The overall aim of this thesis was to gain knowledge about experiences of fatigue among individuals diagnosed with MS and to compare these experiences with those of individuals in the general population. Individuals' experiences of fatigue have been approached both inductively and deductively and qualitative and quantitative research methods have been combined. A total of 372 individuals participated in the studies: 178 individuals diagnosed with MS (I-IV), and 194 individuals randomly selected from the general population. These individuals functioned as reference group and were comparable with the MS sufferers as regards age and sex (III-IV).

Experiences of fatigue were investigated before-and-after an intervention with a cooling suit among eight individuals diagnosed with MS (I). Fatigue as lived through and its perceived meaning were addressed in a phenomenological interview study among nine individuals with MS (II). Reliability and validity of a tool to assess impact of fatigue in daily life, the Swedish version of the Fatigue Impact Scale (FIS), was investigated in a cross-sectional study among 161 individuals with MS in comparison with 194 individuals in the general population (III). Further, experiences of fatigue, in terms of its perceived impact in daily life in relation to perceived health was addressed in a study which comprised 155 individuals diagnosed with MS who were compared with 190 individuals from the general population (IV).

The collection of data included open interviews conducted before-and-after the intervention (I) and in the phenomenological study (II). A self-written semi-structured oneweek diary was completed during the test-period with the cooling suit (I). Perceived impact of fatigue in daily life was assessed in a self-assessment questionnaire, with the FIS (I, III, IV) and a symptom list (IV) included. The individuals' perceived health was addressed by means of a single rating-question (IV).

Living with fatigue means living with a time-consuming and an all-absorbing phenomenon, which is both non-constructively and constructively perceived and involves either the whole body or parts of it (II). Experiences of fatigue were reduced during the intervention period. Overall levels of fatigue, in terms of its duration and perceived severity, and also its perceived impact in daily life, were reported diminished and the participants reported a sense of well-being and contentment during the period (I). Among the individuals with MS, fatigue was regarded as one of, or as their worst symptom. The experience of fatigue was more than three times as frequent as among the individuals in the general population. In MS, the perceived impact of fatigue in daily life was not found to be related either to age or numbers of years of being diagnosed with MS, but it was with the indicated levels of perceived health (IV). Among individuals diagnosed with MS, the FIS was found to be a reliable and valid tool measuring impact of fatigue in daily life. Also in the reference group comprising individuals in the general population, the FIS captured and distinguished between different levels of the impact of fatigue (III).