Zhang, Wu, Liu, and Zhu: Prevalence of Depression in Ankylosing Spondylitis: A Systematic Review and Meta-Analysis

Abstract

The aim of this study was to provide a summary estimate of depression prevalence among people with ankylosing spondylitis (AS) in comparison to those without AS. A systematic literature search was conducted using PubMed, Embase, PsycINFO, Web of Science, the Cochrane database library, China National Knowledge Infrastructure, and Wanfang Database from their inception to December 2016. The results showed that thirty-one eligible studies involving 8,106 patients were analyzed. Fifteen methods of defining depression were reported. The overall pooled prevalence of depression was 35% (95% CI, 28–43%), with high between-study heterogeneity (I2=98.8%, p<0.001). The relative risk of depression among people with AS was 1.76 (95% CI: 1.21–2.55, eight studies, n=3,006) compared with people without AS. The depression score [standardized mean difference (SMD)=0.43, 95% CI: 0.19–0.67, seven studies, n=549] was higher in AS patients than in controls. The main influence on depression prevalence was the sample size and country of origin. In conclusion, one-third of people with AS experience symptoms of depression. Depression was more prevalent in AS patients than in controls. Further research is needed to identify effective strategies for preventing and treating depression among AS patients.

INTRODUCTION

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease with significant effects on patients’ physical function and psychological status [1,2]. It has become increasingly clear that psychological distress, such as depression or anxiety, is common in patients with including osteoarthritis [3], lupus [4] and rheumatic arthritis [5,6]. Individuals with AS are more likely to be depressed than healthy individuals [7]. Depression is a chronic, prevalent condition, and is a leading cause of disability, affecting at least 120 million people worldwide [8]. In a population based study, doctor-diagnosed depression was found to be increased 1.81 and 1.49 fold respectively in women and men with AS [9]. It may be explained that AS is related to inflammation of depression because it is an inflammatory disease. Depressed AS patients tended to have poor long-term outcomes, including increased disease activity [10,11], fatigue [12], decreased functionality [13], sleep disturbances [14], impaired quality of life [15], and high medical costs [16]. However, estimates of the prevalence of depression in AS patients varied across studies, from 3% [17] to 66% [18]. Such discrepancy could be explained by the differences in time frames when these studies were performed, study quality, or tools used for assessing depression. It is important for rheumatologists to establish reliable estimate of depression prevalence, in order to prevent, treat, and identify causes of depression in people with AS. Recent reviews have suggested that depression was highly prevalent among people with rheumatoid arthritis [19], osteoarthritis [3], and systemic lupus erythematosus [20]. Another systematic review found that the prevalence of neuropsychiatric damage in chronic rheumatic diseases such as lupus has been significantly increasing over the past 5 decades [21]. This finding is not surprising due to reduction in white matter and grey matter volumes in the very early stage of lupus [22]. As yet no systematic review has provided pooled prevalence estimates of depression in AS. Our goal was to fill this gap. We aimed to 1) describe the pooled prevalence of depression in people with AS; 2) compare depression prevalence and score in AS patients versus healthy controls; 3) explore the influence of study characteristics on prevalence estimates.

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standard [23] and followed a predetermined registered protocol (PROSPERO: 42016052590).

Search strategy

The systematic literature search was conducted by two investigators independently through the PubMed, Embase, PsycINFO, Web of Science, Cochrane database library, China National Knowledge Infrastructure (CNKI), and Wanfang Database for pertinent studies published in English or Chinese from their inception to December 2016. The computer-based searches combined terms related to AS patients [(depress* or depress* disorder$ or affective disorder$ or mood disorder$ or adjustment disorder$ or affective symptom$ or dysthymi*) AND (Ankylosing spondylitis or AS)] (Supplementary Material 1 in the online-only Data Supplement). The search was restricted to studies in humans. In addition, the reference lists of all identified relevant publications were reviewed. Finally, where published information was unclear or inadequate, we contacted the corresponding authors for more information.

