Serum sodium, cognition and incident dementia in the general population.

BACKGROUND: Low serum sodium may be associated with cognitive impairment and dementia in the general population, but the data remain inconclusive. Therefore, we aimed to determine the association of low serum sodium with cognitive function and incident dementia in the general population. METHODS: Participants from a prospective population-based cohort were eligible if data on serum sodium (collected between 1997 and 2008), dementia prevalence and dementia incidence were available (follow-up until 2018). Global cognitive function was assessed with the Mini-Mental State Examination (MMSE) and the general cognitive factor (G-factor, derived from principal component analysis of individual tests). Linear regression and Cox proportional-hazards models were used to assess associations of standardised continuous and categorised low serum sodium (mean - 1.96*SD: cut-off of 137 mmol/L) with overall cognitive function and incident dementia, respectively. RESULTS: In all, 8,028 participants free of dementia at baseline (mean age 63.6 years, 57% female, serum sodium 142 ± 2 mmol/L), including 217 participants with low serum sodium, were included. Cross-sectionally, continuous serum sodium and/or low serum sodium were not associated with the MMSE or G-factor. However, participants with low serum sodium performed worse on the Stroop and Purdue Pegboard tests. During a median follow-up of 10.7 years, 758 subjects developed dementia. Continuous serum sodium (hazard ratio (HR) 0.98, 95% confidence interval (CI) 0.92;1.05) and low serum sodium (HR 1.27, 95% CI 0.90;1.79) were not associated with a higher risk of incident dementia. CONCLUSION: We identified no significant associations of low serum sodium with overall cognitive functioning and risk of dementia. However, low serum sodium-including levels above the clinical cut-off for hyponatremia-was associated with impairments in selected cognitive domains including attention and psychomotor function.

Adiposity in the older population and the risk of dementia: The Rotterdam Study.

INTRODUCTION: We determined associations of total and regional adiposity with incident dementia among older adults. METHODS: Within the population-based Rotterdam Study, adiposity was measured as total, android, and gynoid fat mass using dual-energy X-ray absorptiometry in 3408 men and 4563 women, every 3 to 6 years between 2002 and 2016. Incident dementia was recorded until 2020. RESULTS: Higher adiposity measures were associated with a decreased risk of dementia in both sexes. After excluding the first 5 years of follow-up, only the association of gynoid fat among women remained significant (hazard ratio 0.85 [95% confidence interval 0.75-0.97] per standard deviation increase). No major differences in trajectories of adiposity measures were observed between dementia cases and dementia-free controls. DISCUSSION: Higher total and regional fat mass related to a decreased risk of dementia. These results may be explained by reverse causality, although a protective effect of adiposity cannot be excluded. HIGHLIGHTS: Total and regional adiposity were assessed using dual-energy X-ray absorptiometry scans in 7971 older adults. All adiposity measures were associated with a decreased risk of dementia. The results suggest a beneficial effect of gynoid fat on the risk of dementia in women. Reverse causation and competing risk may explain these inverse associations.

Season of birth and the risk of dementia in the population-based Rotterdam Study.

Early-life environmental factors have been suggested in the pathophysiology of dementia. Season of birth has previously been used as a proxy for these external exposures. We investigated the link between season of birth and the risk of dementia and further explored underlying pathways by studying structural brain changes on MRI. From the Dutch, population-based Rotterdam Study, 12,964 participants born between 1887 and 1960 were followed between 1990 and 2018 for dementia. Cox regression was conducted to assess the association between season of birth and dementia. In addition, we distinguished between mild and cold winters. The association of season of birth with structural brain markers on MRI was examined in 5237 participants. The risk of dementia in participants born in winter and fall was higher than of those born in summer (hazard ratio (HR) 1.15 [95% confidence interval (CI) 1.01-1.31] for winter and HR 1.17 [95% CI 1.01-1.33] for fall), especially for Alzheimer's disease (HR 1.23 [1.06-1.43] for winter and HR 1.15 [95% CI 0.99-1.35] for fall). The risk was particularly increased for participants born in a cold winter. Except for slightly lower hippocampus in fall born participants (ß - 0.03; 95% CI - 0.06 to 0.00), we did not find associations with brain imaging markers. In conclusion, winter and fall births were associated with a higher incidence of dementia, especially of AD. We did not find evidence for structural brain changes as an underlying mechanism.

