Weili Xu

Diabetes mellitus and risk of dementia in the Kungsholmen project A 6-year follow-up study

Background: Research on diabetes mellitus as a risk factor for dementia and its main subtypes has produced conflicting results. The authors investigated the relationship between diabetes mellitus and risk of dementia, Alzheimer disease (AD), and vascular dementia (VaD). Methods: A dementia-free cohort of 1,301 community dwellers aged 75 years and older in Stockholm, Sweden, was longitudinally examined twice over 6 years to detect dementia cases (Diagnostic and Statistical Manual of Mental Disorders–III-R diagnostic criteria). Cox proportional hazards models were used to analyze the data with adjustment for several potential confounders. Results: During the 5,584 person-years of follow-up, 350 subjects developed dementia, including 260 AD and 49 VaD cases. Diabetes mellitus was associated with hazard ratios (HR) of 1.5 (95% CI 1.0 to 2.1, p = 0.04) for dementia, 2.6 (95% CI 1.2 to 6.1) for VaD, and 1.3 (95% CI 0.9 to 2.1) for AD. Patients who were treated with oral antidiabetic medications had HRs of 1.7 (95% CI 1.0 to 2.8, p = 0.04) for dementia and 3.6 (95% CI 1.3 to 9.5) for VaD. There were significant interactions of diabetes with severe systolic hypertension (≥180 mm Hg) on dementia and its main subtypes, and of diabetes with heart disease on VaD. Conclusions: Diabetes mellitus increases the risk of dementia, and VaD in particular, in very old people. The risk for dementia and VaD is especially high when diabetes mellitus occurs together with severe systolic hypertension or heart disease.

Midlife overweight and obesity increase late-life dementia risk A population-based twin study

Objective: The relation of overweight to dementia is controversial. We aimed to examine the association of midlife overweight and obesity with dementia, Alzheimer disease (AD), and vascular dementia (VaD) in late life, and to verify the hypothesis that genetic and early-life environmental factors contribute to the observed association. Methods: From the Swedish Twin Registry, 8,534 twin individuals aged ≥65 (mean age 74.4) were assessed to detect dementia cases (DSM-IV criteria). Height and weight at midlife (mean age 43.4) were available in the Registry. Data were analyzed as follows: 1) unmatched case-control analysis for all twins using generalized estimating equation (GEE) models and 2) cotwin matched case-control approach for dementia-discordant twin pairs by conditional logistic regression taking into account lifespan vascular disorders and diabetes. Results: Among all participants, dementia was diagnosed in 350 subjects, and 114 persons had questionable dementia. Overweight (body mass index [BMI] >25–30) and obesity (BMI >30) at midlife were present in 2,541 (29.8%) individuals. In fully adjusted GEE models, compared with normal BMI (20–25), overweight and obesity at midlife were related to dementia with odds ratios (ORs) (95% CIs) of 1.71 (1.30–2.25) and 3.88 (2.12–7.11), respectively. Conditional logistic regression analysis in 137 dementia-discordant twin pairs led to an attenuated midlife BMI-dementia association. The difference in ORs from the GEE and the matched case-control analysis was statistically significant (p = 0.019). Conclusions: Both overweight and obesity at midlife independently increase the risk of dementia, AD, and VaD. Genetic and early-life environmental factors may contribute to the midlife high adiposity–dementia association.

Mid- and late-life diabetes in relation to the risk of dementia: a population-based twin study.

OBJECTIVE—We aimed to verify the association between diabetes and the risk of dementia, Alzheimers disease, and vascular dementia in twins and to explore whether genetic and early-life environmental factors could contribute to this association. RESEARCH DESIGN AND METHODS—This study included 13,693 twin individuals aged ≥65 years. Dementia was diagnosed according to DSM-IV (Diagnostic Manual of Mental Disorders, 4th ed.) criteria. Information on diabetes was collected from the inpatient registry and self- or informant-reported history of diabetes. Data were analyzed following two strategies: 1) unmatched case-control analysis for all participants using generalized estimating equation (GEE) models and 2) cotwin matched case-control analysis for dementia-discordant twin pairs using conditional logistic regression. RESULTS—Of all participants, 467 were diagnosed with dementia, including 292 with Alzheimers disease and 105 with vascular dementia, and an additional 170 were diagnosed with questionable dementia. Diabetes was present in 1,396 subjects. In GEE models, diabetes was associated with adjusted odds ratios (ORs) (95% CI) of 1.89 (1.51–2.38) for dementia, 1.69 (1.16–2.36) for Alzheimers disease, and 2.17 (1.36–3.47) for vascular dementia. Compared with late-life diabetes (onset age ≥65 years), the risk effect of mid-life diabetes (onset age <65 years) on dementia was stronger. Conditional logistic analysis of 210 dementia-discordant twin pairs led to ORs of 2.41 (1.05–5.51) and 0.68 (0.30–1.53) for dementia related to mid- and late-life diabetes, respectively. CONCLUSIONS—Diabetes increases the risk of Alzheimer disease and vascular dementia. The risk is stronger when diabetes occurs at mid-life than in late life. Genetic and early-life environmental factors might contribute to the late-life diabetes–dementia association but could not account for the mid-life diabetes–dementia association.

