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Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus (1) and has placed extraordinary demands upon health care systems worldwide. Unlike previous public health challenges, health care workers (HCWs) comprised a high proportion of the nearly 8000 infected persons across 29 countries: the percentage of infected HCWs ranged from 3% in the US, where most cases originated from international air travel (2), to as high as 22% in Hong Kong (3), 33% in Taiwan (4), and 51% in Toronto (5), with a mortality rate of 15% (6). Since early SARS resembles influenza (7), widespread avoidance of crowded places occurred in Hong Kong. HCWs were rapidly deployed to SARS wards. A qualitative study of 11 HCWs in Toronto found HCWs were concerned about infecting others, about stigma, and about social isolation (8). The scale of consequent psychological problems for this group has not been formally evaluated, but they can undermine health and clinical performance (9). MethodThe study was approved by the hospital Institutional Review Board. We employed a self-administered questionnaire which contained the Perceived Stress Scale (PSS-10; 10) to determine stress levels over 1 month, together with a structured list of putative psychological effects of SARS, compiled after team discussion and consensus (available on request). Pilot work on 120 subjects showed that the questionnaire was completed independently and quickly by 88% of staff, which was of practical importance owing to work pressure. Power analysis (GraphPad Instat) (11) showed that 260 subjects per group had 90% power to detect a 10% difference at P < 0.01. A sample of 271 HCWs and 342 healthy control subjects provided informed consent and completed the questionnaire between 11 April and 19 May 2003. HCWs were recruited from SARS units of 2 major hospitals: one a teaching hospital and the other responsible for the Amoy Gardens apartments, which alone produced 329 confirmed SARS cases. We recruited healthy control subjects from members of the public who lacked health care experience and contact with SARS; these subjects were balanced for age, sex, and educational level of the HCWs. Questionnaires were quarantined for 24 hours before data entry. We analyzed group comparisons on nominal variables using the chi-square test, ordinal variables using Mann–Whitney tests, and interval variables using t tests. Bonferroni correction was made for multiple comparisons. Two-way analysis of variance (ANOVA) compared groups on the direction (negative vs positive) of psychological effects of SARS. Spearman’s rho computed correlations with the PSS. ResultsA successful response rate of 80% from both groups yielded 613 questionnaires with valid data. This comprised 271 questionnaires from HCWs and 342 from healthy control subjects. Groups were balanced for age (most [45% to 50%] were aged 19 to 30 years, followed by 31 to 40 years [25% to 33%]; Mann–Whitney U test, P = 0.10), sex (female-to-male ratio, 3:1; c2 = 2.2, P = 0.14), and education (tertiary level 60%; Mann–Whitney U test, P = 0.78). The 2 groups also had similar living circumstances (75% with family; c2 = 6.3, P = 0.1) and parenthood (30% had children; c2 = 1.0, P = 0.3). HCWs were mostly nurses (60%), ward assistants (17%), and doctors (12%); they worked in respiratory medicine (60%), internal medicine (15%), and deployed specialties (15%). Stress levels in the outbreak were 18.6 (SD 4.9) for HCWs and 18.3 (SD 5.6) for healthy control subjects; this represents approximately 50% more than the normative value of 13 (12). For meaningful comparison, published PSS-10 values for life events include unemployment (16.5), separation (16.6), or work disability (19.9) (12). Strikingly, HCWs were not more stressed than healthy control subjects (HCWs mean 18.6, control subjects mean 18.3; Mann–Whitney U, P > 0.9). We observed that PSS score and negative psychological effects from SARS were highly significantly correlated (Spearman’s rho = 0.4, P < 0.001). Of the sample, 80% affirmed that these effects were not attributable to other contemporaneous events. Briefly, we observed that HCWs appeared to be protected from stress, with significantly more positive psychological effects than were observed in control subjects (group by direction of response interaction F2,606, P = 0.025, 2-tailed). Such positive responses were reported by 94% (n = 256) of HCWs and included awareness of hygiene (85%), focus on current affairs (77%), unity (51%), and awareness of danger (41%). However, 89% of HCWs (n = 241) also experienced negative sequelae such as tiredness (71%), worry about health (59%), and fearing social contact (46%). HCWs who were