The role of diet on the risk of dementia in the oldest old: The Monzino 80-plus population-based study

Association between Mediterranean diet and dementia and Alzheimer disease: a systematic review with meta-analysis

BACKGROUND

Dementia affects 5-8% of the population aged over 65 years (~50 million worldwide). Several factors are associated with increased risk, including diet. The Mediterranean diet (MedDiet) has shown potential protective effects against several chronic diseases.

AIMS

This systematic review with meta-analysis aim was to assess the association between adherence to the MedDiet and the risk of dementia in the elderly.

METHODS

PRISMA-2020 guidelines were followed. PubMed/MEDLINE and Scopus were searched on 17 July 2023. The Newcastle-Ottawa Scale tool was used to assess the risk of bias. The protocol was pre-registered in PROSPERO (registration number: CRD 42023444368). Heterogeneity was assessed using the I2 test. Publication bias was assessed by visual inspection of the funnel plot and by Egger's regression asymmetry test. The final effect size was reported as OR or HR, depending on the study design of the included studies.

RESULTS

Out of 682 records, 21 were included in the analysis. The pooled OR was 0.89 (95% CI = 0.84-0.94) based on 65,955 participants (I2 = 69.94). When only cohort studies were included, HR was 0.84 (95% CI = 0.76-0.94) based on 55,205 participants (I2 = 89.70). When only Alzheimer Disease was considered OR was 0.73 (95% CI = 0.62-0.85) based on 38,292 participants (I2 = 63.85).

DISCUSSION

Despite the relatively low risk reduction associated with higher adherence to MedDiet among elderly, it should be considered that this population is the most affected.

CONCLUSIONS

Adherence to MedDiet could be an effective non-pharmacological measure to reduce the burden of dementia, even among elderly.

Dairy Intake and Risk of Cognitive Decline and Dementia: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies

Dairy intake may influence cognition through several molecular pathways. However, epidemiologic studies yield inconsistent results, and no dose-response meta-analysis has been conducted yet. Therefore, we performed a systematic review with a dose-response meta-analysis about the association between dairy intake and cognitive decline or incidence of dementia. We investigated prospective studies with a follow-up ≥6 mo on cognitive decline or dementia incidence in adults without known chronic conditions through a systematic search of Embase, Medline, Cochrane Library, Web of Science, and Google Scholar from inception to 11 July 2023. We evaluated the dose-response association using a random-effects model. We identified 15 eligible cohort studies with >300,000 participants and a median follow-up of 11.4 y. We observed a negative nonlinear association between cognitive decline/dementia incidence and dairy intake as assessed through the quantity of consumption, with the nadir at ∼150 g/d (risk ratio: 0.88; 95% confidence interval: 0.78, 0.99). Conversely, we found an almost linear negative association when we considered the frequency of consumption (risk ratio for linear trend: 0.84; 95% confidence interval: 0.77, 0.92 for 1 time/d increase of dairy products). Stratified analysis by dairy products showed different shapes of the association with linear inverse relationship for milk intake, whereas possibly nonlinear for cheese. The inverse association was limited to Asian populations characterized by generally lower intake of dairy products, compared with the null association reported by European studies. In conclusion, our study suggests a nonlinear inverse association between dairy intake and cognitive decline or dementia, also depending on dairy types and population characteristics, although the heterogeneity was still high in overall and several subgroup analyses. Additional studies should be performed on this topic, including a wider range of intake and types of dairy products, to confirm a potential preventing role of dairy intake on cognitive decline and identify ideal intake doses. This review was registered at PROSPERO as CRD42020192395.

Mediterranean diet is associated with lower white matter lesion volume in Mediterranean cities and lower cerebrospinal fluid Aβ42 in non-Mediterranean cities in the EPAD LCS cohort

The Mediterranean diet (MedDiet) has been associated with better brain health and reduced incidence of dementia. Few studies have compared the effects of the MedDiet in early Alzheimer's disease or compared the effects of the diet within and outside of the Mediterranean region. The Mediterranean diet adherence screener (MEDAS) and MEDAS continuous scores were calculated at the baseline visit of the European Prevention of Alzheimer's Dementia Longitudinal Cohort Study (n = 1625). The scores were included in linear regression models to test for associations with hippocampal volume, log-transformed white matter lesion volume, cerebrospinal fluid pTau18, and Aβ42. Higher MEDAS scores were associated with lower log-transformed white matter lesion volume (β: -0.07, standard error [SE]: 0.02, p < 0.001). This association was only seen in the Mediterranean region (β: -0.12, SE: 0.03, p < 0.001). In the non-Mediterranean region, higher MEDAS continuous scores were associated with lower cerebrospinal fluid Aβ42 (β: -68.30, SE: 14.32, p < 0.001). More research is needed to understand the differences in the associations seen with the MedDiet and Alzheimer's disease biomarkers in different European regions.

