Differential white blood cell count and epigenetic clocks: a bidirectional Mendelian randomization study

Aug 27, 2024Clinical epigenetics

Two-way genetic study of white blood cell types and biological aging measures

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Abstract

A decrease in lymphocyte count is associated with accelerated aging as measured by multiple , with significant effects noted (P < 0.01).

Lower lymphocyte counts significantly accelerated aging according to PhenoAge, GrimAge, and HannumAge metrics, while not affecting Intrinsic Epigenetic Age Acceleration.
Higher neutrophil counts were linked to increased PhenoAge levels, with a β of 0.38 (95% CI 0.14, 0.61; P = 1.65E-03).
Reverse analyses showed no significant causal effects of epigenetic clocks on overall white blood cell counts.
The impact of lymphocyte counts on epigenetic aging metrics remained statistically significant in multivariate analyses.
Neutrophil counts demonstrated strong causal associations with PhenoAge, GrimAge, and HannumAge, with respective β values of 0.78, 0.55, and 0.42.

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BACKGROUND: Human aging and white blood cell (WBC) count are complex traits influenced by multiple genetic factors. Predictors of chronological age have been developed using . However, the bidirectional causal effects between epigenetic clocks and WBC count have not been fully examined.

METHODS: This study employed (MR) to analyze summary statistics from four epigenetic clocks involving 34,710 participants, alongside data from the Blood Cell Consortium encompassing 563,946 individuals. We primarily explored bidirectional causal relationships using the random-effects inverse-variance weighted method, supplemented by additional MR methods for comprehensive analysis. Additionally, multivariate MR was applied to investigate independent effects of WBC count on epigenetic age acceleration.

RESULTS: In the two-sample univariate MR (UVMR) analysis, we observed that a decrease in lymphocyte count markedly accelerated aging according to the PhenoAge, GrimAge, and HannumAge metrics (all P < 0.01, β < 0), though it did not affect Intrinsic Epigenetic Age Acceleration (IEAA). Conversely, an increase in neutrophil count significantly elevated PhenoAge levels (β: 0.38; 95% CI 0.14, 0.61; P = 1.65E-03 < 0.01). Reverse MR revealed no significant causal impacts of epigenetic clocks on overall WBC counts. Furthermore, in multivariate MR, the impact of lymphocyte counts on epigenetic aging metrics remained statistically significant. We also identified a marked causal association between neutrophil counts and PhenoAge, GrimAge, and HannumAge, with respective results showing strong associations (PhenoAge β: 0.78; 95% CI 0.47, 1.09; P = 8.26E-07; GrimAge β: 0.55; 95% CI 0.31, 0.79; P = 5.50E-06; HannumAge β: 0.42; 95% CI 0.18, 0.67; P = 6.30E-04). Likewise, eosinophil cell count demonstrated significant association with HannumAge (β: 0.33; 95% CI 0.13, 0.53; P = 1.43E-03 < 0.01).

CONCLUSION: These findings demonstrated that within WBCs, lymphocyte and neutrophil counts exert irreversible and independent causal effects on the acceleration of PhenoAge, GrimAge, and HannumAge. Our findings highlight the critical role of WBCs in influencing epigenetic clocks and underscore the importance of considering immune parameters when interpreting epigenetic age.

Key numbers

0.52 years

Increase in GrimAge

Corresponds to a decrease of 1 SD in lymphocyte count.

0.38 years

Increase in PhenoAge

Results from an increase of 1 SD in neutrophil count.

563,946 individuals

Study cohort size

Used for analyzing white blood cell counts.

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Differential white blood cell count and epigenetic clocks: a bidirectional Mendelian randomization study

Abstract

Key numbers

Full Text

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