Skin autofluorescence, reflecting accumulation of advanced glycation end products, and the risk of dementia in a population-based cohort.

Conditions such as hyperglycemia and oxidative stress lead to the formation of advanced glycation end products (AGEs), which are harmful compounds that have been implicated in dementia. Within the Rotterdam Study, we measured skin AGEs as skin autofluorescence, reflecting long-term accumulation of AGEs, and determined their association with the risk of dementia and with brain magnetic resonance imaging (MRI) measures. Skin autofluorescence was measured between 2013 and 2016 in 2922 participants without dementia. Of these, 1504 also underwent brain MRI, on which measures of brain atrophy and cerebral small vessel disease were assessed. All participants were followed for the incidence of dementia until 2020. Of 2922 participants (mean age 72.6 years, 57% women), 123 developed dementia. Higher skin autofluorescence (per standard deviation) was associated with an increased risk of dementia (hazard ratio 1.21 [95% confidence interval 1.01-1.46]) and Alzheimer's disease (1.19 [0.97-1.47]), independently of age and other studied potential confounders. Stronger effects were seen in apolipoprotein E (APOE) ε4 carriers (1.34 [0.98-1.82]) and in participants with diabetes (1.35 [0.94-1.94]). Participants with higher skin autofluorescence levels also had smaller total brain volumes and smaller hippocampus volumes on MRI, and they had more often lacunes. These results suggest that AGEs may be involved in dementia pathophysiology.

Cerebral Small Vessel Disease in Population-Based Research: What are We Looking at - and What not?

Cerebral small vessel disease (CSVD) is considered as one of the main causes of cognitive decline and dementia. However, despite extensive research, the pathogenesis of CSVD and the mechanisms through which CSVD leads to its clinical manifestations remain largely unclear. The challenging in vivo quantification of CSVD hampers progress in further unraveling the pathogenesis and pathophysiology of CSVD. Currently, markers of CSVD are mainly brain abnormalities attributed to CSVD, but these are limited in reflecting morphological and functional changes of the microvasculature. We describe aspects of CSVD that are reflected by currently used techniques and those that are still insufficiently captured.

Association of Bone Mineral Density and Dementia: The Rotterdam Study.

BACKGROUND AND OBJECTIVES: Low bone mineral density (BMD) and dementia commonly co-occur in older individuals, with bone loss accelerating in patients with dementia due to physical inactivity and poor nutrition. However, uncertainty persists over the extent to which bone loss already exists before onset of dementia. Therefore, we investigated how dementia risk was affected by BMD at various skeletal regions in community-dwelling older adults. METHODS: In a prospective population-based cohort study, BMD at the femoral neck, lumbar spine, and total body and the trabecular bone score (TBS) were obtained using dual-energy X-ray absorptiometry in 3,651 participants free from dementia between 2002 and 2005. Persons at risk of dementia were followed up until January 1, 2020. For analyses of the association between BMD at baseline and the risk of incident dementia, we used Cox proportional hazards regression analyses, adjusting for age, sex, educational attainment, physical activity, smoking status, body mass index, systolic and diastolic blood pressure, cholesterol level, high-density lipoprotein cholesterol, history of comorbidities (stroke and diabetes mellitus), and APOE genotype. RESULTS: Among the 3,651 participants (median age 72.3 ± 10.0 years, 57.9% women), 688 (18.8%) developed incident dementia during a median of 11.1 years, of whom 528 (76.7%) developed Alzheimer disease (AD). During the whole follow-up period, participants with lower BMD at the femoral neck (per SD decrease) were more likely to develop all-cause dementia (hazard ratio [HR] total follow-up 1.12, 95% CI 1.02-1.23) and AD (HRtotal follow-up 1.14, 95% CI 1.02-1.28). Within the first 10 years after baseline, the risk of dementia was greatest for groups with the lowest tertile of BMD (femoral neck BMD, HR0-10 years 2.03; 95% CI 1.39-2.96; total body BMD, HR0-10 years 1.42; 95% CI 1.01-2.02; and TBS, HR0-10 years 1.59; 95% CI 1.11-2.28). DISCUSSION: In conclusion, participants with low femoral neck and total body BMD and low TBS were more likely to develop dementia. Further studies should focus on the predictive ability of BMD for dementia.

