3.1 Correlations between demographic, clinical, and psychological characteristics and total fatigue
As shown in Table 1, Table 2, Results indicated that 96.3% gout participants were male, the media (IQR) age of the gout respondents was 54 (38,64) years, a mean ± standard deviation of BMI was 25.37 ± 3.48, 58.3% come from urban, 60.2% of the patient’s educational level no more than 9 years, and more than one-third of the patients’ yearly per capita family income was less than 15000 RMB. In addition, more than half of participants have tophi (51%) and comorbidities (52.4%), it suggests a severe disease burden. Among the gout participants, more than half of gout patients(64.9%) are in the acute stage, the median (IQR) of disease duration were 5 (2,12) years and laboratory indexes include ESR, CRP, sUA were 15 (6, 35.25) mm/h, 13.65 (4.83, 33.65) mg/l, and 473.62 ± 124.36μmol/L, respectively. According to the cut-off scores, depression disorder was presented in 12.9%, 6.1% had anxiety. Not only that, we found 199 (48.5%) gout patients have sleep disorders. Spearman rank correlation coefficients were computed to identify the relationships among two dimensions of FS-14, demographic, clinical, and psychogenic variables in present sample of gout patients. Patients with live in urban, low level of education, have no job, longer disease duration and hospitalization, severe total pain, have tophi, comorbidity, higher degree of depression and anxiety, have sleep disorder, higher level of ESR and CRP were more likely to have higher scores of fatigue(P<0.05).
3.2 Differences between psychological, clinical characteristics and quality of life of gout patients grouped by each item of FS-14
Figure S1 [Additional file 1] presented the proportion of each fatigue item in FS-14, we found that in physical fatigue Question (Q1-8), the proportion of each fatigue item more than 50% and patients with physical fatigue showed higher degree of anxiety, higher degree of depression, worse sleep quality, more severe pain (P<0.05), lower quality of life: PCS (P<0.001), MCS (P<0.001). Except Q1, gout patients with fatigue showed more serious functional disability (P<0.05). Comparing patients without fatigue, except Q1 and Q3, patients with fatigue had increased disease activity.
In addition, we compared patients with and without mental fatigue (Q9-14). In Q9, gout patients with fatigue showed higher degree of anxiety (P<0.001), higher degree of depression (P<0.001), worse sleep quality (P<0.001), more severe pain (P=0.015), more serious functional disability (P=0.001). In Q11, gout patients with fatigue showed worse sleep quality (P=0.038), more serious functional disability (P=0.041). In Q12, gout patients with fatigue showed higher degree of anxiety (P=0.002), higher degree of depression (P=0.007). In Q13, gout patients with fatigue showed higher degree of depression (P=0.026). In Q14, gout patients with fatigue showed higher degree of anxiety (P=0.012), higher degree of depression (P=0.001). Patients with mental fatigue had lower quality of life in MCS (P<0.05). The results are shown in Table S1 [Additional file 2].
3.3 Differences between demographic, psychological, clinical characteristics and quality of life of gout patients in single item subjective report fatigue of FS-14
In Q1: Do you have problems with tiredness? According to patients choose “yes” or “no”, the comparison in demographic, psychological, clinical characteristics and quality of life were exhibited in Table S2,3 [Additional file 3,4], gout patients with fatigue showed higher degree of anxiety, higher degree of depression, worse sleep quality, more severe pain, the occurrence of fatigue significantly reduces the quality of life in gout patients both physically and psychologically.
3.4 Determinants of Fatigue in gout patients
Stepwise multiple linear regression analysis was conducted to investigate contributors of fatigue in Table 3. Depression (r=0.366, P<0.001) and pain (r=0.237, P=0.005) were significantly accounted for fatigue.
Stepwise logistic regression analyses were used to identify a model to predict gout patients who would have tiredness problem in single item. The results indicated that anxiety (OR=9.848) and sleep quality (OR=2.397) were significant risk factors for fatigue in gout patients (Table 4).
3.5 Correlations between Quality of life and fatigue in gout patient
Correlations among quality of life and fatigue in gout patients was summarized in Table 5. We found that fatigue have a significant negatively correlated with each component of SF-36 by Spearman rank correlation analysis (P<0.05).
3.6 Fatigue lower the quality of life in gout patients
Total fatigue scores in gout patients were divided into four subgroups, G1 (P0-P25), G2 (P25-P50), G3 (P50-P75), G4 (P75-P100), corresponding to 0-3 points, 4-5 points, 6-8 points, 9-14 points, respectively. The rank-sum test was used to analyze the difference of life quality in gout patients with different fatigue degrees. In conclusion, we found that patients with higher fatigue scores had significantly lower HR-QoL in all domains of the SF-36 scale. Table 6 and Figure S2 [Additional file 5] presented that the more severe the fatigue, the lower the patient’s HR-QoL.