TABLE 2.

Summary of effects of continuous positive airway pressure (CPAP) on hormones regulating food intake in obstructive sleep apnoea (OSA) patients

First author [ref.]	Year	Participants	AHI cut-off events·h−1	Sample size	Age years M/F	Baseline BMI kg·m−2 M/F	Baseline ESS M/F	Design	CPAP duration	CPAP compliance h per night M/F	Outcomes	Main findings: effect of CPAP
Leptin
Barcelo [7]	2005	OSA obese	≥20	12	47±9.6#	34.9±3.4#	11±4.9#	Baseline to post-treatment	3 months; 12 months	5.7±1.4	Leptin, a.m., fasted	↓ leptin in nonobese
		OSA nonobese	≥20	14	50±9.8#	25.9±2.0#	13±4.8#
Chin [32]	1999	OSA	>20	21	52.2±3.3	29.3±1.1	N/R	Baseline to post-treatment	3–4 days; 1 month; 6 months	N/R	Leptin, fasted	↓ leptin after 3–4 days, 1 month and 6 months
Chin [50]	2003	OSA	N/R	23	47±12.0¶	31.0±4.0	N/R	Baseline to post-treatment	1 day (n=23); 1 month (n=8)	4.3±1.4	Leptin, a.m., fasted	↓ leptin after 1 day and 1 month
Chihara [17]	2015	OSA	≥20	21	54.6±12.4#	26.5±3.9#	11.1±5.5#	Baseline to post-treatment and between groups	3 months	4.5±2.0	Leptin, a.m., fasted, p.p.	↔ leptin
		Control	<15	15	54.3±14.3	26.2±3.0#	10.4±5.3#
Cuhadaroglu [33]	2009	OSA-CPAP compliant	≥15	31	53.9±9.7+	32.3±4.7	11.3±5.7	Baseline to post-treatment	2 months	>4.0 in all	Leptin, a.m., fasted	↓ leptin
Drummond [57]	2008	OSA	>20	98	53.3±10.7	33.2±5.0	N/R	Baseline to post-treatment	1 week; 6 months	5.8±1.6	Leptin, a.m., fasted	↔ leptin
Garcia [58]	2011	OSA	≥15	20	59.7±8.9	36.5±8.0	14.6±4.5	Baseline to post-treatment	6 months	5.3±0.4	Leptin, a.m., fasted	↔ leptin
Harsch [9]	2003	OSA	≥30	30	52±11.0	32.6±5.5	11±2.2	Baseline to post-treatment and between-group	2 days; 2 months	>3.0	Leptin, a.m., fasted	↓ leptin after 2 months; ↔ control versus treatment
		Control	<5	30	51±5.5	30.6±3.3	5.1±1.6
Harsch [51]	2004	OSA	x̄ = 46	30	56.4± 11.1	32.3±6.5	12.9±3.6	Baseline to post-treatment	2 days; 3 months	5.2±0.9	Leptin, a.m., fasted	↔ leptin at 2 days; ↓ leptin trend (p=0.058) after 3 months
Harsch [54]	2004	OSA	x̄ = 43	40	53.8±11.8	32.8±6.9	12.9±3.6	Baseline to post-treatment	2 days; 3 months	5.2±0.9	Leptin, p.m., fasted	↔ leptin at 2 days; ↓ leptin at 3 months
Hoyos [61]	2012	Active CPAP	≥20	34	51.0±12.3	31.6±5.3	10.0±4.0	Sham-controlled, parallel; RCT	3 months	N/R	Leptin, a.m., fasted	↔ leptin after treatment ↔ leptin between groups
		Sham CPAP	≥20	31	46.4±10.4	31±5.1	10.2±4.8		3 months	N/R
Ip [10]	2000	OSA	≥5	9	43.6±10.1#	27.0±2.9#	N/R	Baseline to post-treatment	6 months	N/R	Leptin, a.m., fasted	↓ leptin at 6 months
Kritikou [60]	2014	OSA	x̄ = 38	35	Range 41.7–66.3	28.6±0.6	10.4±0.9	Sham-controlled, crossover; RCT	2 months	Active: 6.1±1.2 Sham: 5.3±1.2	Leptin, a.m., fasted	↔ leptin at 2 months or between groups
Murri [59]	2009	OSA	≥10	78	52.3±11.3	32.2±5.2	15.3±5.5	Baseline to post-treatment	1 month	N/R	Leptin, a.m., fasted	↔ leptin at 1 month
Saarelainen [55]	1997	OSA	N/R	7	53.6±6.2	34.4±4.9	N/R	Baseline to post-treatment	3 months	5.6	Leptin, a.m., fasted	↓ leptin at 3 months
Sanner [52]	2004	OSA	≥5	68	57.5±11.0§	31.2±5.6§	N/R	Baseline to post-treatment	6 months	5.3±1.4	Leptin, a.m., fasted	↓ leptin at 6 months with effective treatment (AHI <5)
