Highlights in clinical autonomic neurosciences: Brain volume and autonomic regulation

Cognitive Status, Gray Matter Atrophy, and Lower Orthostatic Blood Pressure in Older Adults

BACKGROUND

Associations between orthostatic blood pressure and cognitive status (CS) have been described with conflicting results.

OBJECTIVE

We hypothesize that long-term exposure to lower orthostatic blood pressure is related to having worse CS later in life and that atrophy of regions involved in central regulation of autonomic function mediate these associations.

METHODS

Three-to-four measures of orthostatic blood pressure were obtained from 1997-2003 in a longitudinal cohort of aging, and average systolic orthostatic blood pressure response (ASOBPR) was computed as % change in systolic blood pressure from sit-to-stand measured at one minute post stand. CS was determined in 2010-2012 by clinician-adjudication (n = 240; age = 87.1±2.6; 59% women; 37% black) with a subsample also undergoing concurrent structural neuroimaging (n = 129). Gray matter volume of regions related to autonomic function was measured. Multinomial regression was used to compare ASOBPR in those who were cognitively intact versus those with a diagnosis of mild cognitive impairment or dementia, controlling for demographics, trajectories of seated blood pressure, incident cardiovascular risk/events and medications measured from 1997 to 2012. Models were repeated in the subsample with neuroimaging, before and after adjustment for regional gray matter volume.

RESULTS

There was an inverse association between ASOBPR and probability of dementia diagnosis (9% lower probability for each % point higher ASOBPR: OR 0.91, CI95%  = 0.85-0.98; p = 0.01). Associations were similar in the subgroup with neuroimaging before and after adjustment for regional gray matter volume.

CONCLUSION

ASOBPR may be an early marker of risk of dementia in older adults living in the community.

Sub-clinical orthostatic hypotension is associated with greater subjective memory impairment in older adults

INTRODUCTION

Orthostatic blood pressure (BP) is a measure of cardiovascular autonomic function. Orthostatic BP dysregulation may lie on the causal pathway to dementia. Subjective memory impairment (SMI) is commonly reported by older people some of whom may progress to dementia. We hypothesised that sub-clinical orthostatic hypotension would be associated with SMI and explored these associations according to sex.

METHODS

Cross-sectional analysis of data from 4340 participants aged 50 and over collected during the first wave (2009-2011) of the cohort study, The Irish Longitudinal Study on Ageing. Subjective memory was rated according to a 5-point scale ranging from 'poor' to 'excellent'. BP was measured during orthostatic stress using continuous non-invasive beat-to-beat recording over 2 min.

RESULTS

2% reported 'poor' subjective memory, 12.3% 'fair' , 38% 'good', 33% 'very good' and 14.6% 'excellent'. After controlling for several potential confounding factors including cardiovascular risk, objective cognition, and depressive symptoms mean systolic orthostatic BP was lowest in those with poor subjective memory: 92.2 mmHg (CI95% = 87.1, 97.3) versus excellent 99.3 mmHg (CI95% = 97.4, 101.2); p = 0.011. Further adjustment for supine systolic BP suggested that men with poor subjective memory reached the lowest average systolic orthostatic BP and had the greatest impairment in systolic orthostatic BP stabilisation to baseline levels at 10 s post-stand (-6.64 mmHg; CI95% = -11.49, -1.79; p = 0.007).

CONCLUSIONS

Sub-clinical orthostatic hypotension is associated with SMI, and there are sex-specific relationships evident in this population-based cohort. Subtle cardiovascular autonomic dysfunction may represent a modifiable risk marker at an early stage of cognitive decline in older adults. Copyright © 2016 John Wiley & Sons, Ltd.