Blood pressure variability and structural brain changes: a systematic review.

BACKGROUND: Blood pressure variability (BPV) has been linked with cognitive impairment and dementia. However, the pathophysiological mechanisms by which BPV affects cognition are unclear. This systematic review aims to assess the links between different BPV measures and white and grey matter structures. METHODS AND RESULTS: The following databases were searched from inception through to January 2021; EMBASE, MEDLINE, EMCARE and SCOPUS. Studies that reported on the relationship between within-individual BPV (short, medium or long-term variability) or a circadian blood pressure (BP) measurement and MRI assessed brain structures were included. Overall, 20 studies met the criteria and were included, of which 11 studies looked at short-term BPV, eight articles investigated visit-to-visit BPV and one study looked at a compositional BPV measurement. Due to heterogeneity in study samples, meta-analysis was not possible. Across the included studies, associations between MRI indices and BP dipping patterns were mixed; higher long-term BPV and higher sleep systolic BPV was found to be associated with lower whole brain volume and hippocampal volume. CONCLUSION: Increased BPV, in particular systolic long-term and systolic night-time BPV, appears to be associated with lower brain volume and hippocampal volume. This highlights the adverse effect that increased BPV has upon the brain, potentially contributing to cognitive decline, including dementia, in late-life.

Cerebrovascular function during cognition in Parkinson's disease: A functional transcranial Doppler sonography study.

OBJECTIVE: Recent evidence has linked cerebrovascular abnormalities with Parkinson's Disease (PD), which may provide a new neurophysiological understanding of cognitive impairment in PD. The current study aimed to compare cerebrovascular functioning, during a cognitive task and at rest, in those with and without PD. METHODS: Idiopathic PD patients (n = 30) and age- and gender-matched healthy controls (n = 30) undertook cognitive testing and completed a word generation task while blood flow velocity was monitored bilaterally with functional transcranial Doppler sonography (fTCD) of the middle cerebral arteries. The lateralisation index and its standard deviation and timing, along with the maximum peak velocity for the left and right hemispheres and their latencies and standard deviations, were calculated for each participant. RESULTS: The PD patients showed significantly more variability of the lateralisation index compared to the control group; but there were no differences in the lateralisation index itself nor in the peak velocities. In the PD group, the variability in the peak velocities showed significant positive correlations with performance on executive function tests. CONCLUSION: Normal ageing has been associated with a reduction in the lateralisation index, but no alterations in the standard deviation, suggesting that cerebrovascular functional changes associated with PD differ from those of typical ageing. The within-subject variability observed in the PD group indicate abnormalities within the neurovascular coupling response. Further, the association between the within-subject variability and executive functioning in the PD group, suggests that cerebrovascular dysfunction plays an important role in cognitive impairment in PD.

Conversion to MCI and dementia in Parkinson's disease: a systematic review and meta-analysis.

OBJECTIVE: To systematically review and meta-analyse conversion rates from normal cognition to Mild Cognitive Impairment (MCI) and dementia in Parkinson's disease (PD) patients. Reversion rates in patients with MCI (i.e. PD-MCI) were also investigated. METHODS: Electronic searches of PsycINFO, Medline and EBSCOhost were conducted in January 2018, with 1833 articles identified after duplicate removal. Articles were included if they assessed conversion/reversion in PD patients between normal cognition, PD-MCI and PD dementia (PD-D). RESULTS: In total, 39 articles met the inclusion criteria, representing 4011 patients (mean age range 58-75; 61% male). Within three years, in those with PD and normal cognition, 25% (95%CI 20-30%) converted to PD-MCI and 2% (95%CI 1-7%) converted to dementia. Of those with PD-MCI, 20% (95%CI 13-30%) converted to dementia while 28% (95%CI 20-37%) reverted back to a state of normal cognitive function. The conversion rates to MCI and dementia were higher, and reversion rates lower, when follow-up was ≥3 years. When International Parkinson and Movement Disorder Society (MDS) criteria were used to diagnose MCI, Level I criteria were associated with a greater reversion estimate from PD-MCI to normal cognitive function. CONCLUSIONS: These findings summarise the trajectory of cognitive impairment in PD and highlight that MCI is common in this patient group. Understanding cognitive trajectories in PD patients is important for patient care in terms of prognosis, as well as for identifying windows for intervention for cognitive symptoms. As the number of PD patients increases with an ageing population, this information can inform future policy and planning.