Chronic hyponatremia and association with osteoporosis among a large racially/ethnically diverse population

A retrospective study: exploring preoperative hyponatremia in elderly patients with hip fractures

BACKGROUND

This research aims to examine the frequency, age-related distribution, and intensity of preoperative hyponatremia among elderly individuals with hip fractures. This study aims to provide valuable insights into the diagnosis of preoperative hyponatremia in this patient population.

METHODS

This research involved the analysis of clinical data obtained from 419 elderly individuals with hip fractures (referred to as the fracture group) and 166 elderly individuals undergoing routine health examinations (designated as the control group). A comprehensive comparison was conducted, examining baseline characteristics such as age, gender, and comorbidities between these two groups. We further investigated variations in the incidence rate of hyponatremia, age distribution, and the severity of hyponatremia. Additionally, a subgroup analysis compared patients with femoral neck fractures to those with intertrochanteric femur fractures, specifically examining the incidence rate and severity of hyponatremia in these distinct fracture types.

RESULTS

The incidence of cerebrovascular disease was found to be higher in the fracture group as compared to the control group in our research. Nevertheless, no significant differences in general health and other comorbidities were observed between the two groups. Notably, the fracture group exhibited a greater preoperative prevalence of hyponatremia, with its severity increasing with age. Furthermore, among elderly patients with intertrochanteric femur fractures, the incidence of preoperative hyponatremia was not only higher but also more severe when compared to those with femoral neck fractures.

CONCLUSION

Elderly individuals experiencing hip fractures exhibit a notable prevalence of preoperative hyponatremia, predominantly mild to moderate, with an escalating occurrence linked to advancing age. This phenomenon is especially conspicuous among patients with intertrochanteric fractures, warranting dedicated clinical scrutiny. The administration of sodium supplementation is advisable for the geriatric demographic as deemed necessary. Addressing hyponatremia becomes crucial, as it may play a role in the etiology of hip fractures in the elderly, and rectifying this electrolyte imbalance could potentially serve as a preventive measure against such fractures.

Association of hyponatremia with bone mineral density and fractures: a narrative review

Recent studies suggest a possible association of hyponatremia with osteoporosis, falls and bone fractures. The objectives of this narrative review were to further explore this association and the related pathophysiological mechanisms and to suggest a practical approach to patients with osteoporosis or chronic hyponatremia in clinical practice. We conducted an extensive PubMed search until October 2022 with the combination of the following keywords: 'hyponatremia' or 'sodium' or 'SIADH' and 'fractures' or 'bone' or 'osteoporosis', as MeSH Terms. Review of numerous observational studies confirms a significant independent association of, even mild, hyponatremia with two- to three-fold increase in the occurrence of bone fractures. Hyponatremia is a risk factor for osteoporosis with a predilection to affect the hip, while the magnitude of association depends on the severity and chronicity of hyponatremia. Chronic hyponatremia also increases the risk for falls by inducing gait instability and neurocognitive deficits. Besides the detrimental impact of hyponatremia on bone mineral density and risk of falls, it also induces changes in bone quality. Emerging evidence suggests that acute hyponatremia shifts bone turnover dynamics towards less bone formation, while hyponatremia correction increases bone formation. The key unanswered question whether treatment of hyponatremia could improve osteoporosis and lower fracture risk highlights the need for prospective studies, evaluating the impact of sodium normalization on bone metabolism and occurrence of fractures. Recommendations for clinical approach should include measurement of serum sodium in all individuals with fracture or osteoporosis. Also, hyponatremia, as an independent risk factor for fracture, should be taken into consideration when estimating the likelihood for future fragility fracture and in clinical decision-making about pharmacological therapy of osteoporosis. Until it is proven that normalization of sodium can lower fracture occurrence, correcting hyponatremia cannot be universally recommended on this basis, but should be decided on a case-by-case basis.

Is there a causal relationship between hypothyroidism and hyponatremia?

Hyponatremia is one of the most common lab abnormalities seen in clinical practice. It has become widely accepted that hypothyroidism is a cause of euvolemic hyponatremia. The primary mechanism is thought to be due to impaired free water excretion and changes in sodium handling in the kidney. However, the clinical studies are conflicting and do not definitively confirm the association between hypothyroidism and hyponatremia. Therefore, if severe hyponatremia occurs in a patient without myxedema coma, other potential etiologies should be sought.

Hyponatremia and aging-related diseases: key player or innocent bystander? A systematic review

BACKGROUND

Hyponatremia is frequent in older age; whether it is a key player, a surrogate marker, or an innocent bystander in age-related diseases is still unclear.

OBJECTIVE

To understand the role of hyponatremia in falls, osteoporosis, fractures, and cognitive impairment in old patients.

METHOD

Eligibility criteria for study inclusions were: written in English, peer-reviewed observational and intervention studies, clinical trial, prospective and retrospective controlled cohort studies, and case-controlled studies without limitations regarding the date of publication.