The Effect of Borderline Diabetes on the Risk of Dementia and Alzheimer’s Disease

To verify the hypothesis that borderline diabetes may increase the risk of dementia and Alzheimer’s disease, a community-based cohort of 1,173 dementia- and diabetes-free individuals aged ≥75 years was longitudinally examined three times to detect patients with dementia and Alzheimer’s disease (Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition criteria). Borderline diabetes was defined as a random plasma glucose level of 7.8–11.0 mmol/l. Data were analyzed using Cox proportional hazards models. During the 9-year follow-up, 397 subjects developed dementia, including 307 Alzheimer’s cases. At baseline, 47 subjects were identified with borderline diabetes. Borderline diabetes was associated with adjusted hazard ratios (95% CIs) of 1.67 (1.04–2.67) for dementia and 1.77 (1.06–2.97) for Alzheimer’s disease; the significant associations were present after additional adjustment for future development of diabetes. Stratified analysis suggested a significant association between borderline diabetes and Alzheimer’s disease only among noncarriers of APOE ε4 allele. There was an interaction between borderline diabetes and severe systolic hypertension on the risk of Alzheimer’s disease (P = 0.04). We conclude that borderline diabetes is associated with increased risks of dementia and Alzheimer’s disease; the risk effect is independent of the future development of diabetes. Borderline diabetes may interact with severe systolic hypertension to multiply the risk of Alzheimer’s disease.

Accelerated Progression from Mild Cognitive Impairment to Dementia in People with Diabetes

OBJECTIVE The effect of diabetes on mild cognitive impairment (MCI) and its conversion to dementia remains controversial. We sought to examine whether diabetes and pre-diabetes are associated with MCI and accelerate the progression from MCI to dementia. RESEARCH DESIGN AND METHODS In the Kungsholmen Project, 963 cognitively intact participants and 302 subjects with MCI (120 with amnestic MCI [aMCI ] and 182 with other cognitive impairment no dementia [oCIND]) age ≥75 years were identified at baseline. The two cohorts were followed for 9 years to detect the incident MCI and dementia following international criteria. Diabetes was ascertained based on a medical examination, hypoglycemic medication use, and random blood glucose level ≥11.0 mmol/l. Pre-diabetes was defined as random blood glucose level of 7.8–11.0 mmol/l in diabetes-free participants. Data were analyzed using standard and time-dependent Cox proportional-hazards models. RESULTS During the follow-up period, in the cognitively intact cohort, 182 people developed MCI (42 aMCI and 140 oCIND), and 212 developed dementia. In the MCI cohort, 155 subjects progressed to dementia, the multi-adjusted hazard ratio (95% CI) of dementia was 2.87 (1.30–6.34) for diabetes, and 4.96 (2.27–10.84) for pre-diabetes. In a Kaplan-Meier survival analysis, diabetes and pre-diabetes accelerated the progression from MCI to dementia by 3.18 years. Diabetes and pre-diabetes were neither cross-sectionally nor longitudinally associated with MCI. CONCLUSIONS Diabetes and pre-diabetes substantially accelerate the progression from MCI to dementia, and anticipate dementia occurrence by more than 3 years in people with MCI. The association of diabetes with the development of MCI is less evident in old people.

The Obesity Related Gene, FTO, Interacts with APOE, and is Associated with Alzheimer's Disease Risk: A Prospective Cohort Study

The FTO gene has been shown to have a small but robust effect on body mass index (BMI) and to increase the risk for diabetes. Both high BMI and diabetes are vascular risk factors that might play a role in the development of Alzheimers disease (AD) and dementia. Thus, our aim was to explore the impact of FTO on AD and dementia risk. Nine years of follow-up data was gathered from the Kungsholmen project, a prospective population-based study on 1,003 persons without dementia. Cox-regression models were used to assess the relative risks of developing AD and dementia (DSM-III-R criteria) according to FTO genotypes (rs9939609), taking into account APOE, physical inactivity, BMI, diabetes, and cardiovascular disease (CVD). Compared to carriers of the FTO TT-genotype, AA-carriers had a higher risk for AD (RR 1.58, 95% CI: 1.11-2.24) and for dementia (RR 1.48, 95% CI: 1.09-2.02) after adjustment for age, gender, education, and APOE genotype. This effect remained after additional adjustment for physical inactivity, BMI, diabetes, and CVD. An interaction between FTO and APOE was found, with increased risk for dementia for those carrying both FTO AA and APOE ϵ4. Importantly, the effect of the AA-genotype on dementia/AD risk seems to act mostly through the interaction with APOE ϵ4. Our findings suggest that the FTO AA-genotype increases the risk for dementia, and in particular AD, independently of physical inactivity, BMI, diabetes, and CVD measured at baseline. Our results are in line with the recently reported association between FTO and reduced brain volume in cognitively healthy subjects.

