Sleepiness or fatigue? Can we detect treatable causes of tiredness in primary Sjögren's syndrome?

OBJECTIVE: To study the prevalence of fatigue and daytime sleepiness in primary SS (pSS) and analyse predicting sleep disturbing factors and other potential determinants of fatigue and sleepiness.
METHOD: Seventy-two consecutive pSS patients and 59 age-matched healthy controls were compared. Assessment instruments were profile of fatigue (ProF), visual analogue scale fatigue, Epworth Sleepiness Scale (ESS), Hospital Anxiety and Depression Scale, restless legs syndrome (RLS) Diagnostic Criteria and Lund University Sleep Questionnaire. In addition, markers of immune disturbance, inflammation and disease activity using the European League Against Rheumatism SS Disease Activity Index were analysed in patients.
RESULTS: Fatigue, especially somatic fatigue, is the main problem for pSS patients. Sleepiness is a minor problem. Patients had significantly more often anxiety, nocturia and woke up more frequently during the night than controls. The factors that predicted daytime fatigue in pSS patients were anxiety and nightly awakenings due to pain. Nocturia was frequent but was not associated with fatigue or sleepiness. RLS, depression and sicca symptoms contributed to fatigue in the univariate regression analysis only.
CONCLUSIONS: This is the first study demonstrating not only the presence of disturbed sleep, but also that nightly musculoskeletal pain and other sleep disturbing factors and anxiety significantly influence fatigue. Management strategies aimed at these aspects should therefore be included in future trials for treatment of fatigue in pSS.