Therapeutic Benefit of Balneotherapy and Hydrotherapy in the Management of Fibromyalgia Syndrome

A Qualitative Systematic Review and Meta-analysis of Randomized Controlled Trials

Johannes Naumann; Catharina Sadaghiani


Arthritis Res Ther. 2014;16(R141) 

In This Article


Literature Search

The literature search revealed 107 citations in accordance with the predefined search terms "FMS" and "BT" or "HT" and "RCT". One additional study each was found in the reference lists of published reviews and the reference list of an already identified study: 52 duplicates were removed. A further 20 records were excluded because they did not fulfill the inclusion criteria (no papers on FMS and/or BT/HT (n = 7);[24–30] different outcome measure (cost-effectiveness) (n = 2);[31,32] reviews[33,34] (n = 2); no control group[35–38] (n = 4); not randomized[39–42] (n = 4); HT not the main treatment[43] (n = 1)).

Of the 37 articles that were assessed, four were excluded because of insufficient data reporting.[7,44–46] A further three studies were excluded because the main treatment (BT/HT) was the same both in the treatment and control group (Altan et al.:[47] baths in mineral water with and without exercise; Ammer and Melnizky:[48] whirl baths with and without etheric oils; Calandre et al.:[49] baths with two different kind of exercises). The remaining 30 articles included 2 reporting follow-up data to already included studies,[50,51] and a further 4 reporting on the same study publication but with different outcome measures.[52–55]

Finally, 24 studies met our inclusion criteria and were included in the qualitative analysis. Of these, 12 reported on HT[56–67] and 12 on BT:[68–79] 21 studies were suitable for quantitative analysis, 11 of which reported on HT and 10 on BT. Three studies had to be excluded from the quantitative analysis due to insufficient data reporting (HT:;[59] BT:[75,76]), (see Figure 1).

Figure 1.

Flowchart of the results of the literature search. BT, balneotherapy; HT, hydrotherapy; FMS, fibromyalgia syndrome.

Description of Included Trials

The characteristics of the included studies are detailed in the following tables (see Additional files 1 and 2 The studies were separated according to treatment modalities: Additional file 1 HT with the subgroups, HT with exercise (n = 10) and hydrogalvanic (Stanger) bath (n = 2). Additional file 2 BT with the subgroups mineral water (n = 3), spa therapy (n = 3), sulfur bath (n = 2), thalassotherapy (n = 1), phytothermotherapy (n = 1), mud (n = 1), acratothermal water (n = 1). Study characteristics for all trials included in qualitative synthesis are summarized below.

Patient Characteristics

Participants' age across the studies ranged from 18 to 73 years. The median of the mean age in the treatment group was 45.2 years compared to 46.3 years in the control group. Disease duration was reported in 19 studies and ranged from 1.3 to 24.0 years. The median of mean disease duration was 8.4 years. Over 96% of the participants were women. Sixteen studies involved women only,[56,57,62–71,73,75–77] and eight studies included both women and men.[58–61,72,74,78,79] The median of the mean pain baseline values reported in 20 studies was 7.1 (5.5 to 9.1). Pain scores were assessed in the four remaining studies but not reported separately.[57,73,74,76]

Study Characteristics

Origin of Studies. Two RCTs originated from Canada,[59,60] eight from Turkey,[57,58,69,71,72,75,77,78] two from Brazil,[56,68] one from Israel (Dead sea),[70] two from Italy,[73,74] one from Austria,[61] three from Spain,[62,66,67] one from Norway,[63] two from Sweden,[64,65] one from Germany[76] and one from The Netherlands.[79]

Setting. Eighteen studies were conducted in outpatient settings[56,58–69,72–74,76,78] and six in inpatient settings.[57,70,71,75,77,79] Seven studies were conducted within spa resorts either with in-patients or outpatients.[69–71,73,74,77,79] Patients were referred from primary, secondary and tertiary care settings.

