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ORIGINAL ARTICLE
Infrared sauna in patients with rheumatoid arthritis
and ankylosing spondylitis
A pilot study showing good tolerance, short-term improvement of pain and stiffness,
and a trend towards long-term beneficial effects
Fredrikus G. J. Oosterveld & Johannes J. Rasker &
Mark Floors & Robert Landkroon & Bob van Rennes &
Jan Zwijnenberg & Mart A. F. J. van de Laar &
Gerard J. Koel
Received: 31 March 2008 / Revised: 1 July 2008 /Accepted: 11 July 2008 / Published online: 7 August 2008
#
The Author(s) 2008
Abstract To study the effects of infrared (IR) Sauna, a
form of total-body hyperthermia in patients with rheuma-
toid arthritis (RA) and ankylosing spondylitis (AS) patients
were treated for a 4-week period with a series of eight IR
treatments. Seventeen RA patients and 17 AS patients were
studied. IR was well tolerated, and no adverse effects were
reported, no exacerbation of disease. Pain and stiffness
decreased clinically, and improvements were statistically
significant (p<0.05 and p<0.001 in RA and AS patients,
respectively) during an IR session. Fatigue also decreased.
Both RA and AS patients felt comfortable on average
during and especially after treatment. In the RA and AS
patients, pain, stiffness, and fatigue also showed clinical
improvements during the 4-week treatment period, but
these did not reach statistical significance. No relevant
changes in disease activity scores were found, indicating no
exacerbation of disease activity. In conclusion, infrared
treatment has statistically significant short-term beneficial
effects and clinically relevant period effects during treat-
ment in RA and AS patients without enhancing disease
activity. IR has good tolerability and no adverse effects.
Keywords Ankylosing spondylitis
.
Hyperthermia
.
Inflammation
.
Infrared sauna
.
Physical therapy modalities
.
Rheumatoid arthritis
Introduction
Since Hippocratic times, heat treatment has been popular
among people with rheumatic disorders. The evidence for
their application is still weak, despite the fact that several
studies investigating the effects of heat in rheumatic
diseases have been conducted [1, 2]. Superficial heat can
be used in rheumatoid arthritis and low back pain as a
palliative therapy and can be recommended for beneficial
short-term effects, but these recommendations are limited
by methodological considerations such as the poor quality
of trials [3, 4].
Finnish saunas, a well-known form of total-body heating,
showed good clinical effects for rheumatic patients [5, 6].
The so-called whole-body hyperthermia has also been
widely used during the last century, especially in Germany
and Eastern European countries and was known as “fever
treatment” [7]. Although beneficial effects of total-body
hyperthermia have been reported [8 , 9], controlled studies
have not been performed, and the method is not often used
in Western Europe.
During the past 10 years, a new modality for whole-body
hyperthermia, named infrared (IR) sauna, has become
Clin Rheumatol (2009) 28:29–34
DOI 10.1007/s10067-008-0977-y
F. G. J. Oosterveld (*)
:
M. Floors
:
R. Landkroon
:
B. van Rennes
:
J. Zwijnenberg
:
G. J. Koel
Expertise Center Health, Social Care and Technology,
Saxion University of Applied Sciences,
P.O. Box 70.000, 7500 KB Enschede, The Netherlands
e-mail: f.g.j.oosterveld@saxion.nl
J. J. Rasker
:
M. A. F. J. van de Laar
Department of Communication Studies, Faculty of Behavioral
Sciences and Philosophy, University Twente,
Enschede, The Netherlands
M. A. F. J. van de Laar
Department of Rheumatology, Medisch Spectrum Twente,
Enschede, The Netherlands
available in the Europe. It is a compact and user-friendly IR
“whole-body hyperthermia.” Personal experiences of rheu-
matoid arthritis (RA) and ankylosing spondylitis (AS)
patients in our out-patients clinic appeared to be promising.
They experienced less pain and imp roved physical func-
tioning. Despite the theoretical possibility of negative
effects on disease activity, in our clinical series, no
aggravation of inflammation activity was seen.
