Study design and analysis characteristics
The search yielded 593 potential reports as shown in Fig. 1. After removal of duplicates, 556 records remained. Initial screening of the title and abstract resulted in the exclusion of 400 references and 156 studies proceeded to detailed evaluation. After further examination, 34 studies met the inclusion criteria and were included in the meta-analysis [8, 20–52].
The basic characteristics of each study were summarized in Table 1. A total of 34 studies including 12711 subjects were included in the present meta-analysis. The present meta-analysis was assessed blood pressure, prevalence of hypertension, TG, HDL-C, nonHDL-C and LDL-C according to BMI categories.
Table 1
Characteristics of included studies in the meta-analysis
Author/year
|
Country
|
Design
|
Participants age (years)
|
PCOS vs. control (n)
|
BMI level (kg/m2)
|
Outcomes
|
Adali (2010)
|
Turkey
|
PC
|
PCOS: 24.73 ± 2.91
Control: 13.04 ± 1.11
|
26 vs. 25
|
PCOS: 24.4 ± 4.23
Control: 23.9 ± 3.95
|
BP, HDL-C, LDL-C, TG
|
Akram (2010)
|
Pakistan
|
RC
|
PCOS: 20–39
Control: 20–39
|
50 vs. 30
|
PCOS: 23.6 ± 0.50
Control: 23.5 ± 0.71
|
HDL-C, LDL-C, TG
|
Alexandraki (2006)
|
Greece
|
PC
|
PCOS: 25.41 ± 0.80
Control: 27.33 ± 0.83
|
27 vs. 27
|
PCOS: 27.42 ± 1.12
Control: 25.05 ± 1.19
|
BP, HDL-C, LDL-C, TG
|
Arikan (2007)
|
Turkey
|
PC
|
PCOS: 22.82 ± 5.53
Control: 24.64 ± 4.22
|
39 vs. 30
|
PCOS: 21.48 ± 6.50
Control: 20.90 ± 6.04
|
HDL-C, LDL-C, TG
|
Berneis (2006)
|
Italy
|
PC
|
PCOS: 25.1 ± 4.2
Control: 25.5 ± 3
|
30 vs. 24
|
PCOS: 28.4 ± 5.8
Control: 28 ± 4.4
|
HDL-C, LDL-C, TG
|
Cascella (2006)
|
Italy
|
PC
|
PCOS: 21.9 ± 2.7
Control: 22.2 ± 2.8
|
50 vs. 50
|
PCOS: 24.6 ± 2.5
Control: 24.4 ± 2.8
|
BP, HDL-C, LDL-C, TG
|
Cetinakalp (2009)
|
Turkey
|
PC
|
PCOS: 24.58 ± 4.61
Control: 25.48 ± 3.38
|
129 vs. 91
|
PCOS: 24.47 ± 4.64
Control: 24.2 ± 3.31
|
HDL-C, LDL-C, TG
|
Cussons (2009)
|
Australia
|
PC
|
PCOS: 30.4 ± 5.54
Control: 34.44 ± 7.8
|
19 vs. 19
|
PCOS: 24.1 ± 2.9
Control: 22.9 ± 3.2
|
BP, HDL-C, LDL-C, TG
|
Diamanti-Kandarakis (2006)
|
Greece
|
PC
|
PCOS: 25.64 ± 0.86
Control: 27.52 ± 1.02
|
25 vs. 25
|
PCOS: 29.08 ± 1.43
Control: 26.22 ± 1.16
|
BP, HDL-C
|
El-Kannishy (2009)
|
Egypt
|
PC
|
PCOS: 25.2 ± 3.6
Control: 24.4 ± 4.07
|
14 vs. 10
|
PCOS: 22.8 ± 2.1
Control: 21.9 ± 2.97
|
HDL-C, LDL-C, TG
|
Erdogan (2007)
|
Turkey
|
PC
|
PCOS: 24.27 ± 5.44