Inclusion and exclusion criteria

Studies were eligible if they met the following criteria: 1) observational studies (cross-sectional and prospective studies) and baseline data of randomized controlled trials with or without a comparison group without AS; 2) depression was measured by self-reported symptom scales, physician/clinician diagnosis, or structured clinical diagnostic interview. Table 1 presented a full list of the eligible methods of detecting depression, alongside the numbers of participants assessed.
Studies were excluded if: 1) the study was not published as the full reports, such as case reports, commentaries, conference abstracts and letters to editors; 2) the study had a retrospective design; and 3) participants with depression at baseline were not excluded for the analysis.

Data extraction and quality assessment

Two trained investigators independently extracted data and assess quality of the studies included in this meta-analysis. Any disagreements in data extraction and quality assessment were resolved through discussion between the two investigators or adjudication with a third reviewer. We used a standardized form to record data on the authors, year of publication, country of study, participants, percentage of male participants, average age of participants, mean disease duration, criteria for detection of depression, and reported the prevalence or score of depression. If duplicate publications from the same study were identified, we would include the result with the largest number of individuals from the study. Wherever possible, we extracted the number affected and not affected by depression in each sample (using the authors’ cut-off points for each outcome measure). If this was not available, we extracted the mean and standard deviation of the depression assessment scale. The investigators independently fulfilled the quality assessment using a modified version of the Newcastle-Ottawa Scale (NOS) in line with previous study [24]. Studies were judged to be at low risk of bias (≥3 points) or high risk of bias (<3 points).

Outcome measures

The outcomes of interest were major depression diagnosed with a structured clinical assessment [e.g., International Classification of Diseases (ICD)-10] or depression assessed with a validated assessment tool or screening measure [e.g., the Hospital Anxiety and Depression Scale (HADS), Beck Depression Inventory (BDI)].

Statistical analyses

Three analyses were undertaken. First, we pooled studies reporting the prevalence of depression in the AS sample using a random-effects models [25,26]. Second, we used a pooled relative risk (RR) analysis with random-effect model. Third, we conducted a pooled standardized mean difference (SMD) analysis to investigate differences between those with and without AS. Statistical heterogeneity among studies was evaluated with I2 statistics with the values of 25%, 50%, and 75% respectively denoted cut-off points for low, moderate and high degrees of heterogeneity [27]. The influence of individual studies on the overall prevalence estimate was explored by serially excluding each study in a sensitivity analysis. Subgroup analyses were planned by overall study quality, sample size, country of origin and publication year to explore the sources of potential heterogeneity. Finally, we used Pearson’s and Spearman’s correlation analyses to assess the association between variables and prevalence of depression in people with AS. Potential publication bias was evaluated with a funnel plot [28] and the Egger’s test [29]. Statistical analyses were all conducted on Statistical analyses were all conducted on STATA version 12.0 (Stata Corp, College Station, TX, USA).

RESULTS

Search results

A total of 598 citations were identified. After removal of duplicates, titles and then abstracts were screened for potential eligibility. From this, 59 were potentially eligible and considered in the full-text review. Twenty-eight articles were excluded; thus, 31 records met the eligibility criteria and were included (Figure 1), and a full reference list was shown in Supplementary Material 2 (in the online-only Data Supplement). Inter-observer agreement (κ) between two investigators was 0.89.

Study characteristics

Table 1 and 2 presented the characteristics of the included studies. Thirty-one eligible studies consisted of 8,106 patients were reported. Nineteen studies were conducted in Asia, 7 studies in Europe, 3 studies in Africa, and 1 study in South America. The mean age was 39.2 years, and the mean percentage of males represented in the sample was 75.9%. In addition, the mean number of participants per study was 261, and the mean disease duration was 10.64 years. Table 3 described the methods defined depression and the frequency of their use. Depression was assessed in 15 different ways. Thirteen studies assessed for depression using the HADS; three different cut-off points were presented, the most commonly used being 8. Five studies assessed for depression using the 21 Item-BDI, with four different thresholds were presented in the articles. Six used the Zung Self-rating Depression Scale (SDS), and three used other screening tools. Three assessed for depression using structured interview (e.g., ICD). Supplementary Table 1 (in the online-only Data Supplement) summarized the quality assessment using a modified version of the NOS, which indicated that 1 study received 5 points, 3 studies received 4 points, 6 studies received 3 points, 18 studies received 2 points, and 3 studies received 1 point.

