Why carry out this study?
|
Alopecia areata (AA) is a form of non-scarring hair loss characterized by an autoimmune reaction to hair follicles with disordered, shortened hair cycle |
Vitamin D deficiency was considered as a risk factor for the development of AA |
The relationship between vitamin D deficiency and AA in patients was reported in two previous meta-analyses but not comprehensively evaluated because five subsequent studies were not considered |
What was learned from the study?
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Deficiency of serum 25(OH)D level, rather than calcium level, was present in patients with AA. Screening for vitamin D deficiency and vitamin D supplementation may be beneficial in treatment of patients with AA |
Introduction
Methods
Search Strategy
Selection Criteria
Data Extraction and Assessment of Risk of Bias
Outcomes
Statistical Analysis
Results
Characteristics of Included Studies
Study | Study design | Sample size | Age (year, mean or median) | Male (%) | Country/Race | Control setting | Outcome of interest | ||||
---|---|---|---|---|---|---|---|---|---|---|---|
Total | AA | Control | AA | Control | AA | Control | |||||
Marahatta S, 2019 | Case-control study | 60 | 30 | 30 | 28.37+10.070 | 30.50 + 9.032 | 16 (51.6%) | 15 (48.4%) | Nepal | Age- and sex-matched healthy controls from hospital staffs | Vitamin D level, Vitamin D deficiency |
Rehman F, 2019 | Case-control study | 270 | 135 | 135 | 26 ± 12.89 | 26 ± 13.20 | 91 (67.41%) | 91 (67.41%) | India | Age- and sex-matched healthy controls | Vitamin D level, Vitamin D deficiency, serum calcium level |
Siddappa H, 2019 | Case-control study | 200 | 100 | 100 | 24.52 ± 10.06 | 28.96±11.49 | 72 (72%) | 58 (58%) | India | Age- and sex-matched healthy controls without any history of alopecia areata or other autoimmune/systemic diseases | Vitamin D level, Vitamin D deficiency |
Daroach M, 2018 | Case-control study | 60 | 30 | 30 | 28.9 ± 9.96 | 31.17 ± 9.43 | 11 (36.67%) | 16 (53.33%) | India | Age- and sex-matched healthy controls | Vitamin D level, Vitamin D deficiency |
Gade V.K.V., 2018 | Case-control study | 90 | 45 | 45 | 32.73 ± 10.43 | 33.98 ± 8.48 | 14 (31.1%) | 14 (31.1%) | India | Age- and sex-matched healthy volunteers | Vitamin D level, serum calcium level |
Unal M, 2018 | Case-control study | 54 | 20 | 34 | 12.4 ± 4.2 | 16.6 ± 0.8 | 14 (70%) | 15 (44.12%) | Turkey | Pediatric healthy controls recruited from individuals who visited to the outpatient clinic | Vitamin D level |
Bhat Y.J., 2017 | Cross-sectional study | 85 | 50 | 35 | 22.4 ± 8.6 | 29.2 ± 7.6 | NR | NR | India | Age- and sex-matched individuals selected randomly from outpatient department with no history of AA | Vitamin D level, serum calcium level |
Conic R.Z., 2017 | Case-control study | 756 | 584 | 172 | 35.54 ± 19.28 | 35.80 ± 15.56 | 184 (31.50%) | 46 (26.75%) | USA | Age-matched patients given a diagnosis of seborrheic dermatitis without hair loss was randomly selected | Vitamin D deficiency |
Darwish NMM, 2017 | Case-control study | 50 | 30 | 20 | 28.67 ± 10 | 24.8 ± 6 | 13 (43.3%) | 10 (50%) | Egypt | Age- and sex matched healthy controls | Vitamin D level, serum calcium level |
Erpolat S, 2017 | Case-control study | 73 | 41 | 32 | 32.8 ± 7.5 | 32.7 ± 7.5 | 26 (63.4%) | 18 (56.3%) | Turkey | Healthy control | Vitamin D level, Vitamin D deficiency, serum calcium level |
Ghafoor R, 2017 | Case-control study | 60 | 30 | 30 | 23.77 ± 8.86 | 24.03 ± 8.62 | 12 (40%) | 12 (40%) | Pakistan | Healthy volunteers and patients coming to dermatology department for other disorders like acne, melasma, etc. | Vitamin D level |
Attawa E, 2016 | Cross-sectional study | 46 | 23 | 23 | 26.44 ± 10.87 | 29.39 ± 8.10 | 15 (65.2%) | 14 (60.9%) | Egypt | Healthy controls | Vitamin D level, Vitamin D deficiency |
