Surprising Link Between Sodium Intake and Postmenopausal Hip Fracture Risk

SAN FRANCISCO, CA—Higher levels of sodium intake are associated with a lower risk of hip fractures among postmenopausal women, but adherence to sodium-intake recommendations for cardiovascular health does not affect bone mineral density (BMD), according to findings from the Women’s Health Initiative (WHI) reported at the 2015 ACR/ARHP Annual Meeting.

“The surprising association of higher sodium intakes with fewer hip fractures merits further study,” reported Monique Bethel, MD, Georgia Regents University, Augusta, Georgia, and coauthors.

The authors noted that “the role of sodium intake in the pathogenesis of osteoporosis is controversial.” Currently, federal nutrition guidelines recommend a sodium intake of <2,300mg per day and, in certain populations, <1,500 mg per day. The investigators postulated that “dietary interventions for osteoporosis may be a safe and effective means to prevent osteoporosis on a population level.”

The study examined the association of sodium intake with changes in BMD and incident fractures over 11.4 years of average follow-up among 69,735 postmenopausal women 50 to 79 years of age enrolled in the WHI between October 1993 and December 1998 at 40 US clinical centers. The Food Frequency Questionnaire was used to assess intakes of calcium, magnesium, and vitamin D. Analyses between changes in BMD, calibrated intake of sodium, potassium, and calcium, and incident bone fractures were adjusted for demographic, clinical, and medication factors.

‘Incident clinical fractures were determined by self-report,” the investigators noted, while “BMD of the total hip, femoral neck, anterior-posterior lumbar spine and total body was measured at baseline, year 3, and year 6.”

Results showed that 910 hip fractures occurred below the median sodium intake (<2,892 mg per day), compared with 533 hip fractures above the median sodium intake, ≥2,892 mg per day (P=0.03). “However, in sensitivity analyses that included BMI in the fracture models, there was no association of sodium with all fractures or any fracture site,” they noted.

A model that examined the association of sodium intake with changes in BMD by median sodium intakes in a subsample of 4,426 women found that levels of sodium intake above or below 2300 mg per day were not significantly associated with changes in BMD at any skeletal site from baseline to three or six years or with incident fractures.

“The association between sodium intake and BMD changes did not depend on calcium intake,” Dr. Bethel concluded.