Fatigue in patients with myasthenia gravis.

BACKGROUND: The subjective feeling of fatigue in myasthenia gravis (MG) is poorly elucidated, in part because it is often confounded with the objective sign of muscle fatigability. Another reason is the paucity of validated fatigue questionnaires in MG. METHODS: We applied the 9-item Fatigue Severity Scale (FSS) and the 40-item Fatigue Impact Scale (FIS) to 73 MG patients and 230 age- and sex-matched control subjects. We ascertained levels of education, marital status, and comorbidities such as depression, sleepiness, sleep times and sleep debt. Disease severity was graded according to the Myasthenia Gravis Foundation of America (MGFA) classification. RESULTS: All fatigue scores, with the exception of the cognitive FIS subscale, were higher in MG patients than controls. In MG, the prevalence of fatigue (defined by FSS scores ≥ 4.0) was 70%. Multiple regression analyses revealed several independent associates of fatigue, including depression (all fatigue scales), MGFA stage (FSS, physical FIS), female sex (cognitive and psychosocial FIS), and sleep debt (physical FIS). CONCLUSION: Fatigue in MG is highly prevalent, mainly physical, and influenced by depressive symptoms, disease severity, female sex and sleep debt. Cognitive fatigue in MG may not be a direct disease manifestation, but secondary to depression. The FSS and FIS represent reliable and validated tools, appropriate to discern meaningful clinical aspects of fatigue in MG. Clinical recognition of the complexity of fatigue may foster individualized treatment approaches for affected MG patients.

Temporal variation in prevalence and abundance of metacercariae in the pulmonate snail Lymnaea stagnalis in Chany Lake, West Siberia, Russia: long-term patterns and environmental covariates.

Infrapopulations of trematode metacercariae were monitored in the snail Lymnaea stagnalis over 17 yr (1982-1999) at Chany Lake, Novosibirskaya Oblast', Russia. Eighteen trematode species were recorded. Patterns of occurrence varied from 4 species (Echinoparyphium aconiatum, Echinoparyphium recurvatum, Moliniella anceps, and Cotylurus cornutus) that persisted at relatively high prevalence (> 60% of samples) across sites, seasons, and years, to species that were very rare and sporadic in occurrence. The stability of the 4 common species was probably because of their occurrence either in a wide range of definitive hosts or in a host adapted to the extreme abiotic changes that occurred from year to year in these wetlands. The prevalence and mean abundance of C. cornutus were negatively correlated with water level in the wetlands; its prevalence was also correlated with water temperature. The mean abundance of M. anceps was positively correlated with water level. The most probable explanation for the cyclic dynamics of infections of the common species is change in population sizes and densities of definitive and intermediate hosts, which mediated cyclic alterations in water levels.