Prevalence of depression among AS patients

Prevalence estimates of depression varied from 3% to 66% in individual studies (Table 1). The overall pooled prevalence of depression was 35% (95% CI, 28–43%), with high betweenstudy heterogeneity (I2=98.8%, p<0.001) (Figure 2). Table 3 presented the summary of meta-analyses and heterogeneity assessments. Prevalence estimates ranged from 9% (95% CI, 6–12%, I2=29.6%) according to the Hospital Anxiety and Depression Scale with thresholds of 11% to 49% (95% CI, 34–60%, I2=0%) for the 21-Item Beck Depression Inventory with a cutoff of 14 or more. Prevalence of major depressive disorder to be 13% (95% CI, 6–20%) according to the structured interview, with high heterogeneity (I2=98.4%).

Depression in AS versus non-AS cohorts

Eight studies included data on the prevalence estimates of depression for people with AS compared with those without AS. A pooled RR of 1.76 (95% CI: 1.21–2.55, n=3006) (Figure 3). Seven studies (n=549) presented data comparing depression scores for people with AS compared with those without AS. The depression score (SMD=0.43, 95% CI: 0.19–0.67) was higher in AS patients than in controls (Figure 4).

Sensitivity and subgroup analyses

Table 4 showed the prevalence estimates of depression according to each sensitivity and subgroup analysis, in comparison with the primary analysis. Sensitivity analyses found that the exclusion of studies with less sample representativeness tended to decrease depression prevalence estimates according to structured interview. The pooled SMD tended to decrease in AS patients verse controls by exclusion of studies only using male sample. The subgroup analyses were conducted by sample size, overall quality, publication year, and country of origin. The results showed that studies with sample size <200 had higher depression prevalence estimates [52% (95% CI, 44–60%) vs. 42% (95% CI, 39–45%)] compared with primary analysis according to the HADS with thresholds of 8, and higher pooled RR [3.72 (95% CI, 1.33–10.38) vs. 1.48 (95% CI, 1.06–2.06)] in AS patients verse controls compared with the studies with sample size ≥200. When evaluated by Newcastle-Ottawa Scale (NOS), studies with lower total overall quality scores yielded higher depression estimates [52% (95% CI, 41–63%) vs. 45% (95% CI, 28–62%)] according to the HADS with thresholds of 8, and higher pooled RR [3.72 (95% CI, 1.33–10.38) vs. 1.48 (95% CI, 1.06–2.06)] compared with the studies with higher total overall quality scores. More recent publications and developing country tended to yield higher depression prevalence estimates according to the HADS with a cutoff of 8 or more. There was no particular trend or pattern in any other sensitivity analyses or subgroup analyses.

Associated study variables

Pearson’s and Spearman’s correlation analyses were employed to examine the relationship between variables including proportion of male participants, mean/medium age, mean/medium disease duration, sample size, representativeness, comparability, overall quality, country of origin, publication year, and the prevalence of depression. We found that small sample size (r=-0.45, p=0.016) and developing country (r=0.613, p=0.001) of the sample were significantly associated with increased depression prevalence (Table 5).

Assessment of publication bias

According to the Egger’s test, assessment of publication bias suggested significant publication bias in studies reporting depression [Egger: bias=7.87 (95% CI: 4.77–10.97), p<0.001] (Supplementary Figure 1 in the online-only Data Supplement).

