Table 2.

Sauna studies of rheumatological disease/chronic pain/depression.

Study characteristics			Study sample		Intervention		Comparators		Health effects	Adverse side effects
Author & year	Level of evidence	Design	Pop/country	N	Sauna type	Duration	Comparator/ controls	Outcome measures	Positive/ negative/ negligible	None/mild/ moderate/ severe
2015 Kanji et al. [50]	I	RCT	Chronic tension headache/New Zealand	37	Multiple types, sauna voucher cards	8 weeks	Control group received advice and education	NPRS (numeric pain rating scale), BDI (Beck Depression Inventory), HDI (Headache Disability Index)	Positive, 44% reduction in HA intensity in 6 weeks of treatment arm. Mean change in headache intensity between sauna and control group = 1.27 points (95% CI 0.48–2.07; F = 10.17; df = 1,117; p = 0.002)	None
2005 Masuda et al. [51]	I	RCT	Chronic pain/Japan	46	FIR	4 weeks	Control group received same course of behavioural counselling, CBT, rehabilitation, and exercise therapy	VAS for pain; pain behaviour assessment by researchers with 11-item questionnaire; Zung SDS (self-rating depression scale); anger scoring with CMI (Cornell Medical Index); sleep quality with simple 0–10 scoring; degree of satisfaction of treatments with simple numerical scoring; return to work 2 years after intervention	Positive, increased likelihood of return to work 2 years later (p < 0.05); decrease in anger scoring in sauna group compared to control (4.5 ± 1.1 to 2.2 ± 1.6, p < 0.001)	Moderate, 2 patients excluded -could not tolerate sauna - acute bronchitis and claustrophobia
2005 Masuda et al. [52]	I	RCT	Mild depression/ Japan	28	FIR	4 weeks	Control group received placebo, 45 min bedrest at 24°C and postrest shower in addition to the same rehab programs, physical therapy, occupational therapy	Somatic complaints with CMI (Cornell Medical Index); Zung SDS (self-rating depression scale); VAS for hunger and relaxation; plasma levels of ghrelin, glucose, catechol-amines; daily caloric intake.	Positive, improved somatic complaints (p < 0.001), improved hunger scores (p < 0.0001), and improved relaxation scores (p < 0.0001) in sauna group compared to control group. Plasma ghrelin concentrations and daily caloric intake increased in sauna group (∗t = −2.32, p < 0.05 and ∗t = −2.65, p < 0.05, respectively); ∗t = Student 2-tailed t-test	None
2009 Oosterveld et al. [53]	III	2 single-group (side-by-side) intervention pilot trials	Rheumatoid arthritis (RA) and ankylosing spondylitis (AS)/The Netherlands	34	FIR	4 weeks	No control group; two groups receiving same sauna intervention	VAS, EPM-ROM (Escola Paulista de Medicina range of motion), DUTCH-AIMS (Dutch arthritis impact measurement scales), BASMI (Bath Ankylosing Spondylitis functional index of range of motion), BASDAI (Bath Ankylosing Spondylitis disease activity index); serum ESR	Positive, pain and stiffness decreased in RA (p < 0.05) and AS (p < 0.001) groups during sauna sessions only.	Mild- 12−24% scoring uncomfortable on well-being scores during beginning of sauna
2015 Amano et al. [54]	III	Clinical study with control group, pilot trial	Females with chronic fatigue syndrome/myalgic encephalomyelitis/Japan	15	FIR	8 weeks	6/15 chose not to undergo sauna intervention	SF-36 survey; SRQ-D (brief self-rating questionnaire for depression); STAI (state-trait anxiety inventory questionnaire)	Positive, 7/9 in sauna group improved during sessions; 4/9 were still improved at follow-up 9−40 months afterwards; 2/9 non-responders. 3/6 controls receiving usual treatment improved at follow-up	Moderate- heat intolerance in most participants, protocol changed.
2015 Soejima et al. [55]	III	Single-group clinical study	Chronic fatigue syndrome (CFS)/Japan	10	FIR	4 weeks	No control group	Numerical rating scales for fatigue and POMS (profile of mood states) questionnaire	Positive, decreased fatigue (p = 0.002), improved POMS scores for anxiety (p = 0.008), depression (p = 0.018), fatigue (p = 0.005) and performance status (p = 0.005) after sauna	None
2011 Matsumoto et al. [56]	III	Single-group clinical study	Females with fibromyalgia and autoimmune disorders/Japan	44	FIR	12 weeks	Sauna only one part of intervention; combined with underwater exercise therapy; no control group	VAS-visual analogue scale; no. of tender pts on clinical exam; FIQ (fibromyalgia impact questionnaire); SF-36 quality of life questionnaire	Positive, reduced VAS pain scores (p < 0.001); fewer # of tender pts (p < 0.01); reduced symptoms based upon FIQ (p < 0.001); improved quality of life on SF-36 questionnaire (p < 0.01–0.05) after combined sauna + underwater exercise therapy	None

FIR = Far-infrared sauna; ESR = erythrocyte sedimentation rate; VAS = visual analogue scale; CBT = cognitive behavioural therapy.