed by missing a single red light. All the CVD subjects failed. The RLLT carried out at 3 m allowed mildly affected CVD subjects to pass and demonstrate adequate color vision for the less demanding railway tasks. Carried out at 6 m, it essentially reinforced normal color vision as the standard. CONCLUSIONS: The RLLT is a simply administered test that has a direct link to the actual visual task of the rail worker. The RLLT lantern has been adopted as an approved test in the Australian National Standard for Health Assessment of Rail Safety Workers in place of a practical test. It has the potential to be a valid part of any railway color vision standard.

Color Vision and the Railways: Part 2. Comparison of the CN Lantern Used on the Canadian Railways and Railway LED Lantern Tests.

PURPOSE: There are two currently available lantern tests that have their design based solely on the practices of the rail industry. These are the CN Lantern (CNLAN) used on the Canadian Railways and the Railway LED Lantern Tests (RLLT). In the same way that the signaling practices differ in the two jurisdictions, the design of the lanterns also differ. The CIE (Commission Internationale de l'Éclairage)-recommended color vision standards for transport predate both lanterns. The study was undertaken to assess the appropriateness of these lanterns in CIE Color Vision Standard 1. CIE Standard 1 is called "Normal color vision" but some very mild anomalous trichromats may pass the specified "lantern test that presents a high level of difficulty." METHODS: The lantern tests were undertaken by 46 color vision-normal and 37 color vision-deficient subjects. RESULTS: Subjects made more errors on the RLLT, and the pattern of errors is different, partly because there are blank presentations in the RLLT and "no light" is an acceptable response. The two lanterns showed agreement on the pass/fail categorization of 73 of the 83 subjects. The RLLT fails more color vision-normal subjects. CONCLUSIONS: Despite the different construction principles, the RLLT and CNLAN have pass/fail levels that are comparable with the Holmes-Wright Type B lantern, which is nominated in CIE Color Vision Standard 1 but is no longer commercially available. The higher failure rate of color vision-normal subjects on the RLLT has been addressed by changing the intensities of the two darkest red lights.

Color Vision and the Railways: Part 3. Comparison of FaLant, OPTEC 900, and Railway LED Lantern Tests.

PURPOSE: The Farnsworth Lantern (FaLant) and the OPTEC 900 are nominated in the Commission Internationale de l'Éclairage (CIE) Color Vision Standard 2. Neither test uses the railway signal color code of red, yellow, and green, and only the OPTEC 900 is commercially available. The Railway LED Lantern Test (RLLT) is based on railway signaling practices in New South Wales, Australia, and is nominated in the Australian railway medical standard. The objective of this study is to compare the performance of the three lantern tests. METHODS: The RLLT, FaLant, and OPTEC 900 were administered to 46 color vision-normal and 37 color vision-deficient (CVD) subjects. RESULTS: The pattern of errors on the RLLT was different from that of the FaLant and OPTEC 900. This may be accounted for, at least in part, by the different colors and the use of blank presentations in the RLLT. The three lanterns showed agreement in failing 21 and passing 6 of the CVD subjects (72.9%). The lanterns gave different results for 10 CVD subjects (27.9%): n = 5 passed only the RLLT and n = 3 passed only the FaLant; n = 1 failed only the FaLant and n = 1 failed only the RLLT. The overall failure rate by CVD for each lantern was 67.6% (RLLT), 73.0% (FaLant), and 78.4% (OPTEC 900). CONCLUSIONS: Despite the different construction principles, the pass/fail levels of the RLLT, FaLant, and OPTEC 900 are comparable and consistent with the performance of other lanterns listed by the CIE for Color Vision Standard 2. The RLLT may be a little easier to pass and is based on the signal color code used and actual signaling practice. We propose that the RLLT is also an appropriate lantern for CIE Color Vision Standard 2.

National standard for health assessment of rail safety workers: the first year.

OBJECTIVE: To determine the prevalence of health problems in New South Wales train drivers and the impact of the new national health-assessment standard on train drivers' fitness for work. DESIGN, SETTING AND PARTICIPANTS: Retrospective audit of files of all RailCorp train drivers (743) and train driver recruits (283) who were assessed under the new national standard for health assessment of rail safety workers between February 2004 and February 2005. MAIN OUTCOME MEASURES: Smoking status; prevalence of hypertension, heart disease, diabetes and obstructive sleep apnoea; alcohol use disorders; body mass index (BMI); total cholesterol level; fasting blood glucose level; cardiac risk score; fitness status. RESULTS: 25.2% of drivers and 27.9% of recruits were smokers; 43.8% of drivers and 21.9% of recruits were hypertensive; 34.6% of drivers and 31.4% of recruits had high total cholesterol levels (> 5.5 mmol/L). Median BMI values were 29 kg/m(2) (range, 18-59 kg/m(2)) for drivers and 28 kg/m(2) (range, 19-55 kg/m(2)) for recruits. The prevalence of obesity (BMI > or =30.0 kg/m(2)) was higher in both male drivers and recruits compared with the general male population. At initial assessment, 65.1% of drivers and 88.0% of recruits were certified as unconditionally fit for work; 12.4% of drivers and 7.1% of recruits were assessed as temporarily unfit; and 22.5% of drivers and 4.6% of recruits were considered fit subject to review (after periods ranging from 3 to 12 months). Two per cent of drivers and 2.5% of recruits were subsequently deemed to be permanently unfit, the most common reasons being heart conditions, psychiatric disorders, orthopaedic problems, colour vision impairment and sleep apnoea. CONCLUSIONS: Cardiovascular risk factors and cardiovascular disease are the most significant health issues affecting train drivers' fitness for work. With the more stringent health assessment and regular review required by the new standard, most drivers can continue with their duties, with the added benefits of improved personal health and greater safety to the rail network and the public.