Adiponectin, Leptin, and Resistin and the Risk of Dementia.

BACKGROUND: Adipokines are hormones secreted by adipose tissue with roles in energy homeostasis and regulation of metabolism. Their dysregulation is suggested to contribute to the increased risk of dementia seen with midlife obesity, but longitudinal studies investigating this are scarce. We determined the association between plasma levels of adiponectin, leptin, and resistin with the risk of dementia. METHODS: We performed a case-cohort study embedded in the prospective, population-based Rotterdam Study. Plasma levels of the adiponectin, leptin, and resistin were measured at baseline (1997-1999) in a random subcohort of 945 participants without dementia, and additionally in 177 participants, who were diagnosed with dementia during follow-up (until January 1, 2018). RESULTS: Higher levels of leptin and resistin were associated with a decreased risk of dementia (adjusted hazard ratio [95% confidence interval] per SD increase of log-transformed values: 0.85 [0.72-1.00] for leptin; 0.82 [0.71-0.95] for resistin). The association of leptin with dementia was further modified by body mass index and by APOE ε4 carrier status. Adiponectin levels were not associated with the risk of dementia. CONCLUSIONS: These findings support the hypothesis that adipokines have a role in the pathophysiology of dementia. Future studies are warranted to confirm the findings and to explore the underlying mechanisms.

MIND diet and the risk of dementia: a population-based study.

BACKGROUND: Adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet has been linked to a decreased risk of dementia, but reverse causality and residual confounding by lifestyle may partly account for this link. We aimed to address these issues by studying the associations over cumulative time periods, which may provide insight into possible reverse causality, and by using both historical and more contemporary dietary data as this could give insight into confounding since historical data may be less affected by lifestyle factors. METHODS: In the population-based Rotterdam Study, dietary intake was assessed using validated food frequency questionnaires in 5375 participants between 1989 and 1993 (baseline I) and in a largely non-overlapping sample in 2861 participants between 2009 and 2013 (baseline II). We calculated the MIND diet score and studied its association with the risk of all-cause dementia, using Cox models. Incident all-cause dementia was recorded until 2018. RESULTS: During a mean follow-up of 15.6 years from baseline I, 1188 participants developed dementia. A higher MIND diet score at baseline I was associated with a lower risk of dementia over the first 7 years of follow-up (hazard ratio (HR) [95% confidence interval (CI)] per standard deviation (SD) increase, 0.85 [0.74, 0.98]), but associations disappeared over longer follow-up intervals. The mean follow-up from baseline II was 5.9 years during which 248 participants developed dementia. A higher MIND diet score at baseline II was associated with a lower risk of dementia over every follow-up interval, but associations slightly attenuated over time (HR [95% CI] for 7 years follow-up per SD increase, 0.76 [0.66, 0.87]). The MIND diet score at baseline II was more strongly associated with the risk of dementia than the MIND diet score at baseline I. CONCLUSION: Better adherence to the MIND diet is associated with a decreased risk of dementia within the first years of follow-up, but this may in part be explained by reverse causality and residual confounding by lifestyle. Further research is needed to unravel to which extent the MIND diet may affect the risk of dementia.

Seasonality of cognitive function in the general population: the Rotterdam Study.

Seasonal variation in cognitive function and underlying cerebral hemodynamics in humans has been suggested, but not consistently shown in previous studies. We assessed cognitive function in 10,276 participants from the population-based Rotterdam Study, aged 45 years and older without dementia, at baseline and at subsequent visits between 1999 and 2016. Seasonality of five cognitive test scores and of a summary measure of global cognition were determined, as well as of brain perfusion. Using linkage with medical records, we also examined whether a seasonal variation was present in clinical diagnoses of dementia. We found a seasonal variation of global cognition (0.05 standard deviations [95% confidence interval: 0.02-0.08]), the Stroop reading task, the Purdue Pegboard test, and of the delayed world learning test, with the best performance in summer months. In line with these findings, there were fewer dementia diagnoses of dementia in spring and summer than in winter and fall. We found no seasonal variation in brain perfusion. These findings support seasonality of cognition, albeit not explained by brain perfusion.