Vascular and Psychosocial Factors in Alzheimer's Disease: Epidemiological Evidence Toward Intervention

Alzheimers disease (AD), the most common cause of dementia, is posing serious threat to public health and health care system in both developed and developing nations due to a rapid increase in the aging population. Identification of etiological factors for AD and active implementation of interventions targeting those modifiable factors that may prevent or postpone clinical onset of the dementing disorder will provide an opportunity to cope with this challenge. Multidisciplinary research involving epidemiology, neuropathology, and neuroimaging has provided moderately strong evidence supporting the role of vascular factors and related disorders (e.g., midlife high blood pressure and obesity, diabetes, cerebral microvascular lesions, and smoking) as risk factors and the possible role of psychosocial factors (e.g., high educational achievements, mentally-stimulating activity, social engagement, and physical exercise) as protective factors in the development and clinical manifestation of the dementia syndrome, including AD. The implementation of long-term, multidomain interventions designed for the modification of multiple vascular risk factors and the maintenance of socially-integrated lifestyles and mentally-stimulating activities is expected to postpone the clinical onset of AD and dementia, and thus, substantially reduce the burden of the disease at both the individual and societal levels.

Cognitive decline, dietary factors and gut-brain interactions

Cognitive decline in elderly people often derives from the interaction between aging-related changes and age-related diseases and covers a large spectrum of clinical manifestations, from intact cognition through mild cognitive impairment and dementia. Epidemiological evidence supports the hypothesis that modifiable lifestyle-related factors are associated with cognitive decline, opening new avenues for prevention. Diet in particular has become the object of intense research in relation to cognitive aging and neurodegenerative disease. We reviewed the most recent findings in this rapidly expanding field. Some nutrients, such as vitamins and fatty acids, have been studied longer than others, but strong scientific evidence of an association is lacking even for these compounds. Specific dietary patterns, like the Mediterranean diet, may be more beneficial than a high consumption of single nutrients or specific food items. A strong link between vascular risk factors and dementia has been shown, and the association of diet with several vascular and metabolic diseases is well known. Other plausible mechanisms underlying the relationship between diet and cognitive decline, such as inflammation and oxidative stress, have been established. In addition to the traditional etiological pathways, new hypotheses, such as the role of the intestinal microbiome in cognitive function, have been suggested and warrant further investigation.

An active lifestyle postpones dementia onset by more than one year in very old adults

The purpose of this study was to test the hypothesis that an active lifestyle delays age at dementia onset. This study included 388 incident dementia cases (DSM-III-R criteria) that developed over a 9-year follow-up period among 1,375 baseline dementia-free community dwellers with good cognitive function (MMSE >23) (mean age = 81.2) from the Kungsholmen Project. An active lifestyle was defined as participation in mental, physical, or social activity. We used linear regression models to estimate influence of baseline active lifestyle on age at onset of incident dementia and general linear models to estimate mean age at dementia onset. Age at onset of dementia was significantly older in persons who had higher levels of participation in mental, physical, or social activity (β: 0.18, 0.29 and 0.23 respectively, p < 0.001 for all the activities) independent of education, medical condition, functional status, and other confounders including APOE. When the three types of activities were integrated into an index, we found that the broader the spectrum of participation in the activities, the later the onset of disease (β = 0.93, p = 0.01 for participating in two activities, and β = 1.42, p < 0.001 for three activities). There were 17 months difference in mean age at dementia onset between the inactive group and the most active group. An active lifestyle operates as a protective factor for dementia by delaying the clinical onset of the disease. These findings highlight the relevance of encouraging old adults to have active lifestyles, which could have a great impact on public health.

Vascular Risk Profiles for Dementia and Alzheimer's Disease in Very Old People: A Population-Based Longitudinal Study

Numerous studies have linked individual vascular factors to dementia including Alzheimers disease (AD). We investigated different vascular risk profiles in relation to dementia and AD among very old people. A standardized follow-up procedure was applied three times to a dementia-free cohort (n=1270, age >or= 75) over a nine-year period to detect dementia and AD cases using the DSM-III-R criteria. We examined two vascular risk profiles, which were scored by counting the number of corresponding vascular factors: 1) atherosclerotic profile included systolic pressure >or= 160 mmHg, diabetes/prediabetes, and stroke; and 2) cerebral hypoperfusion profile constituted diastolic pressure < 70 mmHg, pulse pressure < 70 mmHg, and heart failure. Data were analyzed with Cox proportional-hazards models controlling for major potential confounders. During the 6406 person-years of follow-up, 428 subjects developed dementia, including 328 AD cases. All components of vascular profiles were significantly or marginally associated with increased dementia risk. The risk of dementias was increased with increasing score of both risk profiles (p for trend <or= 0.001); subjects with a score >or= 2 in either profile had an approximately twofold-increased risk for dementia and AD. These data suggest that aggregation of atherosclerotic- and hypoperfusion-related vascular factors increases the risk of dementia in very old people. Severe cerebral atherosclerosis and insufficient perfusion are involved in the development of dementia including AD.