Abstract P191: Birth Weight and Risk of Hypertension: A Mendelian Randomization Study of 183433 Individuals from 60 Studies

Abstract

Importance: Epidemiology studies suggested that low birth weight is associated with a higher risk of hypertension in later life. However, little is known about the causality of such associations. Objective: To evaluate the causality of the association between low birth weight and hypertension risk in later life. Design, Setting, and Participants: We collected data from 60 studies with 183,433 participants (CHARGE-BIG consortium), and each study analyzed the data following a standard analytic protocol. We applied a Mendelian randomization analysis using a genetic risk score of low birth weight from seven SNPs as the instrumental variable to explore the possible causal association between birth weight and adulthood hypertension. Main Outcomes and Measures: Hypertension was defined as systolic blood pressure of 140 mmHg or higher, diastolic blood pressure of 90 mmHg or higher, or current use of antihypertensive medication. Results: A total of 70,874 hypertensive participants and 61,933 normotensive controls provided study-level data. In the meta-analysis, each additional risk allele in the risk score was associated with a 0.02 SD decrease in birth weight (p <0.05). Decreased birth weight was associated with a higher risk of hypertension in adults (odds ratio per 1 SD decrease in birth weight: 1.19, 95% confidence interval [CI]: 1.08 to 1.31), while no association was found between a genetic risk score of low birth weight and hypertension risk. The formal Mendelian randomization analysis suggested genetically instrumented birth weight was not associated with risk of hypertension (instrumental odds ratio for causal effect per 1 SD decrease in birth weight: 0.94, 95%CI 0.62 to 1.42). These findings were consistent across different strata of sex, body mass index, or race. Conclusions: Our findings suggest that the association of birth weight with hypertension from observational studies could be the result of confounding.