Reduced kidney function is associated with BMD, bone loss and markers of mineral homeostasis in older women: a 10-year longitudinal study

Abstract

SummaryKidney function decreases with age; however, the long-term influence on bone density (BMD) in older women already at risk of osteoporosis is unknown. We followed kidney function and bone loss for 10 years. Declining kidney function was adversely associated with bone loss and mineral homeostasis in old women, though it attenuated with advanced aging.IntroductionExisting studies do not fully address the relationship between kidney function and bone metabolism with advanced aging in Caucasian women. This study describes the association between kidney function, BMD, bone loss and bone metabolism in older women and provides a review of the available literature for context.MethodsWe studied participants from the OPRA cohort with follow-up after 5 and 10 years. Using plasma cystatin C (cysC), estimated glomerular function rate (eGFR) was evaluated at age 75 (n = 981), 80 (n = 685) and 85 (n = 365). Women were stratified into “normal” function (CKD stages 1–2), “intermediate” (stage 3a) and “poor” (stages 3b–5), and outcome measures—BMD, bone loss and markers of mineral homeostasis—were compared.ResultsFemoral neck (FN) BMD positively associated with kidney function at 75 years old ( widehat{beta} = 0.001, p = 0.028) and 80 years old ( widehat{beta} = 0.001, p = 0.001), although with small effect size. Prevalence of osteoporosis (FN T-score ≤ − 2.5) did not differ with kidney function. Measured at age 75, women with poor kidney function had higher annual percentage bone loss over 5 years compared to those with normal function (2.3%, 95% CI 1.8–2.8 versus 1.3%, 95% CI 1.1–1.5, p = 0.007), although not when measured from age 80 or 85. Additionally, markers of mineral homeostasis (PTH, phosphate, vitamin D, calcium), CRP and osteocalcin differed by kidney function.ConclusionsIn old women, kidney function is associated with BMD, bone loss and altered mineral homeostasis; probably, a relationship attenuated in the very elderly.