Fatigue in ankylosing spondylitis--why is it ignored?

Fatigue in ankylosing spondylitis (AS) is largely ignored by physicians and classical texts. By contrast, patients frequently allude to it as a major complaint.

To address the situation, 3 studies were performed: (1) Symptoms were defined in a cross sectional evaluation of 1950 consecutive patients with AS. (2) From each of the 3 groups who specified a particular main symptom (pain, stiffness or fatigue), a random cohort of 20 was selected and all 60 were prospectively followed over a 14-day period. (3) An additional 100 patients [50 randomly selected with AS and 50 with rheumatoid arthritis (RA)] took part in a comparative prospective study.

In the first study for those with a definitive major symptom, 34% (n = 670) described pain while stiffness and fatigue were reported by 25% (n = 492) and 6% (n = 124), respectively. Thirty-two percent (n = 616) could not distinguish between the 3. Strikingly, when prospectively studied over a 2-week period, over 50% of the patients revealed that fatigue was the main symptom. Moreover, in the cohort which expressed pain as their major problem initially, fatigue had the highest prevalence (mean fatigue value versus mean stiffness, p = 0.009; fatigue versus pain, p < 0.001). In the direct comparison between patients with RA and those with AS, the RA cohort had statistically more fatigue and pain than the AS cohort (p = 0.002, p = 0.007, respectively) with a similar amount of stiffness expressed by both groups (n = 0.149). In both subsets, pain had the least impact on the patients (mean 2.60 and 1.87, respectively).

Our data reveal that fatigue should be considered a major problem for patients with AS, worthy of further exploration in terms of both etiology and therapy.