Bakry O.A., 2016 | Case-control study | 120 | 60 | 60 | 20.7 ± 10.85 | 23.71 ± 7.45 | 36 (60%) | 28 (46.7%) | Egypt | Age, gender, skin phototype, and body mass index-matched healthy subjects | Vitamin D level, Vitamin D deficiency |
Fattah N.S.A.A., 2015 | Case-control study | 60 | 30 | 30 | 26.8 ± 6.9 | 25.1 ± 6.9 | 18 (60%) | 18 (60%) | Egypt | Healthy volunteers, matched for age, sex, Fitzpatrick skin phototype, the approximate daily amount of vitamin D intake from food source, the occupation (indoor or outdoor), and time of blood sampling | Vitamin D level, Vitamin D deficiency |
Aksu Cerman A, 2014 | Cross-sectional study | 144 | 86 | 58 | 32.21 ± 9.60 | 32.55 ± 9.78 | 56 (47.9%) | 34 (29.1%) | Turkey | Age- and sex-matched volunteers from the hospital staff. | Vitamin D level, Vitamin D deficiency |
Mahamid M, 2014 | Case-control study | 43 | 23 | 20 | 24.2 ± 12.3 | 27 ± 11.26 | 14 (60.87%) | 13 (65%) | Israel | Individuals without a history of AA who were enrolled randomly from clinics | Vitamin D level, Vitamin D deficiency |
d’Ovidio R, 2013 | Case-control study | 304 | 156 | 148 | 37.8 | 34.5 | 45 (28.85%) | 18 (12.16%) | Italy | Healthy individuals | Vitamin D deficiency |
El-Mongy NN, 2013 | Case-control study | 140 | 70 | 70 | 27.79 ± 9.116 | 30.49 ± 11.059 | 37 (52.9%) | 44 (62.9%) | Egypt | Normal controls | Vitamin D level, Vitamin D deficiency |
Yilmaz N, 2012 | Case-control study | 84 | 42 | 42 | 30.8 ± 8.2 | 29.3 ± 7.4 | 14 (33.33%) | 13 (30.95) | Turkey | Healthy individuals | Vitamin D level, serum calcium level |
Heterogeneity and Publication Bias
Meta-analysis Results
Subgroup Analysis
Vitamin D | Vitamin D deficiency | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
No. of articles | WMD (95%CI) | p | I2 (%) | pheterogeneity | No. of articles | OR (95% CI) | p | I2 (%) | pheterogeneity | |
Overall | 17 | − 9.08 (− 11.66, − 6.50) | < 0.001 | 87.90 | < 0.001 | 13 | 4.14 (2.34, 7.35) | < 0.001 | 81.10 | < 0.001 |
Design | ||||||||||
Case–control | 14 | − 9.05 (− 12.46, − 5.63) | < 0.001 | 89.70 | < 0.001 | 11 | 3.66 (2.06, 6.49) | < 0.001 | 78.80 | < 0.001 |
Cross-sectional | 3 | − 9.82 (− 11.91, − 7.72) | < 0.001 | 40.20 | 0.188 | 2 | 6.65 (0.65, 68.27) | 0.111 | 84.90 | 0.01 |
Sample size | ||||||||||
≤ 100 | 12 | − 9.59 (− 13.44, − 5.74) | < 0.001 | 90.50 | < 0.001 | 6 | 5.36 (1.29, 22.21) | 0.021 | 76.50 | 0.001 |
> 100 | 5 | − 8.35 (− 11.19, − 5.51) | < 0.001 | 75.50 | < 0.001 | 7 | 3.94 (2.06, 7.54) | < 0.001 | 85.70 | < 0.001 |
Controls | ||||||||||
Matched | 12 | − 11.38 (− 13.99, − 8.78) | < 0.001 | 84.60 | < 0.001 | 9 | 6.96 (3.54, 13.68) | < 0.001 | 80.80 | < 0.001 |
Not matched | 5 | − 3.18 (− 8.35, 1.99) | 0.228 | 84.10 | < 0.001 | 4 | 1.52 (1.00, 2.32) | 0.052 | 1.10 | 0.386 |
Male ratio | ||||||||||
> 1/2 | 11 | − 7.79 (− 11.47, − 4.11) | < 0.001 | 88.60 | < 0.001 | 10 | 4.51 (2.05, 9.93) | < 0.001 | 83.10 | < 0.001 |
≤ 1/2 | 5 | − 12.03 (− 16.93, − 7.13) | < 0.001 | 86.00 | < 0.001 | 3 | 3.24 (1.37, 7.63) | 0.007 | 0.3767 | 0.012 |
NR | 1 | − 8.89 (− 10.56, − 7.22) | < 0.001 | |||||||
Mean age (years) | ||||||||||
> 25 | 14 | − 10.06 (− 12.87, − 7.24) | < 0.001 | 87.50 | < 0.001 | 12 | 3.58 (2.04, 6.28) | < 0.001 | 78.30 | < 0.001 |
≤ 25 | 3 | − 4.49 (− 13.24, 4.25) | 0.314 | 91.40 | < 0.001 | 1 | 16.43 (6.65, 40.61) | < 0.001 | ||
Country | ||||||||||
Nepal | 1 | − 9.68 (− 19.62, 0.26) | 0.056 | 1 | 4.38 (1.32, 14.50) | 0.016 | ||||
India | 5 | − 8.73 (− 11.59, − 5.87) | < 0.001 | 81.80 | < 0.001 | 3 | 2.55 (1.54, 4.21) | < 0.001 | 29.10 | 0.244 |
Turkey | 4 | − 3.37 (− 10.68, 3.94) | 0.366 | 94.0 | < 0.001 | 2 | 2.97 (0.06, 147.87) | 0.585 | 94.1 | < 0.001 |
Egypt | 5 | − 14.75 (− 22.10, − 7.39) | < 0.001 | 90.60 | < 0.001 | 4 | 8.91 (1.20, 66.39) | 0.033 | 86.9 | < 0.001 |
Pakistan | 1 | − 9 (− 15.55, − 2.45) | 0.007 | |||||||
Israel | 1 | − 10.23 (− 17.51, − 2.95) | 0.006 | 1 | 6.86 (1.78, 26.36) | 0.005 | ||||
Italy | 1 | 1.73 (1.08, 2.79) | 0.023 | |||||||
USA | 1 | 4.37 (2.71, 7.04) | < 0.001 |