Table 2.

Subgroup analyses of the association between insomnia and hypertension.

	No. of reports	OR (95% CI)	Pvalue for heterogeneity	I 2 (%)
Subgroup analyses
Age
<40	1	2.89 (0.76–11.07)	—	—
40–60	14	1.10 (1.05–1.15)	<0.001	85.2
>60	5	1.12 (1.09–1.16)	0.810	0
Sex1
Male (<40%)	6	1.10 (1.03–1.17)	<0.001	81.0
Male (40%–60%)	12	1.12 (1.08–1.15)	0.294	15.4
Male (>60%)	2	1.40 (0.78–2.52)	<0.001	97
Continent
North America	10	1.07 (1.01–1.13)	<0.001	79.1
Asia	3	1.40 (0.94–2.08)	0.011	77.9
Europe	7	1.14 (1.04–1.25)	0.001	72.5
Follow-up time
>5	11	1.06 (1.02–1.10)	<0.001	81.9
≤5	9	1.27 (1.12–1.43)	0.008	55.6
Insomnia subtype2
DIS/DFA	4	1.26 (0.87–1.84)	0.004	77.9
DMS	4	1.17 (0.89–1.55)	0.001	83.0
EMA	2	1.13 (1.07–1.20)	0.566	0
NRS	1	1.39 (0.78–2.48)	—	—
Composite insomnia	15	1.12 (1.06–1.17)	<0.001	79.9
Hypertension assessment
SBP ≥ 140 mmHg and/or DBP ≥ 90 mmHg or use of antihypertensive medication	9	1.21 (1.10–1.33)	<0.001	86.9
Others (self-report or different levels of BP or ICD9/10)	11	1.04 (1.01–1.08)	0.001	66.3
Insomnia assessment
Clinical diagnostic criteria	3	1.03 (0.91–1.17)	0.448	0
Non-clinical insomnia criteria	17	1.12 (1.07–1.17)	<0.001	86.3

CI, confidence interval; OR, odds ratio. HTN, hypertension; BP, blood pressure; EMA: early morning awakening; DMS, difficulty maintaining sleep; DIS; difficulty initiating sleep; DFA; difficulty falling asleep; NRS; non-restorative sleep. ¹The variable “sex” was used as a continuous variable (according to the proportion of males in each study). ²One study provided data on DMS and DIS/DFA. Two studies provided data on DMS, DIS/DFA, and EMA. One study provided data on DIS/DFA and NRS. One study provided data only on DMS. Therefore, there are 26 reports from 20 studies.