The relationship between dehydration and etiologic subtypes of major neurocognitive disorder in older patients.

Purpose: Studies investigating associations between etiologic subtypes of major neurocognitive disorder (MND) and dehydration frequency are lacking. The aim of this study was to investigate the prevalence and risk factors of dehydration among older adults with and without MND (dementia), and across different etiologic subtypes of MND.

Methods: This cross-sectional study included adults aged ≥ 65 years old from one geriatric outpatient clinic. Dehydration was defined as a calculated [1,86 × (Na + K) + 1,15 × glucose + urea + 14] plasma osmolarity of > 295 mOsm/L.Clinical characteristics and measures of comprehensive geriatric assessments of patients with dehydration and normohydration were compared. MND was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition criteria. The underlying etiologic subtypes were determined by specific diagnostic criteria.

Results: Of the 1377 patients 72% were female, the mean age was 80 ± 8 years, and 575 had dementia. Dehydration was more common in patients with dementia than those without dementia (58% vs. 53%, p = 0.044). The prevelance of dehydration was 57%, 62%, 54%, 57% and 68% in Alzheimer's disease, Parkinson's disease dementia, fronto-temporal dementia, dementia with Lewy bodies, and vascular dementia, respectively (p ≥ 0.05). MND was associated with dehydration (OR 1.26, 95% CI 1.01-1.57; p = 0.037) after adjustment for age and sex. In multivariable analysis, among patients with dementia, hypertension, DM, CKD, and dysphagia were more common while mean Mini-Mental State Examination score was lower in those who had dehydration versus no dehydration in older patients with dementia (p < 0.05).

Conclusion: Dehydration is slightly associated with the presence of MND independent of age and sex. However, dehydration is also quite common in older patients without cognitive disorders. Therefore, hydration status should be monitored in older adults irrespective of neurocognitive status. Hypertension, DM, CKD, dysphagia and severity of cognitive dysfunction were associated with dehydration in patients with dementia. The prevalence of dehydration is highest in patients with vascular dementia.