Skip to main content
Top
Published in: ADHD Attention Deficit and Hyperactivity Disorders 3/2019

01-09-2019 | Review Article

Vitamin D levels in children and adolescents with attention-deficit hyperactivity disorder (ADHD): a meta-analysis

Authors: Evangelia Kotsi, Elisavet Kotsi, Despina N. Perrea

Published in: ADHD Attention Deficit and Hyperactivity Disorders | Issue 3/2019

Login to get access

Abstract

The aim of this article was to assess the differences in serum 25(OH)D levels between children and adolescents with attention-deficit/hyperactivity disorder (ADHD) and healthy controls. We used the PubMed (1966–2017), Scopus (2004–2017), ClinicalTrials.gov (2008–2017), Cochrane Central Register of Controlled Trials CENTRAL (2000–2017), and Google Scholar (2004–2017) databases. Statistical meta-analysis was performed with RevMan 5.3. Εight studies were finally included in the present meta-analysis with a total number of 11,324 children. Among them, 2655 were diagnosed with ADHD, while the remaining 8669 were recruited as healthy controls. All eight trials reported significantly lower serum concentrations of 25(OH)D in patients diagnosed with ADHD compared to healthy controls. The pooled data showed that there was a significant difference between the ADHD group and the control group (SMD = − 0.73, 95% CI [− 1.00, − 0.46]). The systematic review and meta-analysis of observational studies demonstrated an inverse association between serum 25(OH)D and young patients with ADHD. Large cohort studies are required to investigate whether vitamin D-deficient infants are more likely to develop ADHD in the future. Also, whether children with ADHD should be supplemented with higher doses of vitamin D3 remains to be confirmed through long-term controlled clinical trials.
Footnotes
Literature
go back to reference Ascherio A, Munger KL, Simon KC (2010) Vitamin D and multiple sclerosis. Lancet Neurol 9(6):599–612PubMedCrossRef Ascherio A, Munger KL, Simon KC (2010) Vitamin D and multiple sclerosis. Lancet Neurol 9(6):599–612PubMedCrossRef
go back to reference Autier P et al (2014) Vitamin D status and ill health: a systematic review. Lancet Diabetes Endocrinol 2(1):76–89PubMedCrossRef Autier P et al (2014) Vitamin D status and ill health: a systematic review. Lancet Diabetes Endocrinol 2(1):76–89PubMedCrossRef
go back to reference Avcil S et al (2017) Vitamin D deficiency and a blunted parathyroid hormone response in children with attention-deficit/hyperactivity disorder. Clin Lab 63(3):435–443PubMed Avcil S et al (2017) Vitamin D deficiency and a blunted parathyroid hormone response in children with attention-deficit/hyperactivity disorder. Clin Lab 63(3):435–443PubMed
go back to reference Bala KA et al (2016) Hormone disorder and vitamin deficiency in attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs). J Pediatr Endocrinol Metab 29(9):1077–1082PubMedCrossRef Bala KA et al (2016) Hormone disorder and vitamin deficiency in attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs). J Pediatr Endocrinol Metab 29(9):1077–1082PubMedCrossRef
go back to reference Bener A et al (2014) Higher prevalence of iron deficiency as strong predictor of attention deficit hyperactivity disorder in children. Ann Med Health Sci Res 4(Suppl 3):S291–S297PubMedPubMedCentralCrossRef Bener A et al (2014) Higher prevalence of iron deficiency as strong predictor of attention deficit hyperactivity disorder in children. Ann Med Health Sci Res 4(Suppl 3):S291–S297PubMedPubMedCentralCrossRef
