Table 1.

Study characteristics of included studies.

Study ID	Authors	Country	Study designs	Study period	Case	Sample size (case/control)	Age (case/control) in years	BMI (case/control)	Adjusted variable
Doi: 10.1378/chest.07-117	Goncalves et al. (19)	Brazil	Case control	March 2004–June 2006	Hospital-based R-HTN	63/63	59 ± 7/59 ± 7	30 ± 3/29 ± 4	Age, gender, BMI, hypertension duration
Doi: 10.1097/HJH.0b013e328351d08a	Abdel-Kader et al. (30)	NR	Cohort study	March 2004- December 2008	Community-based R-HTN	224	60 ± 7.2	29.5 ± 5.0	Age, gender, Race, BMI
Doi: 10.1016/j.ijcard.2017.10.089	Cai et al. (31)	China	Cohort study	February 2015–september 2016	Hospital-based R-HTN	1157	56.6 ± 11.7	24.4 ± 4.7	Age, Gender, Neck Girth, BMI,
Doi: 10.1097/HJH.0b013e32832af679	Ruttanaumpawan et al. (32)	Canada	Cohort study	NR	Hospital-based R-HTN	42/22	56.5 ± 1.6/60.1 ± 1.8	33.7 ± 0.9/32.9 ± 1.0	Age, sex and BMI
Doi: 10.5664/jcsm.3946	Walia et al. (7)	US	RCT	February 2010–august 2012	Hospital based OSA	28/175	65.2 ± 6.5/62.5 ± 7.4	36.3 ± 5.3/33.9 ± 5.4	Age, sex, race, body mass index, smoking status
Doi: 10.3109/10641963.2016.1151525	Wu et al. (33)	South China	Cohort study	April 2008–August 2012	Hospital based OSA	216/452	54.3 ± 3.0	28.07 ± 3.72	Gender, age, BMI, and duration Of hypertension
Doi: 10.1016/j.amjcard.2009.12.017	Drager et al. (34)	Brazil	Cohort study	January 2009–July 2009	Hospital based OSA	55/44	51 ± 10/40 ± 10	30.95 ± 1.80/26.95 ± 1.69	Age, gender, BMI

ABPM, ambulatory BP monitoring.