The association between chronic diseases and fatigue in the working population Pascal M.L. Franssen, Ute Bu ¨ltmann, IJmert Kant, Ludovic G.P.M. van Amelsvoort* Department of Epidemiology, Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands Received 10 October 2001; accepted 25 February 2002 Abstract Objective: The aims of this study were to examine (a) whether employees with a chronic disease report more fatigue than employees without a chronic disease, (b) whether number or type of chronic disease is related to fatigue, and (c) whether differences in fatigue level in various types of chronic diseases are related to psychological distress. Methods: Data were taken from 12,137 employees. Fatigue was measured with the Checklist Individual Strength (CIS). Results: Employees with a chronic disease reported more fatigue (OR = 2.9, 95% CI = 2.7 – 3.2). Small differences were observed in the level of fatigue in various types of diseases. A strong linear association between the number of chronic diseases and fatigue was found. Psychological distress explained the higher level of fatigue in some chronic diseases (gastrointestinal diseases and migraine). Conclusions: Fatigue is more common in employees with a chronic disease. A strong association between number of chronic diseases and fatigue exists. Fatigue in employees with a chronic disease can partly be explained by psychological distress. Some chronic diseases show a stronger association between psychological distress and fatigue. D 2003 Elsevier Science Inc. All rights reserved. Keywords: Chronic disease; Epidemiology; Fatigue; Psychological distress; Working population Introduction Fatigue is best viewed as a subjective, continuous sen- sation with physical, psychological, behavioral, and cogni- tive components [1,2]. Symptoms of fatigue are commonly reported in the general population. Depending on the defini- tion and the method used to quantify fatigue, the prevalence may vary between 7% and 45% [2–4]. In the Maastricht Cohort Study of ‘‘Fatigue at Work,’’ which was established in 1998, we reported a prevalence of fatigued cases of 22% in a working population [5]. Different classifications of fatigue have been described. One of the most commonly used classifications differen- tiates between acute and chronic fatigue. Acute fatigue is seen as temporary and occurs as a consequence of physical or mental exertion [6]. Acute fatigue is self-limited and is relieved by appropriate rest. Chronic fatigue, in contrast, is not related to exertion, is poorly relieved by rest, lasts longer than 6 months, and often accompanies a chronic disease [6,7]. As a complaint, fatigue is separated in a primary complaint or it can be secondary to a known disease [8]. Even if fatigue occurs as a primary complaint, it might still be due to an unknown, underlying disease. Secondary to a disease, it has been described to accompany diseases like asthma [9], rheumatoid arthritis, cancer, diabetes, thyroid disease, multiple sclerosis [10], occult cancer, infectious mononucleosis, hepatitis, or chronic renal failure [2,3]. Fatigue in chronic diseases has been classified into central and peripheral fatigue, of which central fatigue appears to be the most relevant [7]. Different theories have been proposed to explain central fatigue in chronic diseases but all these theories involved the inhibition of corticotropin-releasing hormone, which has been linked to a higher level of fatigue [7,11,12]. Peripheral fatigue has been related to neuromus- cular dysfunction outside the central nervous system. For example, congestive heart failure leads to a decreased supply of oxygen into the muscles and thus to fatigue. In the same way, fatigue in chronic obstructive pulmonary disease (COPD) and anemia can be explained [13]. For most of the other chronic diseases, laboratory tests have not yet revealed a satisfactory biological etiology for fatigue 0022-3999/03/$ – see front matter D 2003 Elsevier Science Inc. All rights reserved. doi:10.1016/S0022-3999(02)00395-1 * Corresponding author. Tel.: +31-43-388-2363; fax: +31-43-388-4128. E-mail address: lgpm.vanamelsvoort@epid.unimaas.nl (L.G.P. van Amelsvoort). Journal of Psychosomatic Research 54 (2003) 339 – 344