Trajectories of depression and anxiety during the COVID-19 pandemic in a population-based sample of middle-aged and older adults.

The COVID-19 pandemic and the related governmental restrictions have greatly impacted the lives of people worldwide and have been suggested to negatively impact mental health. We describe the trajectories of depressive and anxiety symptoms during the pandemic and their determinants in a large population-based sample of middle-aged and older adults. From April to June 2020, participants of the Rotterdam Study were asked to complete questionnaires including questions on depressive symptoms (Center of Epidemiological Studies Depression Scale, 10 item version) and anxiety symptoms (Hospital Anxiety and Depression Scale, anxiety subscale). We compared depressive and anxiety symptom scores to those before the pandemic and described its trajectories during the pandemic by demographic variables, chronic disease status and pre-pandemic clinically relevant depressive or anxiety symptoms. In total, 6241 participants responded to the questionnaires (mean age [standard deviation] 70.1 years [11.6]; 58% women). Participants more often reported clinically relevant depressive symptoms during than before the pandemic (19% vs. 12%, P < .001), which was similar for clinically relevant anxiety symptoms (17% vs. 12%, P < .001). During the pandemic, depressive symptoms persisted over time while anxiety symptoms improved. Depressive and anxiety symptoms were more common among women, persons living alone, with chronic diseases and with pre-pandemic clinically relevant symptoms, although the trajectories of these symptoms over time were broadly similar for the subgroups. Together, these results suggest that it is important to be aware of long-term depressive symptoms following the COVID-19 pandemic in the general population.

Life expectancy with and without dementia in persons with mild cognitive impairment in the community.

BACKGROUND: Various clinical studies have provided estimates of life expectancy of patients with mild cognitive impairment (MCI) from outpatient clinics, but whether these apply to community-dwelling individuals at home or in primary care is uncertain. METHODS: Within the population-based Rotterdam Study, we studied life expectancy with and without dementia in 648 community-dwelling persons with MCI and 6410 without MCI. Participants aged 60 years and older were assessed for MCI at baseline (2002-2014) and subsequently followed for the onset of dementia and death. We used multistate life tables to determine age-specific life expectancy with and without dementia by sex, educational attainment, and MCI subtype. RESULTS: Total life expectancy for MCI ranged from 21.4 years (95% CI: 19.0-23.6) at age 60 to 2.6 years (1.6-3.6) at age 95. With advancing age, an increasing proportion of these years was lived with dementia (2.9 years [1.8-4.0] at age 60; 1.2 [0.2-2.2] at age 95). Women and higher educated individuals lived longer and lived more years with dementia. No differences in total life expectancy were observed by MCI subtype, although individuals with amnestic MCI lived a larger proportion of those years with dementia. CONCLUSIONS: Prognosis of MCI, in terms of life years lived with and without dementia, is more favorable in the general population than described in prior clinical observations, due likely to a substantial proportion of individuals with MCI in the clinic not seeking medical attention in an earlier stage.

Characterizing Demographic, Racial, and Geographic Diversity in Dementia Research: A Systematic Review.

