Electrolyte disorder boosts fracture risk in elderly, but connection to osteoporosis is unclear

Dutch researchers recently confirmed what several prior reports have suggested about the blood disease hyponatremia - namely, that low levels of sodium in the blood can increase the risk of fractures in elderly people with or without osteoporosis.

The study, which appeared in the Journal of Bone and Mineral Research (JBMR), specified that individuals over the age of 70 with the blood condition have a 39 percent greater likelihood of suffering a broken bone, even after statistical adjustment for body mass index, gender, age, disabilities, diuretic use, diabetes and falls.

Researchers said that all in all, hyponatremia increased participants' mortality risk by 21 percent.

Hyponatremia is the most common electrolyte disorder in the U.S., according to the National Institutes of Health (NIH). It occurs when too little sodium exists in the fluid surrounding one's cells.

In aging Americans, hyponatremia can be caused by dietary insufficiencies, congestive heart failure, diuretics or certain medications, the NIH states.

For the new study, researchers analyzed blood samples taken from more than 5,200 citizens of the Netherlands, all of whom were at least 70 years old. The team found that 7.7 percent of the entire group had mild hyponatremia, which scientists defined as having roughly 133.4 millimoles of sodium per liter of blood (mmol/L).

By comparison, the American Academy of Family Physicians defines a sodium blood level lower than 125 mmol/L as an "acute" case of the disease.

In the study, not only did the electrolyte imbalance heighten the risk of all fractures, but it also specifically raised the likelihood of vertebral pressure fractures by 78 percent.

The connection between the blood disorder and progressive bone loss is unclear, since patients with hyponatremia did not have significantly lower bone densities. In this regard, a previous report published in the Clinical Journal of the American Society of Nephrology found that hyponatremia increases fracture risk among elderly women, even when they are osteoporosis-free.

However, a March 2010 study in the JBMR posited a causal relationship between some cases of hyponatremia and osteoporosis.