Dataset Information

Mendelian randomization suggests that head circumference, but not birth weight and length, associates with intelligence.

ABSTRACT:

Introduction

Birth parameters have long been reported to have a role in human intelligence. However, the causalities reported in previous observational studies were controversial. Our study aims to provide an unbiased investigation of the causal associations between birth parameters and human intelligence using the Mendelian randomization (MR) approach.

Methods

Genetic instrumental variables for MR analyses were extracted from large genome-wide association studies of infant head circumference (N = 10,768), birth length (N = 28,489), and birth weight (N = 321,223). Data for intelligence were obtained from a meta-analysis of genome-wide association studies of 269,867 individuals of the European ancestry. Primary MR analysis was performed using the standard inverse-variance weighted method, and sensitivity analyses were performed using the weighted median, MR-Egger, and MR-PRESSO methods.

Results

Using 10 single nucleotide polymorphisms as instrumental variables, we found that 1 standard deviation increase in infant head circumference was associated with 0.14-fold higher scores in intelligence tests (β = 0.14, 95% confidence interval: 0.09 to 0.18, P_IVW =2.05 × 10^-9 ). The causal relationship was robust when sensitivity analyses were performed. However, birth length and birth weight had no significant associations with intelligence.

Conclusion

Our findings suggested infant head circumference, but not birth weight and length were associated with intelligence, which might indicate that brain development rather than general fetal growth was responsible for the development of intelligence.

SUBMITTER: Qian L

PROVIDER: S-EPMC8213647 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature

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Publications

Mendelian randomization suggests that head circumference, but not birth weight and length, associates with intelligence.

Qian Li L Gao Fengjie F Yan Bin B Yang Lihong L Wang Wei W Bai Ling L Ma Xiancang X Yang Jian J

Brain and behavior 20210510 6

<h4>Introduction</h4>Birth parameters have long been reported to have a role in human intelligence. However, the causalities reported in previous observational studies were controversial. Our study aims to provide an unbiased investigation of the causal associations between birth parameters and human intelligence using the Mendelian randomization (MR) approach.<h4>Methods</h4>Genetic instrumental variables for MR analyses were extracted from large genome-wide association studies of infant head c ...[more]

PMID: 33969932

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Project description:ImportanceObservational studies have shown associations of birth weight with type 2 diabetes (T2D) and glycemic traits, but it remains unclear whether these associations represent causal associations.ObjectiveTo test the association of birth weight with T2D and glycemic traits using a mendelian randomization analysis.Design, setting, and participantsThis mendelian randomization study used a genetic risk score for birth weight that was constructed with 7 genome-wide significant single-nucleotide polymorphisms. The associations of this score with birth weight and T2D were tested in a mendelian randomization analysis using study-level data. The association of birth weight with T2D was tested using both study-level data (7 single-nucleotide polymorphisms were used as an instrumental variable) and summary-level data from the consortia (43 single-nucleotide polymorphisms were used as an instrumental variable). Data from 180 056 participants from 49 studies were included.Main outcomes and measuresType 2 diabetes and glycemic traits.ResultsThis mendelian randomization analysis included 49 studies with 41 155 patients with T2D and 80 008 control participants from study-level data and 34 840 patients with T2D and 114 981 control participants from summary-level data. Study-level data showed that a 1-SD decrease in birth weight due to the genetic risk score was associated with higher risk of T2D among all participants (odds ratio [OR], 2.10; 95% CI, 1.69-2.61; P = 4.03 × 10-5), among European participants (OR, 1.96; 95% CI, 1.42-2.71; P = .04), and among East Asian participants (OR, 1.39; 95% CI, 1.18-1.62; P = .04). Similar results were observed from summary-level analyses. In addition, each 1-SD lower birth weight was associated with 0.189 SD higher fasting glucose concentration (β = 0.189; SE = 0.060; P = .002), but not with fasting insulin, 2-hour glucose, or hemoglobin A1c concentration.Conclusions and relevanceIn this study, a genetic predisposition to lower birth weight was associated with increased risk of T2D and higher fasting glucose concentration, suggesting genetic effects on retarded fetal growth and increased diabetes risk that either are independent of each other or operate through alterations of integrated biological mechanisms.

Dataset Information

Mendelian randomization suggests that head circumference, but not birth weight and length, associates with intelligence.

Introduction

Methods

Results

Conclusion

Publications

Mendelian randomization suggests that head circumference, but not birth weight and length, associates with intelligence.

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