Fatigue in the Danish general population. Influence of sociodemographic factors and disease

Objective-To measure the levels of fatigue in the general population, and t o examine how disease and sociodemographic factors influence fatigue. Design-Cross sectional questionnaire study in the Danish general population . Subjects-A random, age stratified sample of 1608 people aged 20-77 with a n equal gender distribution (response rate 67%). Main outcome measures-Five fatigue scales from the questionnaire Multidimen sional Fatigue Inventory: General Fatigue, Physical Fatigue, Reduced Activi ty, Reduced Motivation and Mental Fatigue. Results-Fatigue scores were skewed towards absence of fatigue. The General Fatigue and Physical Fatigue scales showed the highest fatigue levels while the Reduced Motivation scale showed lowest levels. Gender differences in f atigue scores were small, but the variability among women was higher-that i s, more women had high scores. A multiple linear regression analysis showed that respondents of low social status and respondents with a depression ha d high fatigue scores on all scales, independent of other factors. Chronic somatic disease had an independent direct effect on Mental Fatigue, but for the rest of the scales, the effect of somatic disease depended on age, gen der and/or whether the person was living alone. For example, General and Ph ysical Fatigue decreased with age among healthy people, whereas scores on t hese scales increased with age among those with a somatic disease. Conclusions-Physical and mental diseases play essential parts for the level of fatigue and as modulators of the associations between sociodemographic factors and fatigue. These interactions should be taken into account in fut ure research on fatigue and sociodemographic factors and when data from cli nical studies are compared with normative data from the general population.