The new IR cabin differs from the traditional Scandinavian
saunas. The heating effect of a high ambient temperature is
comparable, but due to the addition of infrared radiation, some
heat penetrates maximally up to 4 mm into the superficial skin
[10]. As this might result in different physiological responses
compared to the Finn ish sauna, we first studied the
physiological effects of infrared whole-body treatment in
healthy subjects before starting clinical trials in rheumatic
patients [11]. Fifteen healthy subjects were exposed to total-
body heat treatment in an infrared cabin at three different
intensities (40°C, 55°C, and 70°C). Mean skin surface
temperature (2.6°C, 6.8, and 9.1°C, respectively), core
temperature (0.4°C, 0.5°C, and 0.6°C, respectively), and
heart rate (+14, +37, and +58 beats per minute, respectively)
increased significantly. Significant loss of bodyweight after
treatment was also found (0.1, 0.3, and 0.4 kg, respectively).
In general, a small decrease of systolic and diastolic blood
pressure was shown.
The purpose of this study was to determine whether
these previously found physiological changes would also
provide beneficial effects in patients w ith rheumatic
disorders. The more explicit research questions, therefore,
are:
1. What is the effect of IR sauna on body functions and
structures, such as pain, stiffness, and fatigue (primary
outcomes)?
2. What is the effect of IR on physical activities and
(social) participation (secondary outcomes)?
3. Are there any side effects regarding c omfort and
tolerance during treatment and disease activity (tertiary
outcomes)?
Patients and methods
Inclusion criteria People with RA according to the revised
American Rheumatism Association [12 ]orwithAS
according to the New York [13] criteria between 18 and
70 years of age and only patients with chronic disease that
had been stable for at least 3 months without change in
medication were included.
Exclusion criteria Patients with a change of treatment
during 3 months prior to the start of the study; patients
with signs of acute inflammatory activity (morning stiffness
lasting longer than 1 h or more than three joints actively
inflamed) as judged by the consulting rheumatologist (heat
treatment may aggravate clinical signs and inflammatory
activity in an acute phase of the di sease); patients
permanently wheelchair-bound or bedridden; patients with
the following comorbidities: heart disease, skin disease,
malignancy, asthmatic bronchitis, or psychiatric disorders
are excluded.
Patients were recruited consecutively from the rheuma-
tology out-patients clinic (JJR) in a general district hospital
in Enschede, The Netherlands.
After oral and written information about the study and
the possible clinical effects of IR whole-body hyperthermia,
patients were invited to participate. Informed consent was
obtained from all patients, according to the Declaration of
Helsinki.
Treatment The patients were treated in the Health Company
Infrared Cabin (kindly made available by The Health
Company, P.O. Box 321, 2400 AH Alphen a/d Rijn, the
Netherlands), which was 130×90×190 cm in size. The
temperature in the cabin can be adjusted from normal
ambient room temperature up to 90°C. The patients were
seated in the infrared cabin, which has six heating sources;
three at the back, two in front besides the entrance, and one
under the bench behind the lower legs of the patients. The
infrared used has a long wavelength between 5,000 and
1,000,000 nm.
The patients were treated for a perio d of 4 weeks, twice
weekly, with eight IR sessions in the IR cabin (30 min at an
ambient temperature of 55°C). According to the manufac-
turers’ recommendation, before treatment, a preheating time
of the IR whole-body hyperthermia equipment of 15 min was
used. During the whole study period , the dosages of
nonsteroidal anti-inflammatory drugs and disease-modifying
antirheumatic drugs were not changed; treatments with
physiotherapy, when applied, were not changed, and no
corticosteroid injectio n was given
Measurements Clinical measurements were performed
4 weeks before the start, at the start, and at the end of the
4-week period of IR treatments and 4 weeks after the end of
the treatment series; all four assessments were at the same
time of the day and executed by a trained physiotherapist
unaware of the study protocol. The pretreatment period
without IR sauna was meant as a control and the 4 weeks
after treat ment as follow-up.
The patient’s perceptions of pain [14], stiffness [15], and
fatigue [
16–18] were measured on a 100-mm visual analog
scale and were considered as primary outcomes.
Secondary outcomes for the RA patients were: Escola
Paulista de Medicina Range of Motion (EPM-ROM scale)
30 Clin Rheumatol (2009) 28:29–34
[19] and activities and participation scales of the Dutch
Arthritis Impact Measurement Scales (DUTCH-AIMS)
[20]. For AS patients, Bath Ankylosing Spondylitis Global
Score [21], the Bath Ankylosing Spondylitis Metrology
Index (BASMI, a ROM-index) [22], and the Bath Anky-
losing Spondylitis Functional Index [23] were used. To
evaluate possible effects on the disease activity (improve-
ment or exacerbation) for RA patients, the Disease Activity
Score using 28 joints (DAS 28) [24] was calculated, and for
AS pat ients, the Bath Ankylosing Spondylitis Disease
Activity Index (BASDAI) [25] and the erythrocyte sedi-
mentation rate (ESR) after 1 h were assessed. The DAS 28,
BASDAI, and ESR were considered as tertiary outcomes.