Control: 26.41 ± 5.65
|
68 vs. 26
|
PCOS: 24.41 ± 5.43
Control: 23.35 ± 5.04
|
HDL-C, LDL-C, TG
|
Erdogan (2009)
|
Turkey
|
PC
|
PCOS: 24.07 ± 1.32
Control: 25.01 ± 2.05
|
88 vs. 119
|
PCOS: 24.38 ± 4.13
Control: 23.47 ± 4.12
|
HDL-C, LDL-C, TG
|
Joham (2014)
|
Australia
|
RC
|
28–33
|
183 vs. 4638
|
< 25
|
Prevalence of hypertension
|
Joham (2014)
|
Australia
|
RC
|
28–33
|
117 vs. 1742
|
25.0–29.9
|
Prevalence of hypertension
|
Joham (2014)
|
Australia
|
RC
|
28–33
|
149 vs. 1181
|
≥ 30
|
Prevalence of hypertension
|
Kargili (2010)
|
Turkey
|
RC
|
PCOS: 25.7 ± 5.5
Control: 26.1 ± 5.4
|
168 vs. 52
|
PCOS: 26.8 ± 3.4
Control: 25.4 ± 2.8
|
HDL-C, LDL-C, TG
|
Ketel (2010)
|
Netherland
|
RC
|
PCOS: 28.6 ± 4.5
Control: 27.7 ± 5.3
|
22 vs.14
|
PCOS: 22.0 ± 2.2
Control: 22.2 ± 1.7
|
HDL-C, LDL-C, TG
|
Ketel (2010)
|
Netherland
|
RC
|
PCOS: 30.3 ± 4.2
Control: 28.6 ± 5.3
|
18 vs. 13
|
PCOS: 36.2 ± 5.9
Control: 40.5 ± 7.0
|
HDL-C, LDL-C, TG
|
Legro (2001)
|
USA
|
PC
|
PCOS: 25 ± 6
Control: 29 ± 7
|
42 vs. 27
|
PCOS: 23.1 ± 2.4
Control: 23.0 ± 1.8
|
BP, HDL-C, LDL-C, TG
|
Legro (2001)
|
USA
|
PC
|
PCOS: 28 ± 5
Control: 32 ± 7
|
153 vs. 35
|
PCOS: 37.0 ± 6.9
Control: 37.7 ± 6.4
|
BP, HDL-C, LDL-C, TG
|
Liang (2012)
|
Taiwan
|
PC
|
PCOS: 27 ± 6.4
Control: 29.0 ± 5.1
|
110 vs. 20
|
PCOS: 31.1 ± 3.9
Control: 30.4 ± 3.7
|
Prevalence of hypertension, HDL-C, LDL-C, TG
|
Liang (2012)
|
Taiwan
|
PC
|
PCOS: 26.8 ± 5.1
Control: 28.1 ± 4.2
|
110 vs. 50
|
PCOS: 20.6 ± 2.0
Control: 20.4 ± 2.0
|
Prevalence of hypertension, HDL-C, LDL-C, TG
|
Luque-Ramirez (2007)
|
Spain
|
PC
|
PCOS: 23.0 ± 5.4
Control: 24.8 ± 6.0
|
11 vs. 8
|
PCOS: 22.2 ± 2.0
Control: 21.3 ± 1.3
|
HDL-C, LDL-C, TG
|
Luque-Ramirez (2007)
|
Spain
|
PC
|
PCOS: 23.6 ± 4.6
Control: 29.3 ± 10.3
|
13 vs. 4
|
PCOS: 27.5 ± 1.8
Control: 27.4 ± 1.5
|
HDL-C, LDL-C, TG
|
Luque-Ramirez (2007)
|
Spain
|
PC
|
PCOS: 26.3 ± 6.7
Control: 28.5 ± 5.8
|
16 vs. 8
|
PCOS: 35.8 ± 3.9
Control: 35.5 ± 3.2
|
HDL-C, LDL-C, TG
|
Macut (2008)
|
Serbia
|
PC
|
PCOS: 23.1 ± 5.1
Control: 24.6 ± 4.1
|
75 vs. 51
|
PCOS: 24.9 ± 4.7
Control: 23.7 ± 4.0
|
HDL-C, LDL-C, TG
|
Moran (2009)
|
Australia
|
PC
|
PCOS: 34.1 ± 6.9
Control: 33.8 ± 6.8
|
80 vs. 27
|
PCOS: 36.0 ± 6.6
Control: 37.4 ± 5.6
|
HDL-C, LDL-C, TG
|
Mayer (2005)
|
Australia
|
PC
|
PCOS: 32.7 ± 1.8
Control: 33.2 ± 2.3
|
100 vs. 20
|
PCOS: 37.3 ± 2.43
Control: 36.7 ± 1.28
|
HDL-C, LDL-C, TG
|