DISCUSSION

This is the first systematic review and meta-analysis on the prevalence of depression in AS. This study indicated that depression were more prevalent in AS patients than in controls. In this study, the pooled prevalence of depression in AS patients is 35% and higher than other chronic medical illnesses such as asthma (27%) [30], chronic obstructive lung disease (24.6%) [31], lupus (24%) [20] and rheumatoid arthritis (15%) [32]. This meta-analysis also revealed that small sample size and developing country of the studies conducted were significantly associated with increased depression prevalence, which might be explained that small studies often led to high prevalence estimates, and people with low socio-economic status (SES) in developing country was associated with increased susceptibility to depression [19].
Our sensitivity analyses indicated that depression prevalence estimates were relatively stable. Apart from the measurement tool used to ascertain depression, study quality and study population had impacts on the estimates detected. Our subgroup analyses found that variation in study sample size contributed importantly to the observed heterogeneity in the data. Studies with sample size <200 had higher depression estimates according to the HADS with a cutoff of 8 or more. Study quality might be a further explanation for the variance in prevalence estimates. Studies with lower total overall quality scores yielded higher depression estimates using the HADS with thresholds of 8.
We used rigorous methods to conduct the review and a reproducible, structured approach to data extraction and synthesis. The gold standard method was diagnostic interviews using ICD criteria, which were often time consuming and expensive, therefore, it was not ideal for investigating patients in a busy hospital environment [33]. Alternatively, self-report screening tools might be used. Although such self-reported questionnaires were quick and easy to complete and cheaper to use than diagnostic interviews in psychiatric practices, the different scales and cutoffs used to define the presence or the absence of depression could vary [33]. Such nature would lead to information bias and methodological heterogeneity when combining these data in a meta-analysis. It indicated that the rheumatologists should report prevalence at conventional cut-points, and screen for depression among AS patients according to the social and cultural contexts of the rheumatologists and patients in clinical practice.
However, this study still had some limitations. Firstly, a substantial amount of the heterogeneity among the studies remained unexplained by the variables examined. And there was inadequate data to conduct subgroup analyses according to variables of interest such as gender, disease duration and impact of age. A better understanding of social and cultural contexts of AS patients may help elucidate some of the root causes of depressive symptoms. Secondly, the data were derived from studies that used different designs and involved different groups of patients (e.g., different countries and years of publication), which might result in heterogeneity among the studies. Thirdly, the analysis relied on aggregated published data, which might result in potential publication bias.

CONCLUSIONS

One-third of people with AS experienced symptoms of depression. Depression was more prevalent in AS patients than in controls. Further research is needed to identify effective strategies for preventing and treating depression among AS patients.

Supplementary Materials

The online-only Data Supplement is available with this article at https://doi.org/10.30773/pi.2019.06.05.

ACKNOWLEDGEMENTS

The authors would like to thank all of the subjects for completing the article. This study was supported by Grants from the Chinese National Natural Science Foundation (Grant no. 71904118).

The authors have no potential conflicts of interest to disclose.

Author Contributions

Conceptualization: Lijuan Zhang. Data curation: Yaping Wu. Formal analysis: Lijuan Zhang. Methodology: Lijuan Zhang. Project administration: Weiyi Zhu. Resources: Shiguang Liu. Software: Yaping Wu. Supervision: Shiguang Liu. Validation: Weiyi Zhu. Writing—original draft: Lijuan Zhang. Writing—review & editing: Weiyi Zhu.