These measurements are fairly routine in clinical research
and have been proven to be valid, reliable, and of good
sensitivity to change [14–25].
Short-term effects Directly before and after the first IR
treatment, the primary outcomes were registered to measure
the immediate effect of IR on pain, stiffness, and fatigue.
Besides that, during and after the first treatment, well-being
(as tertiary outcome) was recorded on a five-point Likert scale
(very uncomfortable, uncomfortable, neutral, comfortable,
and very comfortable). Well-being was measured at 15 and
30 min after the start of the treatment (patient still in the cabin)
and 30 min after the end of treatment (patient out of cabin).
Statistics The continuous data were checked for normality .
This was done with the descriptive statistics explore command
in Social Package for Social Sciences (SPSS) 14.0 [26]by
making histograms, scatter graphs, normality plots, normal
curves, and carrying out normality tests (Kolmogorov–
Smirnov and Shapiro–Wilk). Continuous data were statisti-
cally analyzed by means of repeated measure analysis with
Bonferroni correction within SPSS 14.0. Results are
expressed as mean and SEM (Standard Error of Mean).
For nonparametric data (well-being on an ordinal Likert
scale), Wilcoxon signed-rank test for related samples was
applied. Level of significance (α) was chosen at 0.05.
Ethics The ethical committee of the Hospital Medisch
Spectrum Twente, Enschede, The Netherlands approved
the study design.
Results
Patient characteristics Of 37 patients approached, one
declined (could not participate due to nonmedical reasons)
and 36 were enrolled into the study. A total of 18 patients
with rheumatoid arthritis and 18 patients with ankylosing
spondylitis entered the study with mean age of 47 and
44 years, respectively (Table 1).
One RA and one AS pa tient dropped ou t in the
pretreatment period due to exacerbation of RA and acute
lumbar nerve root compression, respectively, and could not be
measured for follow-up. Therefore, the mean group results of
17 RA and 17 AS patients are presented. Functional capacity
of RA patients according to Steinbröcker classification [27]is
shown in Table 2.
Immediate effects of IR whole-body hyperthermia Pain and
stiffness significantly decreased clinically (p<0.05 and p<
0.001 in RA and AS patients, respectively) during an IR
session (Table 3). Fatigue also improved, but this did not
reach statistical significance.
Delayed effects during and 4 weeks after treatment on
primary outcomes In RA patients, pain, stiffness, and
fatigue showed slight improvements during the 4-week
treatment period; stiffness a lmost reached statistical signif-
icance: p=0.06 (Table 4). In the AS patients, stiffness
improved after the treatment, but this did not reach
statistical significance (
p=0.30); otherwise, small or no
effect were seen during the treatment and post-treatment
periods (Table 4).
Table 1 Patient characteristics
RA patients AS patients
Gender 3 male, 15 female 13 male, 5 female
Age 47 SD 13 (26–70) 44 SD 10 (23–57)
Disease duration 13 SD 10 (3–29) 21 SD 10 (4–40)
Mean in years, SD (minimum–maximum)
RA Rheumatoid arthritis, AS ankylosing spondylitis
Table 2 Steinbröcker classification of rheumatoid arthritis patients
(n=17)
Stage Number of patients
I2
II 8
III 6
IV 1
Table 3 Immediate effects of IR sauna treatment
Pain Stiffness Fatigue
Before After Before After Before After
RA 25 (5) 15 (5)* 25 (5) 12 (3)* 35 (7) 30 (7)
AS 26 (4) 11 (3)** 40 (6) 16 (4)** 37 (6) 28 (6)
VAS, 0–100 mm; mean (SEM)
IR infrared, RA rheumatoid arthritis, AS ankylosing spondylitis
*p<0.05, **p<0.001
Clin Rheumatol (2009) 28:29–34 31
Delayed effects during and 4 weeks after treatment on
secondary outcomes Over the 12-week study period, no
statistically significant change was found on secondary
clinical and f unctional variables, such as ROM and
DUTCH-AIMS for RA patients (Table 5)andBath
Ankylosing Spondylitis scores for AS patients (Table 5).
However, there is a clear clinical improvement of RA
patients on the physical, affective, and symptom scales of
the DUTCH-AIMS. The effect persisted during the post-
treatment phase on the physical and affective scales.
