Kidney Function During Ageing and its Association with Bone Mass, Fracture and Mortality

Sammanfattning: Osteoporosis and osteoporosis related fractures are a major health care challenge both in Sweden and globally. The cost and suffering from osteoporosis are expected to increase since the population of elderly is increasing. Bone health can be affected by altered mineral homeostasis, which in its turn can be affected by reduced kidney function. However, the course of age-related decline in kidney function and its association to osteoporosis andfracture in the very elderly need further investigation since longitudinal data are scarce. Therefore, this thesis has two main aims; 1) to investigate kidney function during ageing and 2) its association to bone health in a cohort ofelderly women.Data was collected through the Malmö Osteoporosis Prospective Risk Assessment (OPRA) cohort, a prospective cohort of 1044 community dwelling women, all aged 75 and followed for ten years with reinvestigations at age 80and 85. Data on BMD, fracture and blood biochemistry was available at all three time points.Estimated kidney function greatly depends on which marker and study equation is used. The discrepancies are to such an extent that could affect whether a person is diagnosed with chronic kidney disease (CKD) or not, of particular importance in the elderly. Only women with the worst kidney function, corresponding to CKD stage 3b-5, had continuously increased mortality risk. This indicates that an age-dependent CKD definition would be of valuein elderly women.Kidney function in elderly women was associated with markers of mineral homeostasis, bone loss and BMD, but the effect size was relatively small compared to other risk factors. Also, fracture risk was increased only in womenwith mild-moderate reduction of kidney function (CKD stage 3a) and not in women with the worst kidney function (CKD stage 3b-5). Low BMD was associated with increased fracture risk independent of kidney function. Havingboth reduced kidney function and osteoporosis could present an additional risk increase.In conclusion, estimated kidney function in elderly women greatly depends on method of estimation and the results advocate for an age-adapted CKD definition. Maintaining adequate kidney function is important formaintaining bone health, although in old age it is probable that the effect size of any single specific risk factor is smaller compared with younger individuals.