Shimizu [53]	2002	OSA	≥20	21	45.0±11.0	28.9±3.7	N/R	Baseline to post-treatment	1 day	N/R	Leptin, p.m., unfasted, overnight	↓ leptin at 03:00 h and 06:30 h after treatment
Tachikawa [48]	2016	OSA	>20	63	60.6±10.0	27.9±3.8	8.7±5.3	Baseline to post-treatment	1 day; 3 months	4.5±1.6	Leptin, a.m., fasted	↔ leptin after treatment
Takahashi [18]	2008	OSA	x̄ = 46 ¶	14	53.2±8.8	28.5±3.7	N/R	Baseline to post-treatment	3–4 days; 1 month	N/R	Leptin, a.m., fasted	↔ leptin after treatment
Trenell [56]	2007	Regular CPAP	>30ƒ	19	49.0±12.0	36.0±8.0	11.0±5.0	Baseline to post-treatment	3 months	6.0±1.0	Leptin, a.m., fasted	↓ leptin in regular users ↔ leptin in irregular users
		Irregular CPAP	>30ƒ	10	51.0±13.0	32.0±4.0	12.0±6.0			2.0±2.0
Ghrelin
Chihara [17]	2015	OSA	≥20	21	54.6±12.4#	26.5±3.9#	11.1±5.5#	Baseline to post-treatment and between groups	3 months	4.5±2.0	Ghrelin, a.m., fasted, p.p.	↓ fasted, p.p. after treatment; ↔ fasted p.p. in OSA versus control
		Control	<15	15	54.3±14.3	26.2±3.0#	10.4±5.3#
Garcia [58]	2011	OSA	≥15	20	59.7±8.9	36.5±8.0	14.6±4.5	Baseline to post-treatment	6 months	5.3±0.4	Ghrelin, a.m., fasted, p.p.	↓ fasted ghrelin ↔ p.p. ghrelin
Harsch [9]	2003	OSA	≥30	9	54±6.0	33.0±4.2	12.2±2.1	Baseline to post-treatment and between groups	2 days	>3.0	Ghrelin, a.m., fasted	↓ ghrelin after 2 days; ↔ control versus treatment
		Control	<5	9	49±6.0	33.9±3.9	5.1±1.6
Tachikawa [48]	2016	OSA	>20	63	60.6±10.0	27.9±3.8	8.7±5.3	Baseline to post-treatment	1 day; 3 months	4.5±1.6	Ghrelin, a.m., fasted	↔ ghrelin after treatment
Takahashi [18]	2008	OSA	x̄ = 46	21	52.5±8.7	28.8±3.8	N/R	Baseline to post-treatment	3–4 days; 1 month	5.5±1.3	Ghrelin, a.m., fasted	↔ after 3–4 days; ↓ ghrelin after 1 month
Orexin
Busquets [62]	2004	OSA	x̄ = 54	27	52±10.4	31±5.2	10±15.2	Between groups	≥1 year	4.5±0.5	Orexin, 12:00 h	↓ orexin in CPAP versus control
		Control	N/R	13	46±7.2	24±3.6	3±3.6
		OSA-CPAP	x̄ = 8	14	57±11.2	36±3.7	5±3.7
Igarashi [63]	2003	OSA	>20	12	45.3±13.7#	28.6±4.9#	13.2±3.8#	Baseline to post-treatment	3–4 months	N/R	Orexin, a.m., fasted	↓ orexin after treatment
Sakurai [64]	2005	OSA, AI ≥60	≥20	11	50.2±17.2	28.9±5.6	17.1±2.6	Baseline to post-treatment	3–6 months	>4.0 in all	Orexin, a.m., fasted	↑ orexin after treatment ↔ orexin after treatment
		OSA, AI <60	≥20	16	57.5±10.4	26.0±2.8	10.8±2.8
NPY
Barcelo [7]	2005	OSA obese	≥20	12	47±9.6#	34.9±3.4#	11±4.9#	Baseline to	3 months; 12 months	5.7±1.4	NPY, a.m., fasted	↓ NPY in obese and nonobese at 12 months
		OSA nonobese	≥20	14	50±9.8#	25.9±2.0#	13± 4.8#	post-treatment

Data are presented as n or mean±SD, unless otherwise stated. AHI: apnoea–hypopnoea index; M: male; F: female; BMI: body mass index; ESS: Epworth sleepiness scale; NPY: neuropeptide Y; N/R: not reported; p.p.: post-prandial; RCT: randomised controlled trial; AI: arousal index. ↑: significant increase; ↓: significant decrease; ↔: no difference;

^#values represent full OSA group at baseline, not just CPAP;

^¶values represent full CPAP group, not just those with leptin sampling;

⁺values represent full group including compliant and noncompliant CPAP users;

^§values represent full OSA treatment group, not just those treated with CPAP;

^ƒcut-off based on respiratory disturbance index not AHI.