AbstractsBiology & Animal Science

Rheumatic diseases are characterized by inflammation, damage and pain, mostly of the joints and connective tissues. They can have a profound negative impact on almost every aspect of a patient’s life as well as on the direct environment and society as a whole. Patients are hampered in their daily activities by pain, physical disability,and fatigue,and also psychological distress is more prevalent than in the general population. A patient’s health is determined by a complex interplay between physiological and psychological factors. Research, especially prospective research taking account of between-subject differences and within-subject changes, is needed to clarify and verify the nature of these dynamic relations between physiological and psychological processes in rheumatic diseases. This thesis provides such research examining the prevalence of fatigue, psychological distress and physical disability and their possible association and dynamic interplay with inflammatory disease activity and deviant hormonal levels in four longitudinal and two cross-sectional studies of large patient samples. This thesis shows that compared to two decades ago, patients with rheumatoid arthritis nowadays are less physically disabled and psychologically distressed. The reduction in disease activity is indicated to have contributed to this improvement. Likely, the changed patient education also aided by emphasizing the importance of physical activity and living a valued life. However, while the mean burden of rheumatic disease has been alleviated over the past decades, the individual burden can still be substantial. Especially, severe fatigue, comparable to a level of fatigue in chronic fatigue syndrome, is shown to be widespread in 30 rheumatic diseases. Overall, one out of two patients is severely fatigued which emphasizes that fatigue should be a top priority in research and clinical practice. This thesis illustrates the complexity and elusiveness of the relationship of physiological processes with fatigue and psychological distress. First, low levels of the vitalizing hormone dehydroepiandrosterone sulphate are found not to be an explanation for high fatigue in patients with systemic lupus erythematosus. Moreover, fatigue in patients with rheumatoid arthritis is shown to be a rather stable individual characteristic that is not related to overall levels and changes in inflammatory disease activity, which suggests that treatment directed at disease remission is hardly a means to treat fatigue. Furthermore, this thesis indicates that a high psychological burden does not seem to interfere with anti-inflammatory treatment and might even benefit from it. Lastly, although often assumed, high psychological distress does not seem to worsen disease activity while disease activity does seem to be able to worsen psychological distress.