go back to reference Berridge MJ (2018) Vitamin D deficiency: infertility and neurodevelopmental diseases (attention deficit hyperactivity disorder, autism, and schizophrenia). Am J Physiol Cell Physiol 314(2):C135–C151PubMedCrossRef Berridge MJ (2018) Vitamin D deficiency: infertility and neurodevelopmental diseases (attention deficit hyperactivity disorder, autism, and schizophrenia). Am J Physiol Cell Physiol 314(2):C135–C151PubMedCrossRef
go back to reference Braegger C et al (2013) Vitamin D in the healthy European paediatric population. J Pediatr Gastroenterol Nutr 56(6):692–701PubMedCrossRef Braegger C et al (2013) Vitamin D in the healthy European paediatric population. J Pediatr Gastroenterol Nutr 56(6):692–701PubMedCrossRef
go back to reference Carvalho JTG et al (2017) Cholecalciferol decreases inflammation and improves vitamin D regulatory enzymes in lymphocytes in the uremic environment: a randomized controlled pilot trial. PLoS ONE 12(6):e0179540PubMedPubMedCentralCrossRef Carvalho JTG et al (2017) Cholecalciferol decreases inflammation and improves vitamin D regulatory enzymes in lymphocytes in the uremic environment: a randomized controlled pilot trial. PLoS ONE 12(6):e0179540PubMedPubMedCentralCrossRef
go back to reference Cass WA, Smith MP, Peters LE (2006) Calcitriol protects against the dopamine- and serotonin-depleting effects of neurotoxic doses of methamphetamine. Ann N Y Acad Sci 1074:261–271PubMedCrossRef Cass WA, Smith MP, Peters LE (2006) Calcitriol protects against the dopamine- and serotonin-depleting effects of neurotoxic doses of methamphetamine. Ann N Y Acad Sci 1074:261–271PubMedCrossRef
go back to reference Childress AC, Sallee FR (2014) Attention-deficit/hyperactivity disorder with inadequate response to stimulants: approaches to management. CNS Drugs 28(2):121–129PubMedCrossRef Childress AC, Sallee FR (2014) Attention-deficit/hyperactivity disorder with inadequate response to stimulants: approaches to management. CNS Drugs 28(2):121–129PubMedCrossRef
go back to reference Coghill D, Hodgkins P (2016) Health-related quality of life of children with attention-deficit/hyperactivity disorder versus children with diabetes and healthy controls. Eur Child Adolesc Psychiatry 25(3):261–271PubMedCrossRef Coghill D, Hodgkins P (2016) Health-related quality of life of children with attention-deficit/hyperactivity disorder versus children with diabetes and healthy controls. Eur Child Adolesc Psychiatry 25(3):261–271PubMedCrossRef
go back to reference Daraki V et al (2018) High maternal vitamin D levels in early pregnancy may protect against behavioral difficulties at preschool age: the Rhea mother–child cohort, Crete, Greece. Eur Child Adolesc Psychiatry 27(1):79–88PubMedCrossRef Daraki V et al (2018) High maternal vitamin D levels in early pregnancy may protect against behavioral difficulties at preschool age: the Rhea mother–child cohort, Crete, Greece. Eur Child Adolesc Psychiatry 27(1):79–88PubMedCrossRef
go back to reference Dawodu A, Nath R (2011) High prevalence of moderately severe vitamin D deficiency in preterm infants. Pediatr Int 53(2):207–210PubMedCrossRef Dawodu A, Nath R (2011) High prevalence of moderately severe vitamin D deficiency in preterm infants. Pediatr Int 53(2):207–210PubMedCrossRef
go back to reference DerSimonian R, Kacker R (2007) Random-effects model for meta-analysis of clinical trials: an update. Contemp Clin Trials 28(2):105–114PubMedCrossRef DerSimonian R, Kacker R (2007) Random-effects model for meta-analysis of clinical trials: an update. Contemp Clin Trials 28(2):105–114PubMedCrossRef
go back to reference Dopfner M et al (2015) Long-term course of ADHD symptoms from childhood to early adulthood in a community sample. Eur Child Adolesc Psychiatry 24(6):665–673PubMedCrossRef Dopfner M et al (2015) Long-term course of ADHD symptoms from childhood to early adulthood in a community sample. Eur Child Adolesc Psychiatry 24(6):665–673PubMedCrossRef