Inclusion and Exclusion Criteria. In all the studies, FMS was diagnosed according to the ACR criteria.[80] Patients with severe diseases were excluded in 18 studies[56–58,60,62–69,72–76,79] and patients with mental disorders and/or on antidepressant drugs in 11 studies;[57,58,60,62,64–67,72,75,76] 6 studies didn't report exclusion criteria.[59,61,70,71,77,78]

Reporting of Adverse Events. Adverse events were reported in four studies.[56,65,68,79] In all cases the adverse events were not indicated as a cause of interruption or dropouts. Seven studies[57,58,72–75,78] clearly reported that there were no adverse events. The remaining 13 studies gave no information on adverse events. No serious adverse events were reported (for details see Additional files 1 and 2

Intervention Characteristics

HT interventions used, among others, hydrogalvanic/Stanger bath in two studies[57,61] and exercises in plain water.[56,58–60,62–67] BT interventions were spa therapy,[71,77,79] thalassotherapy,[68] phytothermotherapy,[73] mud,[74] sulfur bath,[70,76] baths in mineral/thermal water[69,72,78] and in acratothermal water.[75] Treatment duration in the HT group ranged from 5.0 to 32.0 weeks, with a median of 15.5 weeks, in contrast to BT studies with shorter duration ranging from 1.5 to 12.0 weeks and a median of 2.0 weeks. Median follow-up duration was similar for both HT and BT at 2.5 and 3.5 months respectively.

Outcome Measures

Different VAS were used to measure pain. Four studies did not report how pain was measured.[57,73,74,76] Twenty studies used the Fibromyalgia Impact Questionnaire (FIQ) to measure HRQOL. Nine studies[56,58,60,68,69,71,72,75,79] measured depressed mood by the Beck Depression Inventory (BDI).

Risk of Bias

Only 5 of the 24 studies included had low risk of bias;[56,57,64,67,68] a further 5 were assigned as having unclear risk (studies with one unclear judgement; unclear allocation:;[65,71,77] selective reporting:;[66] unclear outcome assessment blinding:[79]). The remaining 14 studies were at high risk of bias, as they had two or more unclear judgements in the key domains, including 5 studies with serious flaws in one or more key domains.[59,60,63,75,76] For details see categorization of risk of bias at the individual study level (see Additional file 3

Sequence Generation and Treatment Allocation. Of 24 studies, 10 had unclear risk of selection bias in both domains, 2 were considered to be at high risk because of serious randomization flaws.[59,75] Half the studies reported adequate randomization, but only seven adequate allocation concealment.[4,6,21,47,52,69,80]

Similar Baseline. All studies had low risk of selection bias with the exception of two, one with unclear risk (unclear reporting;[76]) and one with high risk due to significant differences in baseline characteristics in a major FMS symptom (TPC)[63]).

Blinding of Participants and Personnel. Performance bias was not considered a key domain. Due to the participatory nature of BT and HT blinding is not feasible.

Incomplete Outcome Data. Of the 24 studies, 19 were assigned low risk of attrition bias (criteria: attrition rate reported, not exceeding 20% or intention-to-treat analysis). Five studies were assigned unclear or high risk of bias because two had high dropout rates[60,63] (high risk of bias) and the dropout rate was not clearly reported in three studies.[70,76,78]

Selective Reporting. Two studies were assigned high risk of bias;[59,75] thus, reporting was insufficient and not in alignment with the values presented in tables. A further five had unclear risk of reporting bias due either to double reporting[66,70] or incomplete/inconsistent outcome reporting.[60,61,63]

Blinding of Outcome Assessment. Fifteen of the 24 studies had low risk of detection bias for outcome assessment, eight had unclear risk,[58,59,61,62,69,72,75,79] and one was assigned a high risk of bias[76] (see Additional file 4

Subgroup Analyses

Hydrotherapy. Meta-analyses showed moderate-to-strong evidence (consistent findings among multiple (≥3) RCTs with low risk of bias) for a small reduction in pain with exercises (pool-based exercise (PBE) in plain water (HT) at the end of treatment; SMD −0.42; 95% CI −0.61, −0.24; P <0.00001; I2 = 0% (eight studies: three low-risk studies,[56,64,67] two unclear-risk studies,[65,66] three high-risk studies[58,62,63]). Concerning HRQOL (FIQ) at the end of treatment, there was moderate-to-strong evidence for a small improvement; SMD −0.40; 95% CI −0.62, −0.18; P = 0.0004; I2 = 15% (seven studies: three low-risk studies,[56,64,67] two unclear-risk studies,[65,66] two high-risk studies[60,62]). For depressive symptoms (BDI) and TPC no significant effect was seen at the end of treatment (BDI: SMD −0.19; 95% CI −0.88, 0.50; P = 0.59; I2 = 60% (one low-risk[56] and one high-risk study[60]); TPC: SMD −0.37; 95% CI −1.12, 0.38; P = 0.33; I2 = 79% (one unclear risk[66] and two high-risk studies[58,60]) (see Figure 2).