The role of lifestyle factors in cognitive health and dementia in oldest-old: A systematic review

Oldest-old is the fastest growing segment of society. A substantial number of these individuals are cognitively impaired or demented. Given the lack of a cure, attention is directed to lifestyle interventions that could help alleviate the stress in patients, their families, and society. The aim of this review was to identify lifestyle factors with important roles in dementia prevention in oldest-old. Searches were conducted in PubMed, EMBASE, Scopus and Web of Science. We identified 27 observational cohort studies that met the inclusion criteria. Results showed that eating a healthy diet with plenty of fruits and vegetables, and participation in leisure and physical activities may protect against cognitive decline and cognitive impairment among oldest-old regardless of the APOE genotype. Combined lifestyles may generate multiplicative effects than individual factors. This is the first review known to systematically examine the association between lifestyle and cognitive health in oldest-old. Lifestyle interventions for diet, leisure, or a combination of lifestyles could be beneficial for cognitive function in oldest-old. Interventional studies are warranted to strengthen the evidence.

Association between animal protein sources and risk of neurodegenerative diseases: a systematic review and dose-response meta-analysis

CONTEXT

Current findings about the differential effects of various sources of dietary animal protein on the risk of neurodegenerative diseases are contradictory.

OBJECTIVE

The current meta-analysis was conducted to investigate the associations between intake of dietary animal protein sources and the risk of neurodegenerative diseases.

DATA SOURCES

PubMed, Scopus, Web of Science, and Google Scholar databases were searched systematically until October 2021.

DATA EXTRACTION

Prospective cohort studies exploring the association between consumption of animal protein sources and risk of neurodegenerative diseases in the general population were included. Among 10 571 identified studies, 33 prospective cohort studies met the eligibility criteria.

DATA ANALYSIS

Dietary fish consumption was associated with a reduced risk of Alzheimer's disease (RR = 0.75; 95%CI, 0.57-0.97), dementia (RR = 0.84; 95%CI, 0.75-0.93), and cognitive impairment (RR = 0.85; 95%CI, 0.81-0.95). The risk of developing Parkinson's disease was significantly higher among those in the highest vs the lowest intake categories of total dairy (RR = 1.49; 95%CI, 1.06-2.10) and milk (RR = 1.40; 95%CI, 1.13-1.73). Moreover, dietary intake of total dairy (RR = 0.89; 95%CI, 0.80-0.99), total meat (RR = 0.72; 95%CI, 0.57-0.90), and poultry (RR = 0.82; 95%CI, 0.68-0.99) was significantly associated with a lower risk of cognitive impairment. A linear dose-response meta-analysis revealed that each 200-g increase in total daily dairy intake was associated with an 11% higher risk of Parkinson's disease and a 12% lower risk of cognitive impairment. Furthermore, there was a strong linear association between fish consumption and reduced risk of dementia.

CONCLUSION

Dairy consumption is associated with an increased risk of Parkinson's disease, but a higher intake of fish may be associated with lower risk of neurodegenerative disease. Future well-controlled, randomized clinical trials are essential to validate the present findings.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021281887.

Longitudinal Dietary Trajectories With Cognitive and Psychosocial Well-Being in Chinese Adults Aged 85 Years and Older in Singapore

Background and Objectives

Studies on longitudinal trajectories of diet and the influence on aging in older adults are limited. We characterized diet quality trajectories over the past 2 decades among adults aged ≥85 years and examined their associations with cognitive and psychosocial outcomes.

Research Design and Methods

We used data from 861 participants in the population-based Singapore Chinese Health Study. Dietary intakes were assessed at baseline (mean age [range]: 65 [60-74] years) and at follow-ups 3 (85 [81-95]) and 4 (88 [85-97]) years. Diet quality was measured by adherence to the Dietary Approaches to Stop Hypertension pattern, and group-based trajectory modeling was used to derive diet quality trajectories. At Follow-up 4, we assessed cognition using the Singapore-modified Mini-Mental State Examination, depressive symptoms using the 15-item Geriatric Depression Scale, social engagement, and self-rated health. Multivariable logistic regression models examined associations of diet quality trajectories with these outcomes.

Results

About 49.7% had a trajectory with consistently low diet quality scores, whereas 50.3% had a trajectory with consistently high diet quality scores. Compared to the "consistently low" trajectory, the "consistently high" trajectory had 29% and 26% lower likelihoods of cognitive impairment and depressive symptoms, respectively (odds ratio, 95% confidence interval: 0.71 [0.51, 0.99] and 0.74 [0.55, 0.99], respectively); as well as 47% higher likelihood of social engagement (1.47 [1.09, 1.98]). No statistically significant association was observed between the trajectories and self-rated health.