go back to reference Doshi JA et al (2012) Economic impact of childhood and adult attention-deficit/hyperactivity disorder in the United States. J Am Acad Child Adolesc Psychiatry 51(10):990–1002PubMedCrossRef Doshi JA et al (2012) Economic impact of childhood and adult attention-deficit/hyperactivity disorder in the United States. J Am Acad Child Adolesc Psychiatry 51(10):990–1002PubMedCrossRef
go back to reference Eyles DW et al (2009) Developmental vitamin D deficiency causes abnormal brain development. Psychoneuroendocrinology 34(Suppl 1):S247–S257PubMedCrossRef Eyles DW et al (2009) Developmental vitamin D deficiency causes abnormal brain development. Psychoneuroendocrinology 34(Suppl 1):S247–S257PubMedCrossRef
go back to reference Eyles D, Burne T, McGrath J (2011) Vitamin D in fetal brain development. Semin Cell Dev Biol 22(6):629–636PubMedCrossRef Eyles D, Burne T, McGrath J (2011) Vitamin D in fetal brain development. Semin Cell Dev Biol 22(6):629–636PubMedCrossRef
go back to reference Eyles DW, Burne TH, McGrath JJ (2013) Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease. Front Neuroendocrinol 34(1):47–64PubMedCrossRef Eyles DW, Burne TH, McGrath JJ (2013) Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease. Front Neuroendocrinol 34(1):47–64PubMedCrossRef
go back to reference Eyles DW et al (2014) Intracellular distribution of the vitamin D receptor in the brain: comparison with classic target tissues and redistribution with development. Neuroscience 268:1–9PubMedCrossRef Eyles DW et al (2014) Intracellular distribution of the vitamin D receptor in the brain: comparison with classic target tissues and redistribution with development. Neuroscience 268:1–9PubMedCrossRef
go back to reference Feldman HM, Reiff MI (2014) Clinical practice. Attention deficit-hyperactivity disorder in children and adolescents. N Engl J Med 370(9):838–846PubMedCrossRef Feldman HM, Reiff MI (2014) Clinical practice. Attention deficit-hyperactivity disorder in children and adolescents. N Engl J Med 370(9):838–846PubMedCrossRef
go back to reference Gallo EF, Posner J (2016) Moving towards causality in attention-deficit hyperactivity disorder: overview of neural and genetic mechanisms. Lancet Psychiatry 3(6):555–567PubMedPubMedCentralCrossRef Gallo EF, Posner J (2016) Moving towards causality in attention-deficit hyperactivity disorder: overview of neural and genetic mechanisms. Lancet Psychiatry 3(6):555–567PubMedPubMedCentralCrossRef
go back to reference Garipardic M et al (2017) Association of attention deficit hyperactivity disorder and autism spectrum disorders with mean platelet volume and vitamin D. Med Sci Monit 23:1378–1384PubMedPubMedCentralCrossRef Garipardic M et al (2017) Association of attention deficit hyperactivity disorder and autism spectrum disorders with mean platelet volume and vitamin D. Med Sci Monit 23:1378–1384PubMedPubMedCentralCrossRef
go back to reference Goksugur SB et al (2014) Vitamin D status in children with attention-deficit-hyperactivity disorder. Pediatr Int 56(4):515–519PubMedCrossRef Goksugur SB et al (2014) Vitamin D status in children with attention-deficit-hyperactivity disorder. Pediatr Int 56(4):515–519PubMedCrossRef
go back to reference Hawes JE et al (2015) Maternal vitamin D deficiency alters fetal brain development in the BALB/c mouse. Behav Brain Res 286:192–200PubMedCrossRef Hawes JE et al (2015) Maternal vitamin D deficiency alters fetal brain development in the BALB/c mouse. Behav Brain Res 286:192–200PubMedCrossRef
go back to reference Health Quality O (2010) Clinical utility of vitamin d testing: an evidence-based analysis. Ont Health Technol Assess Ser 10(2):1–93 Health Quality O (2010) Clinical utility of vitamin d testing: an evidence-based analysis. Ont Health Technol Assess Ser 10(2):1–93
