BACKGROUND:
The relationship between levels of extracellular matrix (ECM) turnover and mortality is currently unknown. The study aimed to determine if levels of ECM turnover are predictors of all-cause mortality in a large cohort of post-menopausal women.

METHODS:
5,855 postmenopausal Danish women enrolled in the Prospective Epidemiologic Risk Factor (PERF) study. Baseline demographics and serum were collected at registration. Dates of death were obtained from the Danish Death Registry. ECM turnover was evaluated by serological biomarkers measuring bone (telopeptide of type I collagen (CTX-1) and osteocalcin) and soft tissue (formation of type VI collagen (PRO-C6), MMP-degraded type IV collagen (C4M), formation of type III collagen (PRO-C3) and MMP-degraded type I collagen (C1M)) turnover. Multivariate Cox analyses were performed with 3, 5 and 15 years of follow-up.

RESULTS:
The association of bone turnover (CTX-1 and osteocalcin) with all-cause mortality was U-shaped for all time periods. After adjustment for possible confounders, the lowest quintile of bone formation and degradation remained significant for all time periods. We observed J-shaped association between all-cause mortality and PRO-C6, C4M and PRO-C3, and there was a linear association between C1M and all-cause mortality. After adjustment for possible confounders, the highest quintile of the soft tissue turnover biomarkers (PRO-C6, C4M, PRO-C3 and C1M) remained significantly associated with all-cause mortality for all time periods.

CONCLUSION:
Both low and high levels of tissue turnover were associated with increased risk of all-cause mortality in postmenopausal women. Overall, these results highlight the importance of bone and soft tissue homeostasis.