Well-being during and after treatment (tertiary outcomes)
The RA patients felt comfortable during and after the
treatment session. Especially after treatment, 59% felt
comfortable and many felt even very comfortable (29.4%;
Table 6). There was no statistically significant difference in
well-being as measured at the three instances. The AS
patients felt less comfortable during the treatment but after
half an hour, almost all of them felt (very) comfortable
(Table 6). The perceived well-being 30 min after treatment
in AS patients showed better statistically significance
compared to the other two measurement points (p<0.01).
Influence on disease activity No relevant change in disease
activity measurem ents as reflected by DAS 28 in RA
patients and BASDAI and ESR in AS patients was found,
indicating no unwanted exacerbation of disease during or
after IR treatment, and no other side effect was reported (for
example fainting and headache; Table 5).
Discussion
In all patients, a clinically relevant improvement was seen
during the IR sauna treatment with pain and stiffness
decreasing 5 to 24 points on the VAS. Pain reduced
approximately 40% and 60% and stiffness approximately
50% and 60% for patients with RA and AS, respectively
(Table 3). All patients felt well during and after IR
treatment, and 30 min after the end of treatment, 88.2%
of patients felt “comfortable” or “very comfortable”
(Table 6).
In RA patients, a clinically relevant improvement is seen
during the 4 -week treatment period compared to the
Table 4 Outcome primary effect variables 4 weeks before IR sauna,
at start and end of the 4-week treatment period and 4 weeks after
treatment
Pretreatment Start
treatment
End of
treatment
Post-
treatment
RA patients
Pain 30 (5) 29 (6) 24 (5) 27 (4)
Stiffness 28 (6) 27 (5) 17 (5)* 23 (5)
Fatigue 37 (6) 36 (6) 33 (6) 39 (7)
AS patients
Pain 26 (6) 26 (4) 30 (5) 27 (6)
Stiffness 40 (7) 38 (6) 32 (7) 31 (7)
Fatigue 34 (7) 37 (7) 35 (7) 30 (7)
VAS, 0–100 mm; mean (SEM)
IR Infrared, RA rheumatoid arthritis, AS ankylosing spondylitis
*p=0.06
Table 5 Outcome secondary and tertiary effect variables 4 weeks before IR sauna, at start, and end of the 4-week treatment period and 4 weeks
after treatment
Pretreatment Start treatment End of treatment Post-treatment
RA patients
EPM-ROM 6.2 (0.6) 5.6 (0.6) 5.8 (0.7) 5.6 (0.6)
AIMS physical 2.3 (0.4) 2.6 (0.6) 1.6 (0.4) 1.7 (0.4)
AIMS affective 2.9 (0.3) 3.1 (0.5) 2.2 (0.3) 2.3 (0.4)
AIMS symptoms 4.0 (0.5) 4.0 (0.5) 3.3 (0.5) 3.9 (0.5)
AIMS social 4.3 (0.4) 3.8 (0.4) 3.7 (0.4) 4.2 (0.5)
DAS 28 3.96 (0.30) 3.74 (0.34) 3.58 (0.31) 3.63 (0.32)
AS patients
BASGS (last week) 3.4 (0.7) 3.1 (0.7) 2.9 (0.7) 3.2 (0.8)
BASGS (26 weeks) 3.9 (0.7) 3.5 (0.7) 3.7 (0.8) 4.1 (0.8)
BASMI 2.0 (0.5) 2.4 (0.5) 2.2 (0.5) 2.3 (0.5)
BASFI 3.3 (0.6) 3.2 (0.6) 3.2 (0.6) 3.1 (0.6)
BASDAI 3.4 (0.5) 3.4 (0.6) 3.4 (0.6) 3.2 (0.6)
ESR 17 (3) 16 (4) 14 (2) 15 (3)
Mean (Standard error of the mean); low scores are better scores
IR Infrared, RA rheumatoid arthritis, AS ankylosing spondylitis, EPM-ROM Escola Paulista de Medicina Range of Motion score, AIMS Arthritis
Impact Measurement Scales, DAS 28 Disease Activity Score, BASG Bath Ankylosing Spondylitis Global Score, BASMI Bath Ankylosing
Spondylitis Metrology Index, BASFI Bath Ankylosing Spondylitis Functional Index, BASDAI Bath Ankylosing Spondylitis Disease Activity
Index, ESR erythrocyte sedimentation rate
32 Clin Rheumatol (2009) 28:29–34
pretreatment period, regarding pain and stiffness dim inish-
ing 5–10 points on the VAS, while during the previous
nontreatment period , t here was n o noticeable change
(Table 4). During the post-treatment period, these effects
were lost. These effects are less obvious in AS patients
(Table 4).