INFORMATION SOURCES

Protocol available on the International Prospective Register of Systematic Reviews (PROSPERO, CRD42021218389). MEDLINE, Embase, and PsycINFO were searched. Final search done on August 8, 2021. Risk-of-bias assessment: Risk-of-Bias Assessment tool for Non-randomized Studies (RoBANS) and the Bradford Hill's criteria for causality.

RESULTS

Includes studies: One-hundred thirty-five articles retained for the revision. Synthesis of results - Falls: Eleven studies were included. Strong association between hyponatremia and falls in all the studies was found. Osteoporosis and fractures: nineteen articles were included. The association between hyponatremia and osteoporosis is unclear. Cognitive impairment: Five articles were included. No association between hyponatremia and cognitive impairment was found.

DISCUSSION

Interpretation: Falls, osteoporosis, and fractures are multifactorial. Hyponatremia is not temporally related with the outcomes; we suggest that hyponatremia may be regarded as a marker of unhealthy aging and a confounder instead of a causal factor or an innocent bystander for falls and fractures. Concerning cognitive impairment, there are no evidence supporting a real role of hyponatremia to be regarded as an innocent bystander in neurodegeneration.

Sub-acute hyponatraemia more than chronic hyponatraemia is associated with serious falls and hip fractures

BACKGROUND

Falls and hip fractures among older people are associated with high morbidity and mortality. Hyponatraemia may be a risk for falls/hip fractures, but the effect of hyponatraemia duration is not well understood.

AIMS

To evaluate individuals with periods of sub-acute and chronic hyponatraemia on subsequent risk for serious falls and/or hip fractures.

METHODS

Retrospective cohort study in the period 1 January 1998 to 14 June 2016 within an integrated health system of individuals aged ≥55 years with ≥2 outpatient serum sodium measurements. Hyponatraemia was defined as sodium <135 mEq/L with sub-acute (<30 days) and chronic (≥30 days) analysed as a time-dependent exposure. Multivariable Cox proportional-hazards modelling was used to estimate hazard ratios (HR) for serious falls/hip fractures based on sodium category.

RESULTS

Among 1 062 647 individuals totalling 9 762 305 sodium measurements, 96 096 serious falls/hip fracture events occurred. Incidence (per-1000-person-years) of serious falls/hip fractures were 11.5, 27.9 and 19.8 for normonatraemia, sub-acute and chronic hyponatraemia. Any hyponatraemia duration compared to normonatraemia had a serious falls/hip fractures HR (95%CI) of 1.18 (1.15, 1.22), with sub-acute and chronic hyponatraemia having HR of 1.38 (1.33, 1.42) and 0.91 (0.87, 0.95), respectively. Examined separately, the serious falls HR was 1.37 (1.32, 1.42) and 0.92 (0.88, 0.96) in sub-acute and chronic hyponatraemia, respectively. Hip fracture HR were 1.52 (1.42, 1.62) and 1.00 (0.92, 1.08) for sub-acute and chronic hyponatraemia, respectively, compared to normonatraemia.

CONCLUSIONS

Our findings suggest that early/sub-acute hyponatraemia appears more vulnerable and associated with serious falls/hip fractures. Whether hyponatraemia is a marker of frailty or a modifiable risk factor for falls remains to be determined.

Association between hypothyroidism and chronic kidney disease observed among an adult population 55 years and older

Hypothyroidism and chronic kidney disease (CKD) are highly prevalent conditions with a potential mechanistic link. We sought to determine whether hypothyroidism is associated with CKD among a large diverse community-based cohort.A cross-sectional study was performed (January 1, 1990-December 31, 2017) within a large integrated health system. Individuals age ≥55 years of age with outpatient measurements of thyroid stimulating hormone (TSH) and ≥2 serum creatinine values were included. Hypothyroidism was defined as TSH >4 mIU/L and/or receipt of thyroid hormone replacement and further categorized as hypothyroid status: TSH >4 mcIU/mL and attenuated-hypothyroid status: TSH <4 mcIU/mL with receipt of thyroid hormone replacement. Euthyroidism was defined as TSH <4 mIU/L and no thyroid hormone replacement. Our primary measure was CKD defined as an estimated glomerular filtration rate (eGFR) <45 mL/min/1.73 m. Multivariable logistic regression adjusting for age, sex, race, and comorbidities was used to estimate odds ratios (OR) for CKD by thyroid status.Among 378,101 individuals, 114,872 (30.4%) had hypothyroidism among whom 31,242 and 83,630 had hypothyroid and attenuated-hypothyroid statuses, respectively. Individuals with hypothyroidism had a CKD OR (95%CI) of 1.25 (1.21-1.29) compared with those with euthyroidism. Granular examination of thyroid statuses showed that hypothyroid and attenuated-hypothyroid statuses had CKD ORs (95% CI) of 1.59 (1.52-1.66) and 1.12 (1.08-1.16), respectively. A similar relationship was observed in analyses that defined CKD as an eGFR <60 L/min/1.73 m.Among individuals 55 years and older, we observed that those with hypothyroidism were more likely to have CKD. A stronger association was found among patients of hypothyroid status compared with attenuated-hypothyroid status suggesting a dose dependent relationship.