confident about infection control (74%, n = 179) had lower stress levels (independent samples t test, 2-tailed, P = 0.001) and fewer negative effects (independent samples t test, 2-tailed, P = 0.004). Confidence about infection control was independent of education, perhaps because of 100% attendance at infection-control training. DiscussionThis study was conducted prospectively during an unprecedented public-health challenge. Stress was elevated in both groups but, importantly, was not relatively increased in HCWs. Given the risks faced by HCWs, this observation is unexpected. We chose the PSS-10 (10) because it is quick, reliable, self-administered, sensitive to nonoccurrence of events, validated in community samples, and not anchored to a single event. It measures the degree to which life situations are appraised as unpredictable, uncontrollable, and overloaded (12). We did not attempt to assess the psychometric properties of the questionnaire during the outbreak, but our preliminary observations suggest that positive responses to stress, as well as education, may protect HCWs. Finally, for healthy control subjects, elevated stress may mean that monitoring for psychiatric sequelae is desirable. While the threat of future outbreaks remains, formal psychometric validation of the questionnaire is planned at follow-up. AcknowledgementsWe thank Dr KF Chung for the Chinese version of PSS-10 and colleagues of Queen Mary and United Christian Hospitals for assistance. References1. Peiris JSM, Lai ST, Poon LLM, Guan Y, Yam LYC, Lim W, and others. Coronavirus as a possible cause of severe acute respiratory syndrome. Lancet 2003;361:1319-25. 2. Update: Severe acute respiratory syndrome–United States, May 21, 2003. JAMA 2003; 289:19:2495–6. 3. Latest figures on 2003 Severe Acute Respiratory Syndrome Outbreak. Hong Kong Government, SAR China, Department of Health. Available: http://www.info.gov.hk/info/sars/e_sars2003.htm. 4. Centers for Disease Control and Prevention. Severe acute respiratory syndrome – Taiwan, 2003. MMWR CDC Surveill Summ 2003;52:461–6. 5. Booth CM, Matukas LM, Tomlinson GA, Rachlis AR, Rose DB, Dwosh HA, and others. Clinical features and short-term outcomes of 144 patients with SARS in the Greater Toronto Area. JAMA 2003;289:1-9. Available: http://jama.ama- assn.org/cgi/reprint/289.21.JOC30885v1.pdf. 6. Clinical Trials Centre, The University of Hong Kong. Hong Kong SARS update. April to May 2003 [press release online]. Hospital Authority and Hong Kong SAR Government. Available: http://www.hku.hk/ctc/. 7. Tsang KW, Ho PL, Ooi GC, Yee WK, Wang T, Chan-Yeung M, and others. A cluster of cases of severe acute respiratory syndrome in Hong Kong. N Engl J Med 2003;348:1977-85. Available: http://content.nejm.org/cgi/reprint/ NEJMoa030666v1.pdf. 8. Maunder R, Hunter J, Vincent L, Bennett J, Peladeau N, Leszcz M, and others. The immediate psychological and occupational impact of the 2003 SARS outbreak in a teaching hospital. CMAJ 2003;168:1245–51. 9. Firth-Cozens J. Interventions to improve physicians’ well-being and patient care. Soc Sci Med 2001;52:215–22. 10. Cohen S, Kamarck T, Mermelstein R. A global measure of perceived stress. J Health Soc Behav 1983;24:385–96. 11. Motulsky H. Instat Version 2. San Diego (CA): GraphPad Software Inc; 1990–1994. Available: http://www.graphpad.com/. 12. Cohen S, Williamson G. Perceived stress in a probability sample of the United States. In: Spacapam S, Oskamp S, editors. The social psychology of health: Claremont Symposium on Applied Social Psychology. Newbury Park (CA): Sage; 1988. Author(s)Manuscript received September 2003, revised, and accepted November 2003. 1. Assistant Professor, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. 2. Research Assistant, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. 3. Medical Student, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. 4. Senior Medical Officer, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. 5. Head and Chair Professor, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. 6. Executive Manager, Professional Services, Hospital Authority, Argyle Road, Kowloon, Hong Kong, SAR China. 7. Senior Medical Officer, Department of Psychiatry, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong, SAR China. 8. Consultant Physician, Department of Medicine, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong, SAR China. 9. Associate Professor and Honorary Consultant Physician, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China. Address for correspondence: Dr SE Chua, Department of Psychiatry, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, SAR China e-mail: sechua@hkucc.hku.hk
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