Figure 1.
Search results and study selection.
pi-2019-06-05f1.tif
Figure 2.
Prevalence of depression in ankylosing spondylitis patients.
pi-2019-06-05f2.tif
Figure 3.
Association between prevalence of depression in ankylosing spondylitis patients versus control group.
pi-2019-06-05f3.tif
Figure 4.
Association between score of depression in ankylosing spondylitis patients versus control group.
pi-2019-06-05f4.tif
Table 1.
Overview of prevalence studies of depression in AS patients
Study ID Country Participants Men, % Age, mean±SD/median (range), years Disease duration, mean±SD/median (range), years Criteria for detection of depression (cutoff) Prevalence, % NOS
Aissaoui 2012 Morocco 110 68.2 38.52±12.62 9 (0–40) HADS (≥8) 55.5 2
Altan 2003 NS 63 NS NS NS HADS (≥8) 33.3 1
Anyfanti 2012 Greece 44 68.8 NS NS Zung SDS (≥50) 18.2 1
Arisoy 2013 Turkey 9 88.9 39.4±10.1 10.6±7.6 HADS (≥7) 33 2
Aydin 2016 Turkey 37 62.3 34.67±7.90 7.16±2.49 HADS (≥8) 48.5 3
Baysal 2011 Turkey 243 86.4 34.65±10.36 6.02±6.60 HADS (≥7) 39.8 3
Cakar 2007 Turkey 52 100 32.85±12.11 9.09±7.36 21 Item-BDI (≥14/25) 50/13.5 2
Cooksey 2015 UK 348 77.0 56.0±13.0 22.0±15.0 HADS (≥11) 7.5 4
Demir 2013 Turkey 22 0 39.34±6.28 3.3±2.6 21 Item-BDI (≥14) 45.5 2
Dhakad 2015 India 100 100 34.42±9.78 4.84±0.06 HADS (≥8) 66 2
Durmus 2015 Turkey 80 63.8 39.33±10.98 10.88±10.08 21 Item-BDI (>17) 22.5 2
Ertenli 2012 Turkey 16 81.2 36.4 ±10.3 12.8±9.5 HADS (≥8) 43.8 2
Ersözlü-Bozkirli 2015 Turkey 29 79.3 34.4±10.3 4.1±6.2 21 Item-BDI (≥30) 37.9 2
Fallahi 2014 Iran 163 79.1 37.74±9.88 14.49±8.47 Structured interview 29.4 2
Günaydin 2009 Turkey 62 83.9 39.6±10.3 10.3±7.9 Zung SDS (≥50) 27.4 2
Hakkou 2011 Morocco 110 68.2 38.5±12.6 10.3±8.1 HADS (≥8) 55.5 2
Healey 2009 UK 612 71.6 50.8±12.2 10.3±8.1 HADS (≥8) 32.4 5
Hyphantis 2013 Greece 55 85.5 42.9±10.9 15.3±11.5 PHQ-9 (≥5/10) 40.7/14.8 2
Jiang 2015 China 683 80.4 27.33±8.67 6.47±6.47 Zung SDS (NS) 64 4
Li 2012 China 314 74.5 27.65±8.34 6.07±4.90 Zung SDS (≥50) 41.4 4
Lian 2003 China 60 78.0 36.0±12.0 >5 years (68%) Zung SDS (≥41) 43.3 2
Martindale 2006 UK 89 83.1 50 (18–77) 18 (12–29) HADS (≥11) 12.4 3
Meesters 2014 Sweden 1,738 65 54.5±14.3 NS Structured interview, ICD-10 10 3
Rodríguez-Lozano 2012 Spain 190 75 48.4±11.7 20.2±11 HADS (≥11) 11 2
Rostom 2013 Morocco 110 100 38.5±12.6 9 (0–40) HADS (≥8) 55.5 3
Schneeberger 2015 Argentina 64 89.1 44 (33–53) 17 (10.3–25) CES-D (≥16) 39.1 2
Shen 2016 China 2,331 64.9 36.50 (27.25–48.18) NS Structured interview, ICD-9 3.1 3
Xu 2016 China 103 75.7 32.9±10.7 NS Zung SDS (≥53) 36.9 2

NS: not stated, ID: identification, SD: standard deviation, AS: ankylosing spondylitis, HADS: Hospital Anxiety and Depression Scale, SDS: Self-rating Depression Scale, BDI: Beck Depression Inventory, PHQ: Patient Health Questionnaire, ICD: International Classification of Diseases, CES-D: Centre for Epidemiological Studies Depression Scale, NOS: Newcastle-Ottawa Scale

