A new study has found that lower level of sodium in the blood, or hyponatremia,
is linked with declines in cognitive function with advancing age. The results,
which are described in an upcoming issue of the Clinical Journal of the
American Society of Nephrology (CJASN)
, raising the possibility that
addressing sodium levels may help preserve cognition as individuals age.

Hyponatremia occurs when the sodium level in the blood falls below 135
mmol/L. Mild hyponatremia was once thought to be asymptomatic, but recent
studies suggest that it may be associated with higher risks of attention
deficits, gait disturbances, falls, cardiovascular events, and even premature
death. Severe hyponatremia has been linked with cognitive
 and neurological disturbances, but the association
between different levels of serum sodium and
cognition in older adults had been uncertain.

To investigate, Kristen Nowak, PhD, MPH (University of Colorado Anschutz
Medical Campus) and her colleagues examined information on 5435 asymptomatic
community-dwelling men aged >65 years who were followed for a median of 4.6
years. A total of 100 men had serum levels indicative of hyponatremia.

The researchers found that slightly lower sodium levels in the blood
were related to both cognitive impairment and declines in cognitive function
over time. Compared with men with sodium levels of 141-142 mmol/L, men with
levels of 126-140 mmol/L were 30% more likely to have cognitive impairment at
baseline and 37% more likely to experience cognitive decline over time. The
investigators also found an association of high serum sodium (143-153 mmol/L)
with cognitive
 over time.

“Slightly lower sodium levels in the blood are likely to be
unnoticed in clinical practice,” said Dr. Nowak. “Because both
slightly lower serum sodium levels and mild changes in cognitive function are
common occurrences with advancing age, future research on this topic is
important—including determining whether correcting lower sodium levels affects
cognitive function.”

SOURCE: https://medicalxpress.com/news/2018-02-blood-sodium-affect-cognition-older.html

Nowak et al:
Serum Sodium and Cognition in Older Community-Dwelling Men;  http://cjasn.asnjournals.org/content/early/2018/02/07/CJN.07400717.abstract