Hyponatremia is amongst the most familiar electrolyte disturbances seen in the population, especially in geriatric inpatients. Our study demonstrates the value of checking and improving serum sodium values, that too amongst the elderly age group. We found results of improvement in sodium values on the various CGA parameters. 14% of patients had severe hyponatremia (serum sodium <125 meq/L) amongst the geriatric hyponatremic population in our study, moderate (125≤Na<130) hyponatremia was seen in 21%, and mild hyponatremia (130≤Na<135) was seen in 65%.
Persons with severe hyponatremia demonstrated greater average age (71.60 ± 6.6 years) in comparison with moderate (66.60 ± 5.1 years), and mild hyponatremia group (67.70 ± 5.5 years, P=0.04). Similar findings were seen in other studies, meaning the prevalence of patients with severe hyponatremia becomes significantly greater as age advances.[13] Change in serum sodium levels from admission to discharge was significantly greater in the severe group (12.3 ± 6.6 meq/L), as compared to the mild (3.2 ± 1.6 meq/L) and moderate groups (7.1 ± 2.9 meq/L). Notably, the improvement in ADL, TUG, and HMSE scores with serum sodium improvement was more in the hyponatremic group (8.8 ± 10.1, 2.2 ± 2.5, and 1.7 ± 2.3 respectively) when compared to the normonatremic reference group (4.7 ± 9.0, 1 ± 2.0, and 0.7 ± 1.3 respectively, P<0.05). Although HG improvement was also more remarkable in the hyponatremic group, it was not statistically significant. Assuming that the treatment measures and any geriatric rehabilitation efforts were made identically in both the hyponatremic and normonatremic groups, these differences in CGA values are most likely accounted for, at least in part, by the improvement of the serum sodium levels themselves.
Similar trends of more remarkable change in the ADL, TUG, HG, and HMSE values were seen in the various subgroups according to the severity of hyponatremia. All the severely hyponatremic patients demonstrated a greater change in the CGA parameters from admission to discharge after improving their serum sodium levels. This finding is very important, signifying that with the correction of sodium levels in the severely hyponatremic group, we can improve the motor and cognitive performance of geriatric patients quite significantly. The better performance in the discharge CGA parameters of the severe hyponatremia group may be explained by the subjective more enormous improvement from a comparatively poor initial performance.
Other studies like the INSIGHT study have revealed the result of sodium control (with Tolvaptan) on the results of various other tests evaluating neurocognitive domains in the elderly.[14] Renneboog et al. analyzed response times to various visual and auditory stimuli and revealed lower latency (by 8.6%) after correcting serum sodium levels.[15] Other studies have demonstrated that lower sodium levels associate with significant cognitive impairment, further cognitive decline, and the development of dementia.[16,17] In our study, we also demonstrated significant motor performance improvement in the patients after improving serum sodium levels. Brinkkoetter et al. could not detect any reliable improvement in the motor power in the elderly.[18] This again demonstrated the clinical importance of our study. Falls in the elderly are a significant problem and one of the geriatric giants. The serum sodium level analysis must be done carefully in the geriatric age group presenting with falls, and sodium improvement may help the prevention of the same. This may reduce fractures, resulting in lower morbidity, mortality, and overall economic burden.
As per our knowledge, this is the first study of its kind studying the correlation of HMSE with hyponatremia. The baseline ADL, HG, and HMSE were lower in the severely hyponatremic group than the mild and moderate one, although it was statistically significant only for the HMSE value (24.1 ± 2.5 v/s 22.6 ± 2.8 v/s 21.1 ± 4.0; P=0.0007). TUG test value was significantly higher in the severe (17.90 ± 3.40 s) when compared with the mild (14.60 ± 3.50 s) and moderate groups (16.40 ± 4.20 s, greater value meaning worse performance). Effect seen with ADL, TUG, and HMSE were not be reproduced with the other tests (HG here), implying that the exact impact of hyponatremia is yet incompletely understood. In spite of the proposed age-associated decrease in the renal capability for producing dilute urine, the expected lower reference level of serum sodium in the elderly was just lesser than the universal levels of 135 mEq/L.[18] This is an important finding, implying that even milder forms of hyponatremia should not be considered a normal variation with age. Our study has limitations. Baseline CGA parameter results can be affected by other underlying diseases. However, we minimized this by including age, comorbidity, and primary diagnosis matched group who is normonatremic.