Ni (2009)
|
China
|
PC
|
PCOS: 27
Control: 28
|
578 vs. 281
|
PCOS: 21.9
Control: 21.9
|
BP, TG
|
Oral (2008)
|
Turkey
|
PC
|
PCOS: 23.9 ± 3.3
Control: 24.2 ± 3.9
|
48 vs. 43
|
PCOS: 24.1 ± 2.9
Control: 24.0 ± 1.9
|
HDL-C, LDL-C, TG
|
Orio (2004)
|
Italy
|
PC
|
PCOS: 22.2 ± 2.5
Control: 22.6 ± 2.3
|
30 vs. 30
|
PCOS: 22.4 ± 2.1
Control: 22.1 ± 1.8
|
BP, HDL-C, LDL-C, TG
|
Philbois (2018)
|
Brazil
|
PC
|
PCOS: 28.5 ± 5.2
Control: 31.2 ± 6.6
|
30 vs. 30
|
PCOS: 22.9 ± 1.6
Control: 23.5 ± 3
|
BP
|
Rizzo (2011)
|
Italy
|
PC
|
PCOS: 24 ± 5
Control: 24 ± 3
|
350 vs. 90
|
PCOS: 27 ± 7
Control: 27 ± 4
|
HDL-C, LDL-C, TG, nonHDL-C
|
Sasaki (2011)
|
Japan
|
PC
|
PCOS: 30.2 ± 3.9
Control: 31.5 ± 4.4
|
54 vs. 24
|
PCOS: 24.3 ± 5.7
Control: 22.2 ± 3.4
|
BP, HDL-C, LDL-C, TG
|
Shroff (2007)
|
USA
|
PC
|
PCOS: 32 ± 6.5
Control: 36 ± 7.2
|
24 vs. 24
|
PCOS: 36 ± 5.4
Control: 35 ± 3.3
|
Prevalence of hypertension, HDL-C, LDL-C, TG
|
Soares (2009)
|
Brazil
|
PC
|
PCOS: 24.5 ± 3.8
Control: 24.5 ± 5.1
|
40 vs. 50
|
PCOS: 22.7 ± 3.3
Control: 23.1 ± 3.2
|
BP, HDL-C, LDL-C, TG
|
Sterling (2015)
|
Canada
|
RC
|
PCOS: 33
Control: 35
|
71 vs. 323
|
PCOS: 24.6
Control: 23.6
|
Prevalence of hypertension
|
Tarkun (2004)
|
Turkey
|
PC
|
PCOS: 23.45 ± 4.3
Control: 24.4 ± 4.07
|
37 vs. 25
|
PCOS: 23.85 ± 3.26
Control: 22.9 ± 2.97
|
HDL-C, LDL-C, TG
|
Tiras (1999)
|
Turkey
|
PC
|
PCOS: 24.5 ± 6.0
Control: 23.6 ± 3.9
|
35 vs. 35
|
PCOS: 22.9 ± 4.2
Control: 22.0 ± 1.8
|
HDL-C, LDL-C, TG
|
Vryonidou (2005)
|
Greece
|
PC
|
PCOS: 23.9 ± 5.4
Control: 24.7 ± 5.3
|
75 vs. 55
|
PCOS: 27.3 ± 7.0
Control: 26.3 ± 7.7
|
SBP, HDL-C, LDL-C, TG
|
Yildiz (2002)
|
Turkey
|
PC
|
PCOS: 22.9 ± 4.4
Control: 24.8 ± 4.2
|
59 vs. 23
|
PCOS: 23.0 ± 2.4
Control: 22.1 ± 2.2
|
HDL-C, TG
|
PCOS, polycystic ovary syndrome; BMI, body mass index; PC, prospectively cohort study; RC, retrospectively cohort study, BP, blood pressure (including systolic and diastolic blood pressure); SBP, systolic blood pressure; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; TG, triglycerides. |
Risk of bias and quality assessment
The 34 studies included for systematic review were then reviewed with the NOS tool (Table 2). Some studies did not report on allocation concealment. Binding was impossible. One study scored seven out of nine points and one study scored six points, indicating high-quality. Three studies scored four points or less.