Importance: For informed decision making on diagnosis and treatment of dementia, physicians and their patients rely on the generalizability of evidence from published studies to clinical practice. However, it is uncertain whether everyday care of elderly patients with dementia is sufficiently captured in contemporary research. Objective: To systematically review contemporary dementia research in terms of study and patient characteristics in order to assess generalizability of research findings. Evidence Review: PubMed was searched for dementia studies published in the top 100 journals in the fields of neurology and neuroscience, geriatrics, psychiatry, and general medicine between September 1, 2018, and August 31, 2019. Two reviewers extracted study characteristics, including setting, number of participants, age at diagnosis, and use of biomarkers. Findings: Among 513 identified studies, 211 (41%) included fewer than 50 individuals with dementia and were excluded. The remaining 302 studies included a median (interquartile range) of 214 patients (98-628) with a mean (SD) age at diagnosis of 74.1 years (8.0). Age at diagnosis differed with study setting. Patients in the 180 clinic-based studies had a mean (SD) age of 71.8 (6.4) years at time of diagnosis compared with 80.6 (4.7) years among patients in the 79 population-based studies (mean difference, 8.8 years; 95% CI, 7.3-10.2). Use of magnetic resonance imaging, positron emission tomography imaging, and cerebrospinal fluid imaging was mostly done in clinic-based studies (80% to 96%) and consequently in relatively young patients (mean [SD] age, 71.6 [5.1] years). A longitudinal design was more common in population-based studies than in clinic-based studies (82 % vs 40%). Most studies originated from North America and Europe (89%), including almost exclusively White participants (among 74 studies [22%] reporting on ethnicity: median [interquartile range], 89% [78-97]). The 3 most studied cohorts represented 21% of all included study populations. Conclusions and Relevance: Contemporary dementia research is limited in terms of racial and geographic diversity and draws largely from clinic-based populations with relatively young patients. Greater inclusivity and deeper phenotyping in unselected cohorts could improve generalizability as well as diagnosis and development of effective treatments for all patients with dementia.

Assessment of Advanced Glycation End Products and Receptors and the Risk of Dementia.

Importance: Advanced glycation end products (AGEs) and their receptor (RAGE) are implicated in the pathophysiological processes of dementia and potentially underlie the association of diabetes with neurodegeneration. However, longitudinal studies examining this association are lacking. Objective: To determine whether markers of the AGE-RAGE system are associated with prevalent and incident dementia and with cognition. Design, Setting, and Participants: In this population-based cohort study including participants from the prospective Rotterdam Study, extracellular newly identified RAGE binding protein (EN-RAGE) and soluble RAGE (S-RAGE) were measured in plasma collected between 1997 and 1999 in a random selection of participants, and additionally in participants with prevalent dementia. Participants without dementia were followed up for dementia until 2016. Skin AGEs, measured as skin autofluorescence, and cognition were measured between 2013 and 2016 in participants without dementia. Data analysis was performed from June 2019 to December 2019. Exposures: EN-RAGE, S-RAGE, and skin autofluorescence. Main Outcomes and Measures: Prevalent and incident dementia and cognition, adjusted for potential confounders, including age, sex, diabetes, educational level, APOE ε4 carrier status, smoking, and estimated glomerular filtration rate. Results: Of 3889 included participants (mean [SD] age, 72.5 [8.9] years; 2187 [56.2%] women), 1021 participants had data on plasma markers (mean [SD] age 73.6 [7.8] years; 564 [55.2%] women), 73 participants had dementia at baseline, and during 10 711 person-years of follow-up, 161 participants developed incident dementia. Compared with low levels, high EN-RAGE level was associated with a higher prevalence of dementia (odds ratio [OR], 3.68 [95% CI, 1.50-8.03]; P = .003), while high S-RAGE level was associated with a lower prevalence of dementia (OR, 0.37 [95% CI, 0.17-0.78]; P = .01). These associations attenuated in a longitudinal setting, with hazard ratios of 0.65 (95% CI, 0.42-1.01) for high EN-RAGE (P = .05) and 1.22 (95% CI, 0.82-1.81) for high S-RAGE (P = .33). Among 2890 participants without dementia (mean [SD] age, 72.5 [9.4] years; 1640 [57%] women), higher skin autofluorescence was associated with lower global cognitive function (adjusted difference in z score per 1-SD higher skin autofluorescence, -0.07 [95% CI, -0.11 to -0.04]), especially among carriers of the APOE ε4 allele (adjusted difference in z score per 1-SD higher skin autofluorescence, -0.15 [95% CI, -0.22 to -0.07]). Conclusions and Relevance: These findings suggest that the AGE-RAGE system is associated with cognitive decline and dementia cross-sectionally but not longitudinally. This indicates either a short-term association or reverse causality. Findings of cross-sectional associations between higher skin autofluorescence and lower cognitive function and an association with APOE status also warrant replication and prospective studies.