From the Journals

Reduced kidney function linked to fractures in older women



Moderate reductions in kidney function in older women are associated with an increased short-term risk of fractures, according to a study published in Osteoporosis International.

However, the longitudinal, population-based cohort study did not find an association with fracture risk either in women older than 80 years or in those with worse kidney function.

“Since the kidneys regulate homeostasis of PTH [parathyroid hormone], phosphate, calcium, and vitamin D, any disruption in function can be expected to disturb bone remodeling and have implications for skeletal health,” wrote Linnea Malmgren, MD, and colleagues from Skåne University Hospital in Malmö, Sweden.

Previous studies have found that a large proportion of older women have reduced kidney function equivalent to a diagnosis of chronic kidney disease and that it is associated with bone loss. However, there have been few studies exploring that association in a population without a diagnosis of chronic kidney disease.

In their study, Dr. Malmgren and colleagues followed 981 women aged 75 years and 685 women aged 80 years, who underwent assessment of kidney function and bone mineral density and were followed up for fracture.

They found that women who experienced an osteoporotic fracture between the ages of 75 and 80 years had significantly lower baseline kidney function, compared with those who did not experience a fracture.

Compared with women with normal kidney function at age 75, women with intermediate kidney function (estimated glomerular filtration rate 45-59 mL/min per 1.73m2) had a significant 2.21-fold higher risk of osteoporotic fracture within 2 years, a 1.51-fold higher risk up to 5 years, and an elevated risk of hip fracture.

A similar trend was seen in women with poor kidney function (eGFR less than 45 mL/min per 1.73m2), but it was not statistically significant.

The analysis also found that kidney function at age 80 years was not significantly associated with long-term fracture risk, nor was there a significant association for 10-year fracture risk in those aged 75 years.

Reduced kidney function was also associated with a higher fracture risk even in women without osteoporosis.

“As expected, fracture risk was high among those with osteoporosis, but risk seemed to further increase in women with both osteoporosis and reduced kidney function, compared with those with osteoporosis and normal function,” the authors reported.

“These findings indicate that implications for bone health and fracture risk might occur in the very common modest reduction of kidney function in the elderly, and also possibly before a diagnosis of CKD-MBD [chronic kidney disease–mineral and bone disorder].”

The study was supported by Lund University; the Swedish Research Council; Forte, Greta and Johan Kock Foundation; A. Påhlsson Foundation; A. Osterlund Foundation; H Järnhardt Foundation; King Gustav V 80-year Fund; Thelma Zoegas Foundation; Swedish Rheumatism Foundation; Skåne University Hospital Research Fund; and the Research and Development Council of Region Skåne, Sweden. No conflicts of interest were declared.

SOURCE: Malmgren L et al. Osteoporos Int. 2019 Nov 21. doi: 10.1007/s00198-019-05152-x.

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