Discussion and Implications

Maintaining high diet quality throughout the older adult life course was associated with better cognitive and psychosocial well-being in adults aged ≥85 years.

Prospective Study of Diet Quality and the Risk of Dementia in the Oldest Old

This study examined the associations between overall diet quality and the risk of dementia in a rural cohort among the oldest old. Included in this prospective cohort study were 2232 participants aged ≥ 80 years and dementia-free at the baseline according to the Geisinger Rural Aging Study (GRAS), a longitudinal cohort in rural Pennsylvania. In 2009, diet quality was assessed by a validated dietary screening tool (DST). Incident cases of dementia during 2009-2021 were identified using diagnosis codes. This approach was validated by a review of electronic health records. Associations between diet quality scores and the incidence of dementia were estimated using the Cox proportional hazards models, adjusted for potential confounders. Across a mean of 6.90 years of follow-up, we identified 408 incident cases of all-cause dementia. Having a higher diet quality was not significantly associated with a lower risk for incidents of all-cause dementia (adjusted HR for the highest compared with the lowest tertile: 1.01, 95% CI: 0.79, 1.29, P-trend = 0.95). Similarly, we did not observe a significant association between diet quality and altered risks of Alzheimer's disease and other forms of dementia. Overall, having a higher diet quality was not significantly associated with a lower risk of dementia among the oldest old during the full follow-up.

Whole Dietary Patterns, Cognitive Decline and Cognitive Disorders: A Systematic Review of Prospective and Intervention Studies

Dementia prevalence is a global public health concern. Adherence towards a healthy dietary pattern (DP) may reduce the risk of cognitive decline and dementia. This narrative systematic review aimed to synthesise prospective and intervention study data to evaluate the impact of a-posteriori and a-priori derived DPs on cognitive ageing, from cognitive decline to incident dementia. Ninety-three studies were included: 83 prospective studies and 10 randomised controlled trials (RCT). Most prospective studies (77%) examined a-priori DPs, with the Mediterranean diet examined most frequently. A total of 52% of prospective and 50% of RCTs reported a protective relationship between 'healthy' DPs and global cognitive decline. Overall, 59% of prospective studies reported positive associations between healthy DPs and risk of cognitive disorder. Incident cognitive disorder was examined by only one intervention study (subgroup analysis) which reported a beneficial effect of a low-fat diet on risk of probable dementia in women. Unhealthy DPs were examined less frequently (n = 17; 21%), with 41% of these studies reporting associations between adherence and poorer cognitive outcomes. Overall, there were mixed results for healthy and unhealthy DPs on cognition, likely due to between-study heterogeneity. Standardisation of diet exposure and cognitive outcome measurement would help to reduce this. Future research would benefit from investigating effects of culturally appropriate DPs on individual cognitive domains and incident cognitive disorders in diverse and high-risk populations.

Frequency and correlates of mild cognitive impairment and dementia among the oldest old - Evidence from the representative "Survey on quality of life and subjective well-being of the very old in North Rhine-Westphalia (NRW80+)"

OBJECTIVES

Since there is limited knowledge with regard to the frequency and correlates of mild cognitive impairment and dementia among the oldest old based on large representative data (including institutionalized individuals), our objective was to fill this research gap.

METHODS

For our study, data came from the representative "Survey on quality of life and subjective well-being of the very old in North Rhine-Westphalia (NRW80+)". This study included community-dwelling and institutionalized individuals aged 80 years and over (n = 1,173, mean age: 86 years) residing in the most populous state of Germany (North Rhine-Westphalia). The DemTect was used to quantify cognitive impairment (i.e., probable mild cognitive impairment and probable dementia).

RESULTS

Overall, 73.1% of the individuals were not cognitively impaired, 17.0% of the individuals had probable mild cognitive impairment and 9.9% of the individuals had probable dementia. Compared to individuals without cognitive impairment, individuals with probable mild cognitive impairment were more likely to be male, live in an institutionalized setting, have a lower educational level, have a smaller network size, and have lower functional abilities. Moreover, compared to individuals without cognitive impairment, individuals with probable dementia were more likely to be older, live in an institutionalized setting, have a lower educational level, have a smaller network size, not be multimorbid, and have lower functional abilities.

CONCLUSIONS

Our study identified several sociodemographic and health-related factors which are associated with probable mild cognitive impairment and probable dementia among the oldest old. This knowledge may help to address individuals at risk for mild cognitive impairment and dementia.