Table 2
Assessment of methodological quality (based on Newcastle-Ottawa Scale)
|
Selection (max 4 stars)
|
Comparability (max 2 stars)
|
Exposure (max 3 stars)
|
Overall quality
|
Adali (2010)
|
***
|
**
|
**
|
Good
|
Akram (2010)
|
**
|
**
|
**
|
Fair
|
Alexandraki (2006)
|
***
|
**
|
**
|
Good
|
Arikan (2007)
|
***
|
**
|
**
|
Good
|
Berneis (2006)
|
****
|
**
|
**
|
Good
|
Cascella (2006)
|
****
|
**
|
**
|
Good
|
Cetinakalp (2009)
|
**
|
**
|
**
|
Fair
|
Cussons (2009)
|
**
|
**
|
*
|
Fair
|
Diamanti-Kandarakis (2006)
|
**
|
**
|
*
|
Fair
|
El-Kannishy (2009)
|
****
|
**
|
**
|
Good
|
Erdogan (2007)
|
**
|
*
|
**
|
Fair
|
Erdogan (2009)
|
****
|
**
|
**
|
Good
|
Joham (2014)
|
**
|
**
|
**
|
Fair
|
Kargili (2010)
|
**
|
**
|
**
|
Fair
|
Ketel (2010)
|
****
|
**
|
**
|
Good
|
Legro (2001)
|
***
|
*
|
**
|
Good
|
Liang (2012)
|
***
|
*
|
**
|
Good
|
Luque-Ramirez (2007)
|
***
|
**
|
**
|
Good
|
Macut (2008)
|
**
|
**
|
**
|
Fair
|
Moran (2009)
|
***
|
**
|
**
|
Good
|
Mayer (2005)
|
****
|
**
|
**
|
Good
|
Ni (2009)
|
**
|
*
|
**
|
Fair
|
Oral (2008)
|
**
|
*
|
**
|
Fair
|
Orio (2004)
|
***
|
**
|
**
|
Good
|
Philbois (2018)
|
**
|
**
|
**
|
Fair
|
Rizzo (2011)
|
**
|
**
|
**
|
Fair
|
Sasaki (2011)
|
***
|
**
|
**
|
Good
|
Shroff (2007)
|
***
|
**
|
**
|
Good
|
Soares (2009)
|
**
|
**
|
**
|
Fair
|
Sterling (2015)
|
**
|
*
|
**
|
Fair
|
Tarkun (2004)
|
**
|
**
|
**
|
Fair
|
Tiras (1999)
|
**
|
**
|
**
|
Fair
|
Vryonidou (2005)
|
****
|
**
|
**
|
Good
|
Yildiz (2002)
|
**
|
*
|
**
|
Fair
|
SELECTION |
(1) Is the case definition adequate? (a) yes, with independent validation*, (b) yes, e.g. record linkage or based on self-reports, (c) no description |
(2) Representativeness of the cases: (a) consecutive or obviously representative series of cases*, (b) potential for selection biases or not stated |
(3) Selection of controls: (a) community controls*, (b) hospital controls, (c) no description |
(4) Definition of controls: (a) no history of disease (end-point)*, (b) no description of source |
COMPARABILITY |
Comparability of cases and controls on basis of design or analysis: (a) study controls for ___ (most important factor)*, (b) study controls for any additional factor* (could be modified to indicate specific control for a second factor) |
EXPOSURE |
(1) Ascertainment of exposure: (a) secure record (e.g. surgical record)*, (b) structured interview where blind to case/control status*, (c) interview not blinded to case/control status, (d) written self-report or medical record only, (e) no description. |
(2) Same method of ascertainment for cases and controls: (a) yes*, (b) no. |
(3) Non-response rate: (a) same rate for both groups*, (b) non-respondents describe, (c) rate different and no designation. |
OVERALL QUALITY |
Good quality: 3 or 4 stars in selection domain AND 1 or 2 stars in comparability domain AND 2 or 3 stars in exposure domain. |
Fair quality: 2 stars in selection domain AND 1 or 2 stars in comparability domain AND 2 or 3 stars in exposure domain. |
Poor quality: 0 or 1 star in selection domain OR 0 star in comparability domain OR 0 or 1 star in exposure domain. |
Blood pressure
Figures 2–4 are forest plots summarizing comparison of SBP, DBP and prevalence of hypertension, respectively. Because the aim was assessed the effect of BMI categories on cardiovascular risk in reproductive women with PCOS, we analyzed the outcomes based on BMI categories.
