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Gaml-Sørensen A, Brix N, Ernst A, Lunddorf LLH, Lindh C, Toft G, Henriksen TB, Arah OA, Ramlau-Hansen CH. The estimated effect of season and vitamin D in the first trimester on pubertal timing in girls and boys: a cohort study and an instrumental variable analysis. Int J Epidemiol 2023; 52:1328-1340. [PMID: 37178177 PMCID: PMC11046010 DOI: 10.1093/ije/dyad060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 04/25/2023] [Indexed: 05/15/2023] Open
Abstract
BACKGROUND Season of birth has been associated with age at menarche. Maternal vitamin D levels in pregnancy may explain this effect. We investigated whether the season of first trimester or maternal 25-hydroxyvitamin D3 [25(OH)D3] levels were associated with pubertal timing in children. METHODS We conducted a follow-up study of 15 819 children born in 2000-03 from the Puberty Cohort, nested in the Danish National Birth Cohort (DNBC). Mean differences in attaining numerous pubertal markers, including a combined estimate for the average age at attaining all pubertal markers, were estimated for low (November-April) relative to high (May-October) sunshine exposure season in the first trimester using multivariable interval-censored regression models. Moreover, we conducted a two-sample instrumental variable analysis using season as an instrument for maternal first-trimester 25(OH)D3 plasma levels obtained from a non-overlapping subset (n = 827) in the DNBC. RESULTS For the combined estimate, girls and boys of mothers who had their first trimester during November-April had earlier pubertal timing than girls and boys of mothers whose first trimester occurred during May-October: -1.0 months (95% CI: -1.7 to -0.3) and -0.7 months (95% CI: -1.4 to -0.1), respectively. In the instrumental variable analysis, girls and boys also had earlier pubertal timing: respectively, -1.3 months (95% CI: -2.1 to -0.4) and -1.0 months (95% CI: -1.8 to -0.2) per SD (22 nmol/L) decrease in 25(OH)D3. CONCLUSIONS Both first pregnancy trimester during November-April and lower 25(OH)D3 were associated with earlier pubertal timing in girls and boys.
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Affiliation(s)
- Anne Gaml-Sørensen
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
- Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), 650 Charles E Young Dr. South, Los Angeles, CA, 90095, USA
| | - Nis Brix
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
- Department of Clinical Genetics, Aarhus University Hospital, Brendstrupgårdsvej 21 C, 8200, Aarhus N, Denmark
| | - Andreas Ernst
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
- Department of Urology, Aarhus University Hospital, Palle Juul-Jensens, Boulevard 35, 8200, Aarhus N, Denmark
| | - Lea Lykke Harrits Lunddorf
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
| | - Christian Lindh
- Division of Occupational and Environmental Medicine, Lund University, Medicon Village, Byggnad 402 A, 22363, Lund, Sweden
| | - Gunnar Toft
- Steno Diabetes Center Aarhus, Aarhus University Hospital, Hedeager 3, 8200, Aarhus N, Denmark
| | - Tine Brink Henriksen
- Perinatal Epidemiology Research Unit, Aarhus University and Department of Paediatrics and Adolescent Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 103, 8200, Aarhus N, Denmark
| | - Onyebuchi A Arah
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
- Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), 650 Charles E Young Dr. South, Los Angeles, CA, 90095, USA
- Department of Statistics, Division of Physical Sciences, UCLA College, Boelter Hall 9434, Los Angeles, CA, 90095, USA
| | - Cecilia Høst Ramlau-Hansen
- Department of Public Health, Research Unit for Epidemiology, Bartholins Allé 2, Aarhus University, 8000, Aarhus C, Denmark
- Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), 650 Charles E Young Dr. South, Los Angeles, CA, 90095, USA
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Brix N, Ernst A, Lauridsen LLB, Parner ET, Arah OA, Olsen J, Henriksen TB, Ramlau-Hansen CH. Childhood overweight and obesity and timing of puberty in boys and girls: cohort and sibling-matched analyses. Int J Epidemiol 2020; 49:834-844. [PMID: 32372073 PMCID: PMC7394964 DOI: 10.1093/ije/dyaa056] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 03/24/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Early puberty is a risk indicator for adult diseases. Identification of modifiable causes of earlier puberty is, therefore, warranted. We estimate the association between childhood body mass index (BMI) and pubertal timing in a cohort study and in a sibling-matched study to adjust for unobserved time-stable confounders shared within families. METHODS For the cohort study, 11 046 of 22 439 (49%) invited children, born 2000-203, from the Danish National Birth Cohort (DNBC) had information on childhood BMI at 7 years and self-reported, half-yearly puberty information from 11 years on Tanner stages, menarche, voice break, first ejaculation, acne, and axillary hair. For the sibling-matched study, 1700 brothers and sisters were included among 86 820 live-born singletons from the DNBC. RESULTS Childhood overweight (85th ≤ BMI < 95th percentile) and obesity (BMI ≥ 95th percentile) were associated with earlier age attaining the pubertal milestones in a dose-dependent manner in boys and girls. When modelling all pubertal milestones simultaneously, the pubertal milestones were attained earlier in: overweight boys: -3.1 [95% confidence interval (CI): -4.5, -1.7] months, overweight girls: -5.5 (95% CI: -7.1, -3.9) months, obese boys: -3.5 (95% CI: -5.1, -2.0) months, obese girls: -5.2 (95% CI: -7.1, -3.4) months compared with normal weight (BMI < 85th percentile) children. In the sibling-matched study, higher BMI was associated with earlier age at attaining most pubertal milestones in girls, but only a tendency toward earlier pubertal timing was observed in boys. CONCLUSIONS Childhood overweight and obesity were associated with earlier pubertal timing even after adjustment for unobserved time-stable confounders shared within families.
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Affiliation(s)
- Nis Brix
- Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Andreas Ernst
- Department of Public Health, Aarhus University, Aarhus, Denmark
| | | | | | - Onyebuchi A Arah
- Department of Epidemiology, Fielding School of Public Health, UCLA, Los Angeles, CA, USA
- Department of Statistics, UCLA College of Letters and Science, Los Angeles, CA, USA
| | - Jørn Olsen
- Department of Epidemiology, Fielding School of Public Health, UCLA, Los Angeles, CA, USA
- Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
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