go back to reference Holick MF (1987) Photosynthesis of vitamin D in the skin: effect of environmental and life-style variables. Fed Proc 46(5):1876–1882PubMed Holick MF (1987) Photosynthesis of vitamin D in the skin: effect of environmental and life-style variables. Fed Proc 46(5):1876–1882PubMed
go back to reference Humble MB, Gustafsson S, Bejerot S (2010) Low serum levels of 25-hydroxyvitamin D (25-OHD) among psychiatric out-patients in Sweden: relations with season, age, ethnic origin and psychiatric diagnosis. J Steroid Biochem Mol Biol 121(1–2):467–470PubMedCrossRef Humble MB, Gustafsson S, Bejerot S (2010) Low serum levels of 25-hydroxyvitamin D (25-OHD) among psychiatric out-patients in Sweden: relations with season, age, ethnic origin and psychiatric diagnosis. J Steroid Biochem Mol Biol 121(1–2):467–470PubMedCrossRef
go back to reference Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Ross AC, Taylor CL, Yaktine AL et al (eds) (2011) Dietary reference intakes for calcium and vitamin D. National Academies Press, Washington Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Ross AC, Taylor CL, Yaktine AL et al (eds) (2011) Dietary reference intakes for calcium and vitamin D. National Academies Press, Washington
go back to reference Kamal M, Bener A, Ehlayel MS (2014) Is high prevalence of vitamin D deficiency a correlate for attention deficit hyperactivity disorder? Atten Defic Hyperact Disord 6(2):73–78PubMedCrossRef Kamal M, Bener A, Ehlayel MS (2014) Is high prevalence of vitamin D deficiency a correlate for attention deficit hyperactivity disorder? Atten Defic Hyperact Disord 6(2):73–78PubMedCrossRef
go back to reference Kaneko I et al (2015) 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D. FASEB J 29(9):4023–4035PubMedCrossRef Kaneko I et al (2015) 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D. FASEB J 29(9):4023–4035PubMedCrossRef
go back to reference Kesby JP et al (2013) Altered dopamine ontogeny in the developmentally vitamin D deficient rat and its relevance to schizophrenia. Front Cell Neurosci 7:111PubMedPubMedCentralCrossRef Kesby JP et al (2013) Altered dopamine ontogeny in the developmentally vitamin D deficient rat and its relevance to schizophrenia. Front Cell Neurosci 7:111PubMedPubMedCentralCrossRef
go back to reference Klein RG et al (2012) Clinical and functional outcome of childhood attention-deficit/hyperactivity disorder 33 years later. Arch Gen Psychiatry 69(12):1295–1303PubMedPubMedCentralCrossRef Klein RG et al (2012) Clinical and functional outcome of childhood attention-deficit/hyperactivity disorder 33 years later. Arch Gen Psychiatry 69(12):1295–1303PubMedPubMedCentralCrossRef
go back to reference Lawrence DW, Sharma B (2016) A review of the neuroprotective role of vitamin D in traumatic brain injury with implications for supplementation post-concussion. Brain Inj 30(8):960–968PubMedCrossRef Lawrence DW, Sharma B (2016) A review of the neuroprotective role of vitamin D in traumatic brain injury with implications for supplementation post-concussion. Brain Inj 30(8):960–968PubMedCrossRef
go back to reference Le HH et al (2014) Economic impact of childhood/adolescent ADHD in a European setting: the Netherlands as a reference case. Eur Child Adolesc Psychiatry 23(7):587–598PubMedCrossRef Le HH et al (2014) Economic impact of childhood/adolescent ADHD in a European setting: the Netherlands as a reference case. Eur Child Adolesc Psychiatry 23(7):587–598PubMedCrossRef
