In this study, comparison of children with FMF and their healthy peers for the sleep quality and fatigue levels revealed that sleep disturbance was significantly more common and fatigue levels were higher in the patient cohort. In the patient cohort, in high correlation with the disease severity, sleep quality decreased and fatigue levels increased significantly,. To the best of our knowledge, this study was conducted in the largest group of pediatric FMF cohort in the literature, comparing sleep problems and fatigue together with healthy children.
Previous reports on chronic rheumatic and autoinflammatory diseases has revealed that the health-related QoL of FMF patients may be affected negatively by sleep and mood disorders [2, 20, 21]. In 2014, a study by Makay et al. evaluated sleep problems in children with FMF for the first time [5]. They assessed sleep disturbance by utilizing The Children’s Sleep Habits Questionnaire (CSHQ) as an instrument. As per the information gleaned from this survey, elevated scores on the questionnaire correspond to a higher frequency of sleep disturbances. The findings in the report unveiled that, despite comparable sleep durations between patients with FMF and the control group, the total sleep scores for the patient cohort were markedly higher than those of the control group. Significantly, higher scores were present in terms of sleep delay, sleep anxiety, night awakenings and sleep-disordered breathing compared to healthy controls. A positive correlation was present between the number of attacks per year and delay in falling asleep, night awakenings and sleep-disordered breathing [5]. Consistent with this study, our study showed that sleep problems are more common in FMF patients, with higher PSQI scores. Besides, sleep problems worsen with increased fatigue, disease severity and number of attacks during the disease course. In another study, Küçükşahin and colleagues evaluated the relationship between sleep quality and fatigue, depression, anxiety, and disease activity in adults with FMF [21]. Their findings indicated that patients with FMF reported notably elevated scores in depression, anxiety, fatigue, and PSQI compared to the healthy control group. Their research also demonstrated a connection between poor sleep quality and levels of inflammatory markers during attacks, as well as associations with fatigue and the frequency of attacks over the last three months. In line with our study, they observed that as the severity of the disease heightened, both total PSQI scores and scores within its specific domains increased.
Presence of sleep disorders can lead to behavioral problems and depression in all populations. Depression, which is a common comorbidity in FMF and chronic diseases, has been associated with both fatigue and sleep disturbance and/or deficit. In the study conducted by Fredriksen et al. in 2004 on 2259 adolescents [22], it was aimed to track the effects of sleep loss in adolescents during their middle school years. Children who slept less and had sleep problems had more frequent mood and anxiety disorders. Those students who experienced reduced sleep duration in their sixth-grade year displayed lower initial self-esteem and academic grades, alongside elevated initial levels of depressive symptoms. Likewise, students with a consistent pattern of insufficient sleep reported an increase in depressive symptoms and a decline in self-esteem over time. In the study by Hysing et al., the relationship between sleep and emotional and behavioral problems in chronic diseases was investigated. It was found that patients with chronic diseases were more likely to be delayed in falling asleep and woke up at night more frequently than healthy individuals, and emotional and behavioral disorders were more common in children with chronic diseases [20]. Sleep problems should be evaluated periodically in chronic diseases such as FMF, and recovery should be achieved by controlling the disease.
Fatigue is a common and complex phenomenon and remains a significant health problem in chronic inflammatory rheumatic diseases of both adults and children such as FMF, rheumatoid arthritis, psoriatic arthritis, or systemic lupus erythematosus. Since it directly is associated with poor QoL, it can negatively affect compliance with medications and indirectly the control of the disease [23]. In 2016, Nijhof and colleagues conducted a study to ascertain the prevalence of severe fatigue and its associated limitations among adolescents grappling with pediatric rheumatic diseases. Their findings revealed that 25% of the patients in this cohort experienced severe fatigue. The study concluded that individuals with fatigue demonstrated notably lower levels of physical functioning and a higher incidence of school absenteeism compared to those without fatigue [24]. In a similar study by Özdel et al., which included 111 patients with FMF, 54 patients with other chronic rheumatic diseases, and 79 healthy individuals, fatigue levels were compared by Checklist Individual Strength-20. While similar scores were found between FMF patients and patients with other chronic rheumatic diseases, fatigue levels were significantly higher in both groups compared to healthy individuals [12]. In line with these reports, our study revealed that disease-related factors such as disease severity and the number of attacks were also correlated with fatigue levels and less fatigue was observed in well-controlled patients. Furthermore, a negative correlation was present between age and the the general fatigue and sleep/rest related fatigue scores in PedsQL-MFS score. Fatigue level was higher and sleep quality was poorer in the adolescent age group.
In the study conducted by Duruöz et al. in 2017, using 4 different fatigue scales in adult patients with FMF, compared to control group, patients had increased pain, fatigue, sleep disturbance and decreased QoL. It was speculated that fatigue levels may be related to disease severity, disease duration and attack frequency [14]. Our results similarly revealed that disease control may have a positive influence on fatigue levels in pediatric patients with FMF.
In 2001, Ben-Cherit and colleagues linked menstrual FMF attacks to the decrease in estrogen during menstruation [25, 26]. Although we did not perform an analysis regarding menstruation and disease activity in our study, there was no significant difference in PedsQL-MFS scores between the male and female patient groups. However, general fatigue levels in girls was significantly worse than in boys. It is possible that this result can be attributed to high emotional stress in girls and the presence of menstrual bleeding, but further randomized controlled studies on the pathophysiology of this subject are needed.
A recent study assessing the psychometric properties of PedsQL-MFS in 71 children with FMF found no discernible differences in PedsQL-MFS scores between groups, regardless of colchicine use or the presence of the M694V mutation (p > 0.05) [27]. In our study, no significant difference was present between patients carrying homozygous, heterozygous, or compound MEFV gene mutation in terms of sleep quality and fatigue levels.
This study has some potential limitations. The lack of analysis regarding compliance with medications and level of physical activity that may affect sleep quality limited the multifaceted evaluations. It would also be possible to evaluate sleep with polysomnography, an objective method. Since this is a cross-sectional study, longitudinal studies can better reveal the relationship between disease activity and fatigue level and sleep quality. However, the presence of a control group, the large size of the patient cohort, and the prospective analysis using validated scales make this study superior to previous ones.
In conclusion, this study contributes to the literature by highlighting the clinical significance of assessing and managing sleep problems, as well as fatigue levels, in children with FMF. This approach, which aims to enhance the QoL of patients, should be incorporated into routine visits.