Table 2.
Overview of studies of depression in AS patients and control group
Study ID Country Study design Participants % of male in AS group % of male in control group Mean/median age (years) in AS group±SD (range) Mean/median age (years) in control group±SD (range) Mean disease duration of AS (years)±SD Depression measures NOS
Altan 2003 NS Case control 63 AS and 60 control NS NS NS NS NS HADS 1
Baysal 2011 Turkey Cross-sectional 243 AS and 118 control 86.4 78.8 34.65±10.36 36.53±9.26 6.02±6.60 HADS 3
Demir 2013 Turkey Case control 22 AS and 27 control 0 0 39.34±6.28 37.58±9.58 3.3±2.6 21 Item-BDI 2
Dhakad 2015 India Case control 100 AS and 100 control 100 100 34.42±9.78 36.39±8.07 4.84±0.06 HADS 2
Dincer 2007 Turkey Case control 68 AS and 45 control 100 100 32.9±11.0 30.1±6.24 NS 21 Item-BDI 1
Durmus 2015 Turkey Case control 80 AS and 80 control 63.8 71.2 39.33±10.98 36.41±10.84 10.88±10.08 21 Item-BDI 2
Ortancil 2010 Turkey Case control 29 AS and 20 control 69 60 42.0±9.7 38.2±12.5 9.4±7.7 SCL-90-R 2
Ozkorumak 2011 Turkey Case control 43 AS and 43 control 100 100 36.25±8.76 36.53±6.54 7.51±7.22 21 Item-BDI 2
Schneeberger 2015 Argentina Case control 64 AS and 95 control 89.1 89.5 44 (33–53) 40 (32–53) 17 (10.3–25) CES-D 2
Shen 2016 China Cohort 2,331 AS and 9324 control 64.9 64.9 36.50 (27.25–48.18) 36.50 (27.25–48.18) NS ICD-9 3
Xu 2016 China Cross-sectional 103 AS and 121 control 75.7 60.3 32.9±10.7 37.0±12.5 NS Zung SDS 2

NS: not stated, ID: identification, SD: standard deviation, AS: ankylosing spondylitis, HADS: Hospital Anxiety and Depression Scale, BDI: Beck Depression Inventory, SCL-90-R: Symptoms Checklist-90-Revised, CES-D: Centre for Epidemiological Studies Depression Scale, ICD: International Classification of Diseases, SDS: Self-rating Depression Scale, NOS: Newcastle-Ottawa Scale

Table 3.
Methods of detecting depression and summary of prevalence and heterogeneity findings
Tool Definition/cutoff No. of studies No. of participants Prevalence, % (95% CI) Heterogeneity I2, %
HADS ≥7 2 252 40 (34–46) 0
≥8 8 1,158 42 (39–45) 91.1
≥11 3 627 9 (6–12) 29.6
21 Item-BDI ≥14 2 74 49 (34–60) 0
>17 1 80 22 (13–32) -
≥25 1 52 14 (4–23) -
≥30 1 29 38 (20–56) -
Zung SDS >41 1 60 43 (31–56) -
≥50 3 420 30 (15–44) 87.0
≥53 1 103 37 (28–46) -
NS 1 683 64 (60–68) -
Structured interview (e.g., ICD) 3 4,232 13 (6–20) 98.4
 CES-D ≥16 1 64 39 (27–51) -
 PHQ-9 ≥5 1 55 41 (28–54) -
≥10 1 55 15 (5–24) -

NS: not stated, HADS: Hospital Anxiety and Depression Scale, BDI: Beck Depression Inventory, SDS: Self-rating Depression Scale, ICD: International Classification of Diseases, CES-D: Centre for Epidemiological Studies Depression Scale, PHQ: Patient Health Questionnaire

