Table 2.

Subgroup analysis of all outcomes based on ALA dosage, duration of supplementation, and combination with inositol

Variable	Number of studies	Effect size SMD	95% CI	I2 (%)	P-value for heterogeneity
BMI
ALA dosage
≤600 mg/day	3	−0.19	−0.54 to 0.16	0	0.450
>600 mg/day	2	0.09	−0.60 to 0.78	74.74	0.050
Combination with inositol
Yes	2	−0.01	−0.92 to 0.90	82.92	0.020
No	3	−0.13	−0.45 to 0.20	0	0.770
FBS
Combination with inositol
Yes	1	−0.39	−0.86 to 0.09	-	-
No	3	−2.62	−5.24 to −0.01a)	97.5	<0.001
HOMA-IR
ALA dosage
≤600 mg/day	3	−2.64	−4.63 to −0.64a)	94.08	<0.001
>600 mg/day	1	−0.26	−0.73 to 0.22	-	-
Combination with inositol
Yes	2	−0.45	−0.89 to −0.01a)	28.33	0.240
No	2	−3.59	−4.35 to −2.82a)	16.83	0.270
Insulin
Duration
≤12 weeks	4	−0.78	−1.82 to 0.27	91.43	<0.001
>12 weeks	3	−2.52	−6.15 to 1.12	98.71	<0.001
ALA dosage
≤600 mg/day	5	−1.99	−4.13 to 0.15	97.72	<0.001
>600 mg/day	2	−0.31	−0.65 to 0.04	0	0.620
Combination with inositol
Yes	2	−0.67	−1.28 to −0.07a)	59.54	0.120
No	5	−1.84	−4.07 to 0.40	98.11	<0.001
E2
ALA dosage
≤600 mg/day	2	0.01	−0.42 to 0.43	0	0.1
>600 mg/day	2	−0.04	−0.38 to 0.30	0	0.940
Combination with inositol
Yes	1	−0.03	−0.50 to 0.44	-	-
No	3	−0.02	−0.35 to 0.31	0	0.980
FSH
ALA dosage
≤600 mg/day	3	−3.69	−5.93 to −1.45a)	92.83	<0.001
>600 mg/day	2	0.07	−0.83 to 0.97	85.05	0.001
Combination with inositol
Yes	1	−0.39	−0.86 to 0.09	-	-
No	4	−2.62	−5.24 to −0.01a)	97.5	<0.001
LH
Duration
≤12 weeks	3	−5.09	−10.05 to −0.13a)	97.58	<0.001
>12 weeks	2	−0.63	−1.61 to 0.34	82.23	0.020
ALA dosage
≤600 mg/day	3	−5.42	−9.73 to −1.11a)	96.55	<0.001
>600 mg/day	2	−0.16	−0.51 to 0.18	0	0.1
Combination with inositol
Yes	1	−0.16	−0.64 to 0.31	-	-
No	4	−4.08	−8.06 to −0.10a)	98.71	<0.001

ALA, alpha-lipoic acid; SMD, standardized mean difference; CI, confidence interval; BMI, body mass index; FBS, fasting blood sugar; HOMA-IR, homeostatic model assessment for insulin resistance; E2, estrogen; FSH, follicle-stimulating hormone; LH, luteinizing hormone.

^a)Statistically significant (P<0.05).