Effects of heart rate variability and blood pressure on cognition in healthy and clinical cohorts
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Australia’s aging population has heightened demand for earlier detection and prevention methods for dementia. Studies have shown that autonomic dysfunction precedes mild cognitive impairment, a precursor to dementia (Collins et al., 2012). The present study explores the links between heart rate variability (HRV) (reflecting autonomic activity), blood pressure (BP), and cognitive function in non-clinical and clinical cohorts (depression, diabetes (type 1 and 2), and hypertension). Participants were added to an existing database (De Leon, 2009, Smith, 2010) (n=100) to produce a cumulative sample of n=297. The experimental protocol commenced with three baseline BP measurements, the Lifestyle Appraisal Questionnaire (Craig et al., 1996) and the Disease State Questionnaire (Giblin, 2013). The participant underwent two electrocardiogram recordings for HRV analysis (10 minutes of baseline and 10 minutes of a cognitive task). Two psychometric tests were then administered: the Mini-Mental State Examination (Folstein et al., 1975) and the Cognistat (Kiernan et al., 1987). Finally, three additional BP measurements completed the study protocol. Higher baseline parasympathetic activity was significantly correlated (p=<0.05) to better cognitive performance (e.g. memory) in females 18-50 years and males 51-65 years however this was also correlated to poorer cognitive scores (e.g. judgment) in females 36-65 years and males 36-50 years. HRV reactivity (cognitive task minus baseline) was mostly positively correlated to cognition (e.g. comprehension) in females 18-35 and 51-65 years. Higher vagal activity was linked to higher cognitive scores (e.g. attention) in all clinical groups yet also linked to poorer cognitive scores (e.g. orientation) in the type 1 diabetes and hypertension groups. HRV reactivity was mostly positively correlated to cognition (e.g. naming) in the hypertension sample yet inversely linked to cognition in the other clinical groups. Both clinical and non-clinical groups had positive correlations between BP reactivity and cognitive performance (e.g. attention), suggesting low BP reactivity may be a predictor for cognitive decline. These initial findings contribute new knowledge to the field of HRV and cognition, particularly in clinical groups and the less-studied HRV and BP reactivity in clinical and non-clinical groups. By gaining a better understanding of early autonomic risk factors for cognitive impairment, preventative countermeasures (e.g. anti-hypertensive use and autonomic biofeedback) may be considered to slow or cease dementia progression. Delaying or stopping the development of dementia has the potential to reduce expected rises in government expenditure, lower the burden on carers and nursing homes, lengthen lifespans, and ultimately improve the quality of life in elderly populations.
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