From:  Bidirectional relationship between vitamin D deficiency and type 1/type 2 diabetes mellitus: a systematic review and meta-analysis

 The baseline characteristics of the included studies

AuthorsYearStudy periodCountryStudy designPopulationNumber of patientsFollow-up (median/mean)Mean/median ageMale (n)BMI (kg/m2)
On campOff campOn campOff campOn campOff campOn campOff camp
Nóvoa-Medina et al. [11]20232016–2022SpainRetrospectiveT1DM patients age < 15 years146346NA8.4 ± 3.910 ± 2.78314917.3 ± 4.517.6 ± 6.1
Boyraz et al. [29]20162013.10.1–2014.4.30TurkeyRetrospectivePatients with T2DM12662NA58.90 ± 9.43648.016 ± 9.32NANA28.60 ± 3.7126.764 ± 4.317
Khudayar et al. [6]20222020.10–2021.9PakistanRetrospectivePatients with T2DM aged 30 to 60 years525525NA50 ± 5.552.1 ± 5.7284280NANA
Alqudsi et al. [52]20192017.5–2017.9Saudi ArabiaRetrospectiveTeenagers with T1DM aged 12 to 18 years4949NA14.52 ± 2.0613.92 ± 2.032424NANA
Parveen et al. [42]2019NAIndiaRetrospectivePatients with T2DM aged between 19 and 65 years 4444NA45.744.91232626.125.33
Razip et al. [43]20212021.5.21–2021.7.1MalaysiaRetrospectivePatients with T2DM aged 30 to 65 years5050NANANA262828.7 ± 4.8027.3 ± 4.63
Tsur et al. [23]20132008.7–2012.6IsraelProspectivePeople aged 40 to 70 years62,22655,7342 yearsNANANANANANA
Ma et al. [41]20202015.3–2019.5ChinaRetrospectivePatients with T2DM674521NA62.92 ± 2.062.4 ± 3.3319246NANA
Thrailkill et al. [66]2011NAUSARetrospectivePatients with T1DM aged 14 to 40 years11555NA20.8624.3542425.0425.2
Kumar et al. [25]2017NAIndiaRetrospectivePatients with T2DM aged 30 to 70 years7869NA48.50 443333NANA
Yadavelli et al. [68]20232021.1–2022.5IndiaRetrospectiveChildren with T1DM aged 6 to 15 years5050NA11.36NA2138NANA
Lari et al. [39]20222013–2017KuwaitRetrospectivePatients with T2DM203162NA57.329.26605133.5729.03
Daga et al. [30]2012aNAIndiaRetrospectiveNewly diagnosed young patients with T1DM (under 25 years old)1341NA15.1516.986NA16.8117.47
Daga et al. [30]2012bNAIndiaRetrospectiveYoung patients with newly diagnosed diabetes (under 25 years old)5841NA16.9316.9826NA17.2317.47
Salih et al. [47]20212018.2.1–2018.7.30IraqRetrospectivePatients with T2DM who are over 25 years old155155NA49.9448.956870 NANA
Tang et al. [49]20232019.1–2021.1ChinaRetrospectivePatients with T2DM, with or without foot ulcers256100NA55.355.114257NANA
Bae et al. [54]20182011South KoreaRetrospectiveChildren and adolescents aged 6 to 20 years diagnosed with T1DM85518NA14.5 ± 4.413.8 ± 3.837239NANA
Borkar et al. [56]20102007.7–2008.12IndiaRetrospectiveChildren aged 6 to 12 years who are newly diagnosed with T1DM5050NA8.63 ± 2.018.48 ± 1.58293515.74 ± 1.8816.25 ± 2.43
Devaraj et al. [57]2011NAUSARetrospectiveT1DM patients aged 18 years or older5036NA33.5 ± 11.131 ± 11171425.5 ± 5.525 ± 5
Rodrigues et al. [45]20192012.6–2013.9BrazilRetrospectiveT2DM patients aged 32 to 70 years10162NA56 ± 1353 ± 181912NANA
Reddy et al. [44]20152010.10–2013.3IndiaRetrospectivePatients with T2DM16499NANANA9454NANA
Durgarao et al. [32]20172016.12–2017.1IndiaRetrospectiveT2DM patient aged 40 to 60 years100100NA49.76 ± 5.2148.52 ± 6.036366NANA
Jayashri et al. [38]20202012–2013IndiaProspectiveDiabetes patients aged between 20 and 80 years30090010 yearsNANANANANANA
Sarma et al. [48]20182015.8–2016.12IndiaRetrospectivePatients with T2DM4020NA49.65 ± 9.7848.45 ± 8.73NANA24.51 ± 3.1922.26 ± 1.32
Lin et al. [40]2019aNAChinaRetrospectivePatients with T1DM5642NA19.32 ± 4.5920.79 ± 3.292317NANA
Lin et al. [40]2019bNAChinaRetrospectivePatients with T2DM4128NA60.71 ± 16.2654.07 ± 11.042311NANA
Veronese et al. [24]20141995–2009ItalyProspectiveCommunity-dwelling elderly people aged 65 and older without diabetes7251,5024.4 years79.0574.617474827.1427.17
Hassan et al. [36]20242022.3–2022.5SudanRetrospectivePatients with T2DM from Sudan who are 18 years old or older8888NA555540422726