As shown in Figs. 2 and 3, SBP [MD (95% CI): 2.96 mmHg (1.62, 4.30), P < 0.001] and DBP [MD (95% CI): 1.64 mmHg (0.03, 3.24), P = 0.046] increased in reproductive-aged women with PCOS. In the subgroup analysis of SBP, BMI of < 25 kg/m2 [MD (95% CI): 3.02 mmHg (1.11, 4.94), P < 0.002] and BMI of ≥ 30 kg/m2 [MD (95% CI): 4.27 mmHg (0.50, 8.04), P < 0.026] showed significant results, while BMI of 25-< 30 kg/m2 [MD (95% CI): 1.56 mmHg (-0.60, 3.71), P = 0.157] did not show positive result. However, in the subgroup analysis, DBP did not increase in BMI of < 25 kg/m2 [MD (95% CI): 1.75 mmHg (-0.23, 3.75), P = 0.083], BMI of ≥ 30 kg/m2 [MD (95% CI): -0.24 mmHg (-3.16, 2.69), P = 0.873], and BMI of 25-< 30 kg/m2 [MD (95% CI): 3.13 mmHg (-0.98, 7.24), P = 0.136].
As shown in Fig. 4, prevalence of hypertension had non-significant difference in reproductive-aged women with PCOS [OR (95% CI): 1.56 (0.76, 3.06), P = 0.198]. Besides, there was no significant difference in BMI of < 25 kg/m2 [OR (95% CI): 1.33 (0.12, 15.14), P = 0.819], BMI of ≥ 30 kg/m2 [OR (95% CI): 1.53 (0.90, 2.61), P = 0.116], and BMI of 25-< 30 kg/m2 [OR (95% CI): 1.85 (0.80, 4.28), P = 0.153].
Lipid profiles
Figure 5-8 are forest plots summarizing comparison of HDL-C, TG, nonHDL-C and LDL-C, respectively. As shown in Figure 5 and 6, reproductive-aged women with PCOS had significantly difference on HDL-C [SMD (95% CI): -0.24 (-0.39, -0.09), P = 0.002] and TG [SMD (95% CI): 0.37 (0.26, 0.48), P < 0.001]. The subgroup analysis of TG, BMI of < 25 kg/m2 [SMD (95% CI): 0.34 (0.20, 0.49), P < 0.001], BMI of ≥ 30 kg/m2 [MD (95% CI): 0.54 (0.31, 0.78), P < 0.001], and BMI of 25-< 30 kg/m2 [MD (95% CI): 0.25 (0.06, 0.43), P = 0.008] were increased in reproductive-aged women with PCOS. Meanwhile, the subgroup analysis showed that HDL-C significantly increased in BMI of < 25 kg/m2 [SMD (95% CI): -0.30 (-0.50, -0.11), P = 0.002], and BMI of 25-< 30 kg/m2 [MD (95% CI): -0.33 (-0.65, -0.01), P = 0.041]. However, BMI of ≥ 30 kg/m2 had no significant difference [MD (95% CI): 0.07 (-0.26, 0.40), P = 0.664].
Figure 7 and 8 are forest plots summarizing comparison of nonHDL-C and LDL-C, respectively. As shown in Figure 7 and 8, reproductive-aged women with PCOS had significant difference on nonHDL-C [SMD (95% CI): 0.38 (0.29, 0.47), P < 0.001] and LDL-C [SMD (95% CI): 0.25 (0.17, 0.34), P < 0.001]. The subgroup analysis showed that nonHDL-C increased in BMI of < 25 kg/m2 [SMD (95% CI): 0.37 (0.24, 0.50), P < 0.001], BMI of ≥ 30 kg/m2 [MD (95% CI): 0.49 (0.30, 0.69), P < 0.001], and BMI of 25-< 30 kg/m2 [MD (95% CI): 0.33 (0.24, 0.50), P < 0.001]. In addition, LDL-C increased in BMI of < 25 kg/m2 [SMD (95% CI): 0.28 (0.15, 0.41), P < 0.001] and BMI of ≥ 30 kg/m2 [MD (95% CI): 0.25 (0.06, 0.44), P = 0.010]. However, LDL-C did not increase in BMI of 25-< 30 kg/m2 [MD (95% CI): 0.19 (-0.01, 0.39), P = 0.066].
Publication bias
There was no publication bias for SBP (asymmetry test P = 0.510), DBP (asymmetry test P = 0.092), HDL (asymmetry test P = 0.405), TG (asymmetry test P = 0.633), nonHDL-C (asymmetry test P = 0.938), and LDL (asymmetry test P = 0.628) according to the results of Egger’s regression test.