Table 1.

Characteristics of included studies.

References, Country	Mean age, Sex	Subtypes of dementia	Type of study	Sample size	Diet/Serum/ Supplements	Dose: highest comparison lowest	OR (95%Cl)	Adjustment for covariates	NOS score
Aoki et al. (2021), Japanese	40–64, /	Dementia	Cohort study	3,739/670	Diet	Four- vs. One-fold	0.50 (0.34–0.74)	Age, sex, smoking, energy intake, region, history of stroke, docosahexaenoic acid, and docosahexaenoic acid	7
Gray et al. (2008), USA	≥65, /	Dementia	Cohort study	964/122	Supplements	/	0.98 (0.77–1.25)	age, sex, education, exercise, smoking status, self-reported health, and coronary heart disease	8
Engelhart et al. (2002), Netherlands	≥55, /	Dementia	Cohort study	5,395/146	Diet	>15.5 vs. <10.5 mg/d	0.82 (0.66–1.00)	Age, sex, baseline Mini-Mental State Examination score, alcohol intake, education, smoking habits, number of pack-years smoked, body mass index, total energy intake, presence of carotid plaques, and use of antioxidant supplements	8
Olson (2000), USA	71–93, Male	Vascular dementia/AD/Other dementia	Case-control study	3,385/2,999	Supplements	/	0.58 (0.17–2.01)/ 1.03 (0.47–2.25)/ 0.60 (0.23–1.59)	Age, years of formal education, history of stroke, and apoE phenotype	8
Basambombo et al. (2017), Canada	>65, /	AD/Other dementia	Cohort study	5,269/ 821	Supplements	/	0.62 (0.39–0.98)/0.61 (0.41–0.90)	Age, gender and education, ever regular smoking, alcohol drinking, regular physical activity, NSAID use, history of diabetes, and vascular risk factors	7
Luchsinger et al. (2003), USA	≥65, /	AD	Cohort study	4,023/242	Diet	Four- vs. one-fold	0.98 (0.67–1.44)	Age, sex, APOE 4 allele presence, smoking status, and years of education	6
Morris et al. (2002), USA	≥65, /	AD	Cohort study	815/131	Diet	10.4–43.0 vs. <7.0 IU/d	0.30 (0.10–0.92)	Age, sex, education, APOE 4 status, race, an interaction term between race and APOE 4, and period of observation	8
Zandi et al. (2004), USA	≥65, /	AD	Cohort study	5,092/355	Supplements	/	0.53 (0.20–1.12)	Age, the squared deviation of age from the population median, sex, education and APOE 4	6
Devore et al. (2010), Netherlands	>55, /	Dementia/AD	Cohort study	4,751/407	Diet	18.5 vs.9.0 mg/day	0.75 (0.58–0.97)/0.75 (0.57–1.00)	Age, education, APOE ε4 genotype, total energy intake, alcohol intake, smoking habits, and BMI	6
Corrada et al. (2005), USA	/, /	AD	Cohort study	579/57	Diet+ Supplements	Three- vs. one-fold	0.62 (0.32-1.20)	Gender, education, and baseline age and caloric intake	8
Morris et al. (2005), USA	71–93, Male	AD	Cohort study	1,041/162	Diet	The difference between high and low intake was 5 mg/d	0.74 (0.62-0.88)	Age, sex, race, education, APOE 4, the interaction between race and APOE, frequency of participation in cognitive activities, time from determination of disease-free status to clinical evaluation of incident disease, and intakes of saturated fat, trans unsaturated fat (g/d), and docosahexaenoic acid	7
Laurin et al. (2004), USA	45–68, Male	Dementia /AD/Vascular dementia	Cohort study	2,459/235	Diet	29.9 vs. 3.8 mg/d	1.33 (0.90–1.96)/1.58 (0.87–2.85)/1.07 (0.41-2.78)	Age, education, smoking status, alcohol intake, body mass index, physical activity, systolic and diastolic blood pressures, year of birth, total energy intake, cholesterol concentration, history of cardiovascular disease, supplemental vitamin intake, and apolipoprotein E e4	7
Kryscio et al. (2017), USA	≥62, /	Dementia	Cohort study	1,799/71	Supplements	400 IU/d vs. no use	0.88 (0.64–1.20)	Age, Black ethnicity, APOE ε4 carrier status, college education, baseline MIS score	8
von Arnim et al. (2012), Germany	65–90, /	Dementia	Case-control study	74/158	Diet	0.51 vs. 0.08 μM	0.71 (0.24–2.13)	School education, BMI, alcohol consumption, smoking status, and current dietary supplement use	6
Paganini-Hill et al. (2016), USA	≥90, /	Dementia	Cohort study	587/293	Supplements	/	0.86 (0.67–1.10)	Age, sex and education	6