go back to reference Leary PF et al (2017) Effect of Latitude on Vitamin D Levels. J Am Osteopath Assoc 117(7):433–439PubMedCrossRef Leary PF et al (2017) Effect of Latitude on Vitamin D Levels. J Am Osteopath Assoc 117(7):433–439PubMedCrossRef
go back to reference Liberati A et al (2009) The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. J Clin Epidemiol 62(10):e1–e34CrossRefPubMed Liberati A et al (2009) The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. J Clin Epidemiol 62(10):e1–e34CrossRefPubMed
go back to reference Meyer T et al (2017) Attention deficit-hyperactivity disorder is associated with reduced blood pressure and serum vitamin D levels: results from the nationwide German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Eur Child Adolesc Psychiatry 26(2):165–175PubMedCrossRef Meyer T et al (2017) Attention deficit-hyperactivity disorder is associated with reduced blood pressure and serum vitamin D levels: results from the nationwide German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Eur Child Adolesc Psychiatry 26(2):165–175PubMedCrossRef
go back to reference Mohammadpour N et al (2018) Effect of vitamin D supplementation as adjunctive therapy to methylphenidate on ADHD symptoms: a randomized, double blind, placebo-controlled trial. Nutr Neurosci 21(3):202–209PubMedCrossRef Mohammadpour N et al (2018) Effect of vitamin D supplementation as adjunctive therapy to methylphenidate on ADHD symptoms: a randomized, double blind, placebo-controlled trial. Nutr Neurosci 21(3):202–209PubMedCrossRef
go back to reference Morales E et al (2015) Vitamin D in pregnancy and attention deficit hyperactivity disorder-like symptoms in childhood. Epidemiology 26(4):458–465PubMedCrossRef Morales E et al (2015) Vitamin D in pregnancy and attention deficit hyperactivity disorder-like symptoms in childhood. Epidemiology 26(4):458–465PubMedCrossRef
go back to reference Mossin MH et al (2017) Inverse associations between cord vitamin D and attention deficit hyperactivity disorder symptoms: a child cohort study. Aust N Z J Psychiatry 51(7):703–710PubMedCrossRef Mossin MH et al (2017) Inverse associations between cord vitamin D and attention deficit hyperactivity disorder symptoms: a child cohort study. Aust N Z J Psychiatry 51(7):703–710PubMedCrossRef
go back to reference Pludowski P et al (2013) Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality—a review of recent evidence. Autoimmun Rev 12(10):976–989PubMedCrossRef Pludowski P et al (2013) Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality—a review of recent evidence. Autoimmun Rev 12(10):976–989PubMedCrossRef
go back to reference Shang-Guan LL, Zhao YR (2015) Serum levels of 25-hydroxyvitamin D in children with attention deficit hyperactivity disorder. Zhongguo Dang Dai Er Ke Za Zhi 17(8):837–840PubMed Shang-Guan LL, Zhao YR (2015) Serum levels of 25-hydroxyvitamin D in children with attention deficit hyperactivity disorder. Zhongguo Dang Dai Er Ke Za Zhi 17(8):837–840PubMed
go back to reference Sharif MR et al (2015) The relationship between serum vitamin D level and attention deficit hyperactivity disorder. Iran J Child Neurol 9(4):48–53PubMedPubMedCentral Sharif MR et al (2015) The relationship between serum vitamin D level and attention deficit hyperactivity disorder. Iran J Child Neurol 9(4):48–53PubMedPubMedCentral
go back to reference Souza JP, Pileggi C, Cecatti JG (2007) Assessment of funnel plot asymmetry and publication bias in reproductive health meta-analyses: an analytic survey. Reprod Health 4:3PubMedPubMedCentralCrossRef Souza JP, Pileggi C, Cecatti JG (2007) Assessment of funnel plot asymmetry and publication bias in reproductive health meta-analyses: an analytic survey. Reprod Health 4:3PubMedPubMedCentralCrossRef