In RA patients, the physical, affective, and symptoms
scales of the DUTCH-AIMS showed a trend of improve-
ment during treatment, persisting during the post-treatment
phase on the physical and affective scale (Table 5). It is not
surprising that no relevant change was seen on the social
scale because it cannot be expected that this period would
have any influence on the relationship of a patient with
family, friends, and relatives as measured on the social
scale.
In the AS patients group, there are no changes on BAS
global scores and functional index over time (Table 5).
Apparently, IR whole-body hyperthermia does not have
major effects on these domains.
No relevant change on EPM-ROM and BASMI in RA
and AS patients, respectively, were found, so IR treatment
does not seem to have any direct effect on the overall range
of motion (Table 5). Probably, the impaired ROM in non-
acutely inflamed joints, as was the case in our series, is
mainly due to irreversible change in these joints, such as
erosions and cartilage damage in RA patients and calcifi-
cation of joint ligaments or bony outgrowth in AS patients.
Therefore, no majo r imp rovement could have been
expected without adequate additional exercises.
The effect of IR whole-body hyperthermia upon local
joint inflammation or disease activity is not clear. The
findings of earlier studies were controversial [9, 28–33],
and many studies have poor or no optimal quality as
summarized in the COCHRANE study [3]. For that reason,
we have monitored disease activity as reflected by DAS 28
in RA patients and BASDAI and ESR in AS patients. No
relevant change in these disease activity measurements was
found, indicating no unwanted side effects of IR treatment
(Table 5). This does not exclude that some individual cases
may experience increased complaints during or after
treatment.
From this study, it appears that IR whole-body hyper-
thermia has direct beneficial effects. Although in the long-
term, there is a tenden cy toward improvement of clinical
symptoms of RA and AS patients, there is no sufficient
evidence that the short-term effect will last for several days
or weeks. Therefore, further controlled clinical studies with
a larger study population are necessary.
Because this was the first study of IR sauna, we had no
idea about the mean group effect in RA or AS patients.
Comparing the changes on prim ary outcome var iables
during treatment with those during the previous nontreat-
ment perio d, we found an improvement of approximately
10% to 15%. So, from power calculations with 80% power
and α of 0.05 for following controlled clinical studies, at
least 25 patients per group are required. Furthermore, it is
recommended to conduct comparable studies in patients
with other types of musculoskeletal disorders such as
osteoarthritis, osteoporosis, and fibromyalgia.
The results of this study show that the use of IR sauna as
treatment is feasible and well tolerated in patients with
inflammatory arthritis.
We would recommend that patients should first experi-
ence a couple of trial sessions to see whether they achieve
any clinical benefit prior to commencing a course of IR.
Based on that experience, continuation of treatment and the
appropriate dose and application can be discussed with the
physician or physiotherapist. Despite the evidence from this
Table 6 Well-being during and after IR sauna
After 15 min After 30 min 30 min after treatment
Number
a
Percentage Number
a
Percentage Number
a
Percentage
RA patients
1 0 0 2 11.8 0 0
2 2 11.8 2 11.8 0 0
3 3 17.6 2 11.8 2 11.8
4 10 58.8 9 52.9 10 58.8
5 2 11.8 2 11.8 5 29.4
AS patients
1 0 0 3 17.6 0 0
2 4 23.5 3 17.6 1 5.9
3 2 11.8 3 17.6 1 5.9
4 9 52.9 2 11.8 9 52.9
5 2 11.8 6 35.3 6 35.3
IR Infrared, RA rheumatoid arthritis, AS ankylosing spondylitis
a
Number of patients; 1 = very uncomfortable, 2 = uncomfortable, 3 = neutral, 4 = comfortable, 5 = very comfortable
Clin Rheumatol (2009) 28:29–34 33
study for positive short-term results and a trend towards
beneficial clinica l l ong- ter m effects, fur ther controlle d
clinical studies are warranted.
Disclosure The study was supported by a non-restricted grant from
the Health Company, Alphen aan de Rijn, The Netherlands, and the
measuring equipment was kindly provided by the Department of
Physiotherapy of Hospital Medisch Spectrum Twente.
Conflict of interest statement None.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
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