A DNA methylation based measure outperforms circulating CRP as a marker of chronic inflammation and partly reflects the monocytic response to long‐term inflammatory exposure: A Canadian Longitudinal Study on Aging analysis

A key hallmark in the age‐related dysfunction of physiological systems is disruption related to the regulation of inflammation, often resulting in a chronic, low‐grade inflammatory state (i.e., inflammaging). In order to understand the causes of overall system decline, methods to quantify the life‐long exposure or damage related to chronic inflammation are critical. Here, we characterize a comprehensive epigenetic inflammation score (EIS) based on DNA methylation loci (CpGs) that are associated with circulating levels of C‐reactive protein (CRP). In a cohort of 1446 older adults, we show that associations to age and health‐related traits such as smoking history, chronic conditions, and established measures of accelerated aging were stronger for EIS than CRP, while the risk of longitudinal outcomes such as outpatient or inpatient visits and increased frailty were relatively similar. To determine whether variation in EIS actually reflects the cellular response to chronic inflammation we exposed THP1 myelo‐monocytic cells to low levels of inflammatory mediators for 14 days, finding that EIS increased in response to both CRP (p = 0.011) and TNF (p = 0.068). Interestingly, a refined version of EIS based only on those CpGs that changed in vitro was more strongly associated with many of the aforementioned traits as compared to EIS. In conclusion, our study demonstrates that EIS outperforms circulating CRP with regard to its association to health‐traits that are synonymous with chronic inflammation and accelerated aging, and substantiates its potential role as a clinically relevant tool for stratifying patient risk of adverse outcomes prior to treatment or following illness.