Figure 2.

Treatment effects of exercises in plain water (hydrotherapy, HT) at the end of treatment. PBE, pool-based exercise; +E, plus education; VAS, visual analog scale; FIQ, fibromyalgia impact questionnaire; BDI, Beck depression inventory.

Comparison Group. Subgroup analysis of the type of comparison group suggests that RCTs comparing HT to no treatment (usual care) or other types of active control had a significant effect, but not when compared to land-based exercise (see Additional file 5

Balneotherapy. Meta-analyses showed moderate evidence for a large reduction of pain at the end of treatment with BT in mineral/thermal water, regardless of whether within a spa center (SPA) or not: SMD −0.84; 95% CI −1.36, −0.31; P = 0.002; I2 = 63% (five studies: two unclear-risk studies[71,77] and three high-risk studies[69,72,78]). Moderate evidence was seen for a medium improvement in HRQOL (FIQ); SMD −0.78; 95% CI −1.13, −0.43; P <0.0001; I2 = 0% (four studies: two unclear-risk[71,77] and two high-risk studies[69,72]). Moderate evidence for a large improvement was seen for TPC: SMD −0.83; 95% CI −1.42, −0.24; P = 0.006; I2 = 71% (five studies: two unclear-risk[71,77] and three high-risk studies[69,72,78]). There was no significant effect on depressive symptoms (BDI) at the end of treatment (SMD −0.87 −1.82, 0.08; P = 0.07; I2 = 85% (four studies: two unclear-risk[71,77] and two high-risk studies[69,72]) (see Figure 3).

Figure 3.

Treatment effects of balneotherapy (BT) in mineral/thermal water (MW), within a spa center (SPA) or not, at the end of treatment. VAS, visual analog scale; FIQ, fibromyalgia impact questionnaire; BDI, Beck depression inventory.

Follow up

Findings at follow up showed that a small reduction of pain was maintained for HT and BT: SMD −0.25; 95% CI −0.50, −0.01; P = 0.04; I 2 = 0% for HT and SMD −0.30; 95% CI −0.53, −0.07; P = 0.01; I 2 = 0% for BT. Only BT showed significant results for HRQOL (FIQ) (SMD −0.35; 95% CI −0.61, −0.10; P = 0.006; I 2 = 0%). With regard to TPC and BDI, only BT studies provided follow-up data with SMD −0.39; 95% CI −0.73, −0.05; P = 0.03; I 2 = 35% for TPC and SMD −0.31; 95% CI −0.59, −0.03; P = 0.03; I 2 = 0% for BDI (see Figure 4).

Figure 4.

Treatment effect of hydrotherapy (HT)/balneotherapy (BT) at follow up. VAS, visual analog scale; FIQ, fibromyalgia impact questionnaire; BDI, Beck depression inventory.

Analysis of Overall Effects

Taking into account all available studies, regardless of treatment modality, meta-analysis provided moderate evidence for a medium reduction of pain at the end of treatment; SMD −0.57; 95% CI −0.77, −0.38; P <0.00001; I 2 = 45%. Results are shown for HT, BT and diverse treatments: hydrogalvanic bath (Stanger), mud therapy, sulfur bath and thalassotherapy (see Additional file 6

Sensitivity Analyses

Sensitivity analysis according to potential risks of bias showed no significant difference between the effect size of pain (HT) at the end of treatment and risk of bias (see Additional file 7 Analysis according to sample size (<25, >25) shows a slightly larger effect size and broader CIs in small studies (P = 0.54) (see Additional file 8

Statistical heterogeneity of analysis for the effect size of pain in the BT group (I2 = 63%) was substantially decreased (I2 = 0%) by removing the study of Ardiç et al.[69] (pharmacological co-therapies not allowed; non-intervention control group). The magnitude of the effect size was decreased to SMD −0.58; 95% CI −0.91, −0.26, P = 0.0004, corresponding to a medium effect.

Publication Bias

Visual analysis of the funnel plot shows a symmetric picture, with one outlier study already identified by sensitivity analysis.[69] This indicates that the results of the meta-analysis can be regarded as robust against potential reporting bias (see Additional file 9