go back to reference Stang A (2010) Critical evaluation of the Newcastle–Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol 25(9):603–605CrossRef Stang A (2010) Critical evaluation of the Newcastle–Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol 25(9):603–605CrossRef
go back to reference Strom M et al (2014) Vitamin D measured in maternal serum and offspring neurodevelopmental outcomes: a prospective study with long-term follow-up. Ann Nutr Metab 64(3–4):254–261PubMedCrossRef Strom M et al (2014) Vitamin D measured in maternal serum and offspring neurodevelopmental outcomes: a prospective study with long-term follow-up. Ann Nutr Metab 64(3–4):254–261PubMedCrossRef
go back to reference Subcommittee on Attention-Deficit/Hyperactivity Disorder et al (2011) ADHD: clinical practice guideline for the diagnosis, evaluation, and treatment of attention-deficit/hyperactivity disorder in children and adolescents. Pediatrics 128(5):1007–1022CrossRef Subcommittee on Attention-Deficit/Hyperactivity Disorder et al (2011) ADHD: clinical practice guideline for the diagnosis, evaluation, and treatment of attention-deficit/hyperactivity disorder in children and adolescents. Pediatrics 128(5):1007–1022CrossRef
go back to reference Telford C et al (2013) Estimating the costs of ongoing care for adolescents with attention-deficit hyperactivity disorder. Soc Psychiatry Psychiatr Epidemiol 48(2):337–344PubMedCrossRef Telford C et al (2013) Estimating the costs of ongoing care for adolescents with attention-deficit hyperactivity disorder. Soc Psychiatry Psychiatr Epidemiol 48(2):337–344PubMedCrossRef
go back to reference Turner KM et al (2013) Cognitive performance and response inhibition in developmentally vitamin D (DVD)-deficient rats. Behav Brain Res 242:47–53PubMedCrossRef Turner KM et al (2013) Cognitive performance and response inhibition in developmentally vitamin D (DVD)-deficient rats. Behav Brain Res 242:47–53PubMedCrossRef
go back to reference Wallace AM et al (2010) Measurement of 25-hydroxyvitamin D in the clinical laboratory: current procedures, performance characteristics and limitations. Steroids 75(7):477–488PubMedCrossRef Wallace AM et al (2010) Measurement of 25-hydroxyvitamin D in the clinical laboratory: current procedures, performance characteristics and limitations. Steroids 75(7):477–488PubMedCrossRef
go back to reference Wang Y, Zhu J, DeLuca HF (2012) Where is the vitamin D receptor? Arch Biochem Biophys 523(1):123–133PubMedCrossRef Wang Y, Zhu J, DeLuca HF (2012) Where is the vitamin D receptor? Arch Biochem Biophys 523(1):123–133PubMedCrossRef
go back to reference Wang T et al (2016) Serum concentration of 25-hydroxyvitamin D in autism spectrum disorder: a systematic review and meta-analysis. Eur Child Adolesc Psychiatry 25(4):341–350PubMedCrossRef Wang T et al (2016) Serum concentration of 25-hydroxyvitamin D in autism spectrum disorder: a systematic review and meta-analysis. Eur Child Adolesc Psychiatry 25(4):341–350PubMedCrossRef
go back to reference Webb AR, Kline L, Holick MF (1988) Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 67(2):373–378PubMedCrossRef Webb AR, Kline L, Holick MF (1988) Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 67(2):373–378PubMedCrossRef
Metadata
Title
Vitamin D levels in children and adolescents with attention-deficit hyperactivity disorder (ADHD): a meta-analysis
Authors
Evangelia Kotsi
Elisavet Kotsi
Despina N. Perrea
Publication date
01-09-2019
Publisher
Springer Vienna
Published in
ADHD Attention Deficit and Hyperactivity Disorders / Issue 3/2019
Print ISSN: 1866-6116
Electronic ISSN: 1866-6647
DOI
https://doi.org/10.1007/s12402-018-0276-7

Other articles of this Issue 3/2019

ADHD Attention Deficit and Hyperactivity Disorders 3/2019 Go to the issue