TABLE 3.

Summary of the results by cognitive domain, effect metric and adjustments of the included studies.

	Global				Memory				Executive functions				Attention
Study	Effect metric	Baseline levels	Final levels	Change in levels	Effect metric	Baseline levels	Final levels	Change in levels	Effect metric	Baseline levels	Final levels	Change in levels	Effect metric	Baseline levels	Final levels	Change in levels	Adjustments
Akbaraly et al., 2010	F		NS		F		NS		F		NS						Age, gender, education or occupation, marital status, smoking, alcohol, physical activity, depression, coronary heart disease
Bangen et al., 2019	β	–	–	NS	β	–	NS	NS	β	–	–	NS					Age, gender, education, smoking
Creavin et al., 2012	β		NS						β		–		β		NS		Age, social class, smoking, alcohol, premorbid cognition
Dearborn et al., 2014, women					β	–		NS	β	–		NS	β	NS		NS	Age, education, race-center, smoking, alcohol, history of coronary heart disease
Dearborn et al., 2014, men					β	–		NS	β	–		NS	β	NS		NS
Gallagher et al., 2016					β			NS	β			NS					Age, gender, duration of follow-up, cognitive status at baseline
Harrison et al., 2015	β	NS		NS	β	NS		NS					β	NS		NS	Gender, education, smoking, alcohol, marital status, history of stroke/ischemic heart disease/heart failure
Ho et al., 2008	OR	–		–													Age, gender, education, smoking, alcohol, depression, level of leisure activities, APOE-e4, baseline MMSE, years of follow-up
Katsumata et al., 2012	β	NS		NS	β	NS		NS	β	–		NS					Age, gender, education
Kazlauskaite et al., 2020					β	NS NS		NS NS	β	NS		NS	β	NS		–	Age, education, financial strain, site–race, smoking, alcohol, physical activity, sleep difficulty, depression, anxiety, vasomotor symptoms, menopausal stages/hormone therapy
Knopman et al., 2009					β			NS	β			–	β			NS	Age, gender, education, race
Komulainen et al., 2007	OR	NS	NS		OR		–						OR		NS		Age, education, depression
Lee et al., 2010	F	–		–													Age, gender, education, height, weight, baseline MMSE, years of follow-up
Liu et al., 2013	OR	NS		+													Smoking
McEvoy et al., 2012, women	β	NS		NS	β	NS		NS	β β	NS NS		– NS					Age, education, depression, practice effect
McEvoy et al., 2012, men	β	NS		NS	β	NS		NS	β β	NS NS		NS NS
Neergaard et al., 2017	OR OR		NS NS						OR		NS						Age, education, smoking, alcohol, physical activity, hormone replacement therapy
Overman et al., 2017					β, OR β, OR			NS NS					β, OR			NS	Age, education, center, smoking, alcohol, depression, physical activity, heart disease/stroke
Przybycien-Gaweda et al., 2020	β	NS	–	NS	β	–	–	NS	β	–	–	NS	β β	– NS	– –	NS NS	Age, gender, education, smoking, alcohol, depression, leisure time activity, APOE-e4, cardiovascular disease/stroke
Raffaitin et al., 2011	HR	–		–	HR	–		–	HR	–		NS					Age, gender, education, city center, smoking, depression, APOE-e4, cardiovascular disease, score on test at baseline
Shigaeff et al., 2017					U	NS NS NS	NS NS NS		U	NS NS NS NS	NS NS NS –		U	NS NS	NS NS		Age, education
Soldevila-Domenech et al., 2021	β			NS	β			NS	β			NS					Age, gender, education, IQ, smoking, baseline weight, prediabetes, diabetes, use of treatment for high cholesterol, use of tranquilizers or sedatives, intervention group
van den Berg et al., 2007	β	NS		+	β	NS NS		NS NS	β	NS		+	β	NS		+	Gender, education, depression
Viscogliosi et al., 2016									std. β	–		–					Potentially confounding variables
Viscogliosi et al., 2017	std. β	NS		–													Age, education, marital status, depression, APOE-e4, cerebrovascular disease, baseline MMSE, incidence of ADLs disability, interaction term (MetS)*(baseline MMSE score)
Wang et al., 2021	F	–	–														Age, gender, education, professional characteristics, smoking, alcohol, living status
Watts et al., 2013	std. β	NS	NS	NS	std. β	NS	NS	NS					std. β	NS	NS	NS	Age, gender, education, APOE-e4
Wu and Chen, 2021		–			HR, KM		NS	NS					HR, KM		– NS NS	– NS NS	Age, gender, education, smoking, coronary artery disease, hypertension, diabetes type 2
Xiong et al., 2006	F			NS													Age at Time 3, education, smoking, alcohol, baseline TICS-m
Yaffe et al., 2004	RR	NS	–														Age, education, race, alcohol, depression, stroke, statin use, baseline 3MS
Yaffe et al., 2007	β	NS		–	β	NS		NS									Age, gender, education, born in the USA, smoking, alcohol, depression, history of stroke, history of myocardial infarction, missing pattern indicator
Yaffe et al., 2009	OR		NS														Age, education, race, depression, raloxifene hydrochloride treatment

A plus (+) sign indicates a higher performance of participants with metabolic syndrome and a minus (–) sign a lower performance in the respective test. F, F-test (ANOVA); U, Mann–Whitney test; β, beta coefficient; std. β, standardized beta coefficient; OR, odds ratio; HR, hazard ratio; RR, risk ratio; KM, Kaplan–Meier curves; NS, not significant; MetS, metabolic syndrome; APOE-e4, e4 allele of the apolipoprotein E; MMSE, Mini-Mental State Examination; IQ, intelligence quotient; ADLs, Activities of Daily Living; TICS-m, Modified Telephone Interview for Cognitive Status; 3MS, Modified Mini-Mental State Examination; USA, United States of America.