HSE Health & Safety Executive Co-ordinated investigation into the possible long term health effects of diving at work Examination of the long term health impact of diving: The ELTHI diving study Prepared by University of Aberdeen for the Health and Safety Executive 2004 RESEARCH REPORT 230 HSE Health & Safety Executive Co-ordinated investigation into the possible long term health effects of diving at work Examination of the long term health impact of diving: The ELTHI diving study Jennie I Macdiarmid PhD, John A S Ross MB ChB PhD FRCA, Claire L Taylor PhD, Stephen J Watt MBBS FRCPEd AFOM, Wendy Adie BSc Department of Environmental & Occupational medicine Liesl M Osman MA PhD Department of Medicine and Therapeutics David Godden MD FRCP (Glasg) FRCP (Edin) Highland & Island Health Research Institute Alison D Murray FRCR FRCP Department of Radiology John R Crawford PhD FBPsS CClinPsychol Department of Psychology Andrew Lawson MA MSc MPhil PhD CStat Department of Mathematics (now at Arnold School of Public Health, University of South Carolina) University of Aberdeen, Aberdeen, AB25 2ZP Scotland, UK We explored self-reported health and health related quality of life in a large group of divers (n=1540 56% response) compared to a non-diving group of offshore industrial workers (n=1035 51% response) with a questionnaire survey. We then validated the questionnaire responses by a detailed clinic assessment of a 10% random sample from each group. This included a range of objective tests and measurements. Finally, we studied reported ‘forgetfulness or loss of concentration’ in a case-control study, to determine the significance of this symptom and its relationship with diving practice. Health related quality of life (HRQOL) was similar in each group and within normative values. The major work related factor affecting HRQOL was industrial accident and this effect was most marked for offshore workers. A significant group of divers (18%) complained of ‘forgetfulness or loss of concentration’ and this was related to their diving experience. This complaint was associated with a significant moderate reduction in group mean HRQOL. A random sample of this group had a lower group mean performance on objective tests of cognitive function most particularly of memory and structural differences from control on cerebral MRI were associated with this group. The practice of welding had an unexpected amplifying effect in terms of the symptoms experienced by divers. There was a very high prevalence (50%) of objectively determined hearing disorder in both divers and offshore workers. This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy. HSE BOOKS © Crown copyright 2004 First published 2004 ISBN 0 7176 2848 5 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the copyright owner. Applications for reproduction should be made in writing to: Licensing Division, Her Majesty's Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by e-mail to [email protected] ii Acknowledgements The authors of this report would like to thank the all members of the ELTHI diving study for their invaluable contribution to this project. In particular we would like to thank Anne Henderson and Leanne Dow (project secretaries), George Henderson (technician), Drs Wendy Dollery and Ruth Stephenson (Consultants in Hyperbaric Medicine), and the staff at the University of Aberdeen MRI Research Unit and at the National Hyperbaric Centre. The authors would like to acknowledge the work of the Small Area Health Statistics Unit, Imperial College, London in determining Carstairs scores, Dr William J. Gunnyeon (Director of Health Services, AON Health Solutions) for collaborating in the study, Dr Finlay Dick (Senior Clinical Lecturer in Occupational Medicine) for assessment of the audiometric data and Dr Gordon Waiter (MRI Physicist Research Fellow) for performing MRI Volumetric Analysis. iii iv EXECUTIVE SUMMARY Diving and hyperbaric exposure is associated with a number of well recognised acute illnesses or injuries, including decompression illness (DCI), gas embolism and barotrauma. Recovery depends on the severity and nature of the diving incident, but in many cases it is complete. What remains less certain, however, are the possible long term health effects of diving, particularly in the absence of an injury. Dysbaric osteonecrosis has been associated with diving and is now a notifiable industrial disease in divers. Other aspects of health, however, have raised concern in divers but have not been conclusively associated with a career in diving, with any impact on quality of life or with a disease state. These include neurological abnormalities, lung function changes and inner ear damage. The aim of the ELTHI diving study (Examination of Long Term Health Impact of diving) was to investigate the possible long term health effects of diving at work. Furthermore, the significance of health complaints was assessed in terms of health related quality of life, as well as by reference to population norms. Methods Divers selected for this study had gained a professional diving certificate before 1991, issued by HSE. The comparison group consisted of age matched Oil and Gas industry offshore workers, who had undergone a medical to work offshore between 1990 and 1992, and had never dived. Neither divers nor offshore workers were required to be working as a diver or offshore, respectively, at the time of the study, but they were required to have been working in their respective industry at least 10 years prior to the study. This minimum time period was set to allow symptoms or medical conditions related to their career to become apparent. The study consisted of two parts, a postal questionnaire survey followed up with a detailed physiological and neuropsychological investigation (clinic study) of a sub-sample of the population who responded to the postal questionnaire survey. Part 1 –Questionnaire Survey (phase 1a): The questionnaire was sent by post to 2958 divers and 2708 offshore workers. Non-responders were sent the questionnaire a maximum of three times. The questionnaire was designed to assess occupational history, general health complaints, diagnosed medical conditions and health related quality of life (HRQOL). Part 2 – Clinic study: 10% random sample (phase 1b): this phase of the study consisted a 10% age stratified random sample of divers (n=151) and offshore workers (n=103) who had completed the questionnaire survey. The purpose of this phase was to check the reliability of the postal questionnaire and to identify asymptomatic hearing or neuropsychological deficits that would not have been detected in the postal questionnaire. Case-control study (phase 2): the largest effect observed between divers and offshore workers was for the complaint of ‘forgetfulness or loss of concentration’, with three times more divers than offshore workers reporting this complaint. Cases therefore comprised ‘forgetful’ divers (F divers) (n=102) while controls were ‘non-forgetful’ divers (NF divers) (n=100) and ‘non forgetful’ offshore workers (NF OSW) (n=100). Subjects in either section of the clinic study completed the following tests: subjective and objective measures of neuropsychological function, lung function, hearing, balance, a medical examination and detailed occupational history (including diving experience and accidents). In addition to these tests, subjects in the case-control study had MRI of the brain. v Results Postal Questionnaire survey The questionnaire survey had a response rate of 56% in divers and 51% in offshore workers. From the returned questionnaires 1540 divers and 1035 offshore workers met the inclusion criteria for the study. Divers were less likely than offshore workers to binge drink frequently, to be current smokers and to have gained higher educational qualifications. Divers were, however, more likely to have had a 3-day lost time accident at work, suffered a head injury and have worked as a welder. Adjusting analysis for lifestyle factors related to health, divers were more likely than offshore workers to report symptoms of ‘forgetfulness or loss of concentration’, ‘joint pain or muscle stiffness’ and ‘impaired hearing’. Divers were less likely than offshore workers to report skin complaints (itch or rash). Complaints of ‘forgetfulness or loss of concentration’ and ‘joint pain or muscle stiffness’ were associated with a significantly lower HRQOL scores. The reduction in HRQOL for those complaining of impaired hearing was less marked. The greatest difference between the groups was observed for ‘forgetfulness or loss of concentration’, which was three times more common in divers (18%) than offshore workers (6%). Work related accidents and work as a welder were found to be associated with health complaints occurring more commonly in divers. Adjusting for these factors removed differences between the groups for complaints of ‘joint pain and muscle stiffness’ and ‘impaired hearing’ but did not do so for ‘forgetfulness or loss of concentration’. In divers, after accidents and welding were allowed for, ‘joint pain and muscle stiffness’ was related to the amount of surface demand