Table 4.
Impact of study characteristics on prevalence estimates for depression in AS: sensitivity and subgroup analyses
Prevalence estimates for depression in AS patients
Prevalence of depression in AS patients versus control group (RR) Scores of depression in AS patients versus control group (SMD)
HADS (≥8) HADS (≥11) Zung SDS (≥50) Structured interview
Primary analysis 42 (39, 45) 9 (6, 12) 30 (15, 44) 13 (6, 20) 1.76 (1.21, 2.55) 0.43 (0.19, 0.67)
I2=91.1% I2=29.6% I2=87.0% I2=98.4% I2=75.8% I2=64.7%
8 studies 3 studies 3 studies 3 studies 8 studies 7 studies
1,158 AS 627 AS 420 AS 4,232 AS 3,006 AS/9,925 control 549 AS/428 control
Sensitivity analyses
 Excluding studies with less sample representativeness - - - 7 (0, 13) - -
I2=98.6%
2 studies
4,069 AS
 Excluding studies with less comparable respondent and non-respondent comparability 45 (28, 62) 9 (5, 13) - - - -
I2=91.3% I2=40.9%
3 studies 2 studies
759 AS 437 AS
 Excluding studies only using male sample 45 (34, 56) 9 (6, 12) 30 (15, 44) 13 (6, 20) 1.85 (1.24, 2.75) 0.28 (0.13, 0.43)
I2=87.0% I2=29.6% I2=87.0% I2=98.4% I2=64% I2=0%
6 studies 3 studies 3 studies 3 studies 7 studies 5 studies
948 AS 627 AS 358 AS 4,232 AS 2,906 AS/9,825 control 438 AS/340 control
Subgroup analyses
 Sample size
  <200 52 (44, 60) 11 (8, 15) 23 (14, 32) - 3.72 (1.33, 10.38) 0.49 (0.22, 0.75)
I2=70.0% I2=0% I2=22.1% I2=87% I2=59%
7 studies 2 studies 2 studies 6 studies 6 studies
546 AS 279 AS 108 AS 432 AS/483 control 306 AS/310 control
  ≥200 - - - 7 (0, 13) 1.48 (1.06, 2.06) -
I2=98.6% I2=40%
2 studies 2 studies
4,069 AS 2574 AS/9442 control
Overall quality
 <3 points (low quality) 52 (41, 63) - 23 (14, 32) - 3.72 (1.33, 10.38) 0.49 (0.22, 0.75)
I2=79.4% I2=22.1% I2=87% I2=59%
5 studies 2 studies 6 studies 6 studies
399 AS 108 AS 432 AS/483 control 306 AS/310 control
 ≥3 points (high quality) 45 (28, 62) 9 (5, 13) - 7 (0, 13) 1.48 (1.06, 2.06) -
I2=91.3% I2=40.9% I2=98.6% I2=40%
3 studies 2 studies 2 studies 2 studies
759 AS 437 AS 4,069 AS 2,574 AS/9,442 control
Publication year
 2000s 32 (29, 32) - - - - -
I2=0%
2 studies
675 AS
 2010– 57 (52, 62) 9 (5, 12) 30 (8, 53) 7 (0, 13) 2.98 (1.47, 6.06) 0.43 (0.15, 0.70)
I2=18.2% I2=41.7% I2=92.3% I2=98.6% I2=88% I2=70%
6 studies 2 studies 2 studies 2 studies 7 studies 6 studies
483 AS 538 AS 358 AS 4,069 AS 2,943 AS/9,865 control 481 AS/383 control
Country of origin
 Asia 55 (41, 70) - 35 (22, 49) 16 (-10, 12) 3.27 (1.41, 7.58) 0.44 (0.15, 0.72)
I2=62.0% I2=79.7% I2=98.1% I2=90% I2=70%
3 studies 2 studies 2 studies 6 studies 6 studies
153 AS 376 AS 2,494 AS 2,879 AS/9,770 control 485 AS/333 control
 Europe - 9 (6, 12) - - - -
I2=29.6%
3 studies
627 AS
 Africa 56 (50, 61) - - - - -
I2=0%
3 studies
330 AS

AS: ankylosing spondylitis, HADS: Hospital Anxiety and Depression Scale, SDS: Self-rating Depression Scale, RR: relative risk, SMD: standardized mean difference

Table 5.
Pearson’s and Spearmen’s correlation between study characteristics and prevalence estimates
Study characteristic Depression prevalence estimate
No. of studies r p
Male, % 27 0.153 0.445
Mean/medium age, year 27 -0.054 0.790
Mean/medium disease duration, year 27 -0.035 0.861
Sample size 28 -0.450* 0.016
Representativeness 28 -0.215 0.272
Comparability 28 -0.066 0.737
Overall quality 28 -0.055 0.780
Country of origin 27 -0.613 0.001
Publication year 28 0.108 0.585

* p<0.05,

p<0.01

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