Methods
We tried to conduct and report this meta-analysis in comply with
Preferred Reporting Items for
Systematic Reviews and Meta-Analyses (PRISMA)16.
Literature search
We searched PubMed, Cochrane
library, Web of Science, China National Knowledge Infrastructure(CNKI),
Wanfang, China Biology Medicine disc (CBM), and Weipu database for the
study on the association between blood pressure variability and
cognitive function. The search terms included ”blood pressure
variability” OR ”BPV” OR ”ambulatory blood pressure” and ”cognitive
function” ”OR ”cognitive functioning”. The search was carried out by
combining subject words and free words. Retrieval time limit was from
the date of establishment of each database to July 15, 2021.
Inclusion and exclusion criteria
The inclusion criteria for this meta-analysis were: Study type: a
publicly published case-control study on blood pressure variability and
cognitive function; Research population: patients aged 18 to 80 years
old and diagnosed with essential hypertension; Control: CI group and no
CI group; The outcome indicators included blood pressure et al;
Language: Chinese or English article. The exclusion criteria of this
meta-analysis were: patients with severe cardiovascular diseases and
other major diseases; articles that repeatedly publish or use the same
data; studies with incomplete data.
Literature screening and data extraction
Two researchers independently
searched and screened relevant documents. The search results were
imported into Endnote for double-checking, and then the initial
screening was carried out based on the abstracts of the literature to
eliminate irrelevant or unusable documents. After completion, the
researchers collected and recorded following information, including the
author, publication year, country, age, sample size, outcome indicators,
findings.
Quality Evaluation
The type of studies included in this meta-analysis was case-control
study, so it was scored according to the Newcastle-Ottawa Scale (NOS)
Literature Quality Evaluation Scale17. The full scale
of the scale was 10 points. The evaluation items mainly included three
items: population selection, comparability, and exposure. If the quality
score was less than 5, it indicated a high risk of bias and needs to be
excluded. Disagreements in the evaluation results were resolved through
further discussion.
Statistical processing
We used RevMan 5.3 for data meta-analysis. Relevant indicators were
visually displayed in forest plots, and funnel plots were used to detect
the populations. Continuous variables were represented by the
mean difference (MD) and its 95%
confidence interval (CI). If I2≤50% or
P>0.10, the heterogeneity of the study was small, and the
fixed-effects model was adopted; if
I2>50% or P ≤0.10, the random-effects
model was adopted. P<0.05 indicated the differences between
two groups were statistically different.