Husemoen et al. [21]20121993–2010.12.31DenmarkProspectiveMen and women aged 41 to 71 years11,42325,43016.4 yearsNANANANANANA
Liu et al. [61]2018NAChinaRetrospectiveChildren and adolescents with T1DM296295NA8.668.4147148NANA
Greer et al. [60]20132007.3–2008.3AustraliaRetrospectiveChildren with T1DM5656NA11.558.672830NANA
Bayani et al. [28]20142011.10–2012.9IranRetrospectivePeople aged 30 to 60 years with T2DM120120NA51.2 ± 7.9850.6 ± 7.735050NANA
Wang et al. [50]20182013.6–2013.7ChinaRetrospectivePatients with T2DM397397NANANANANA26.34 ± 3.6125.45 ± 3.58
Saleem et al. [46]20172017.1.1–2017.8.31PakistanRetrospectivePatients with T2DM100100NA48.55 ± 14.6246.15 ± 12.435351NANA
Majeed et al. [62]20232013.3–2017.4United Arab EmiratesRetrospectiveChildren and adolescents aged 4 to 19 years with T1DM148296NA12.511.966123NANA
Esteghamati et al. [33]20152012.3–2013.8IranRetrospectiveAdults or adolescents aged 15 years and above with T2DM1,195209NA55.8 ± 10.452.5 ± 11.155597 29.7 ± 5.228.5 ± 4.8
Alduraywish et al. [26]20192016.11.1–2017.4.19Saudi ArabiaRetrospectivePatients with T2DM290126NA44.45 ± 16.9647.82 ± 13.29NANA27.66 ± 4.99829.07 ± 4.595
Rochmah et al. [65]20222019.3–2019.5IndonesiaRetrospectiveChildren with T1DM under the age of 183124NA11.22 ± 4.157.55 ± 3.18181017.35 ± 4.3218.54 ± 5.23
Nam et al. [64]2019NASouth KoreaRetrospectivePatients with T1DM under the age of 2096156NA14.7 ± 4.314.0 ± 4.242670.2 ± 0.1–0.1 ± 0.1
Bajaj et al. [27]2014NAIndiaRetrospectivePatients with T2DM aged 8 to 70 years158130NA52.85 ± 8.2651.87 ± 6.439580NANA
Chen et al. [14]20222017–2019ChinaRetrospectiveChildren with T1DM141200NA6.3 ± 3.35.6 ± 3.659114NANA
Bin-Abbas et al. [55]20112010.6–2010.9Saudi ArabiaRetrospectiveSaudi children diagnosed with T1DM for more than 5 months100100NA9.5 ± 3.28.9 ± 2.1414817.6 ± 3.617.9 ± 3.0
Gendy et al. [35]20182016.12–2017.11EgyptRetrospectivePatients with T2DM5050NA52.48 ± 6.5551 ± 8.2101633.03 ± 6.0730.57 ± 7.68
Ahmed et al. [58]20192017.12–2018.11EgyptRetrospectiveChildren with T1DM (before vitamin D treatment)5050NA11.16 ± 3.2710.97 ± 2.77242517.50 ± 3.2417.32 ± 2.92
Fondjo et al. [34]20172015.10–2015.12GhanaRetrospectivePatients with T2DM11898NA58.81 ± 0.9057.79 ± 1.49252226.05 ± 0.4723.73 ± 0.51
Mihçioğlu and Hatun [63]20222009.3.1–2010.9.1TurkeyRetrospectivePatients newly diagnosed with T1DM8030NA8.38 ± 4.258.45 ± 5.39441516.08 ± 2.9018.72 ± 5.68
Ghandchi et al. [59]20122008–2009IranRetrospectivePatients with T1DM aged 5 to 25 years60120NA14.415.15325221.421
Abd-Allah et al. [51]2014NAEgyptRetrospectivePatients with T1DM120120NA11.7 ± 2.811.1 ± 2.6424818.5 ± 4.321.6 ± 1.5
Ziaei-Kajbaf et al. [69]20182015.10–2016.3IranRetrospectiveChildren and teenagers aged 1 to 15 years8585NA8.73 ± 4.057.62 ± 3.68404416.5215.92
Azab et al. [53]20132012.1–2012.12EgyptRetrospectiveChildren and adolescents aged 6 to 16 years with T1DM8040NA11.4 ± 2.510.8 ± 2.3342423.6 ± 5.721.8 ± 4.7
Wierzbicka et al. [67]2016NAPolandRetrospectiveTeenage patients with T1DM6040NA15.1 ± 1.915.6 ± 1.8282021.1 ± 3.121.7 ± 2.9
Pilz et al. [22]20122000–2009NetherlandsProspectivePeople aged 50 to 75 years1061747.5 ± 0.5 yearsNANANANANANA
Fu et al. [5]20242006–2023.3.30UKProspectiveAdults aged 40 to 69 years205,609174,09014.1 years55.5357111,44094,48727.6226.4
Dhas et al. [31]20192016.3–2018.2IndiaRetrospectiveAdults with T2DM aged 30 to 50 years9090-41.83 ± 5.9137.97 ± 6.14505228.46 ± 3.6825.59 ± 3.95
Iqbal et al. [37]20172013.1–2015.7PakistanRetrospectiveAdult patients with T2DM165165-48.8246.2711611628.9625.24
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BMI: body mass index; NA: not available; T1DM: type 1 diabetes mellitus; T2DM: type 2 diabetes mellitus; UK: United Kingdom; USA: United States of America