Dementia is one of the most feared medical conditions worldwide; it represents a significant global challenge to health and social care.^1,2 Recent evidence suggests that dementia rates have decreased in the last few decades in the United Kingdom and other parts of Western Europe.^3-5 Similarly, in the United States, the Framingham Heart Study has shown that age-specific incidence rates of dementia have decreased by almost 20% within the last few decades, and the greatest declines were apparent in individuals with higher educational attainment relative to more basic educational attainment.⁶

Several risk factors contribute to dementia, but the role of obesity remains unclear. This study investigated whether increased body weight or central obesity were associated with a higher risk of developing dementia in a representative sample of older English adults. We studied 6582 participants from the English Longitudinal Study of Ageing (ELSA) who were aged ≥50 years and were dementia-free at baseline, that being either wave 1 (2002–2003) for study members who started at wave 1, or at either wave 2 (2004–2005) or 4 (2008–2009) for those who began the study as refreshment samples. Body mass index (BMI) was measured at baseline and categorized into normal weight (18.5–24.9 kg/m²), overweight (25–29.9 kg/m²) and obese (≥30 kg/m²). Central obesity was defined as a waist circumference (WC) >88 cm for women and >102 cm for men. Cumulative incidence of dementia was ascertained based on physician-diagnosed dementia, an overall score >3.38 on the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) and Hospital Episodes Statistics (HES) data at every ELSA wave from baseline until wave 8 (2016–2017). Cox proportional hazards models were used to assess the association between baseline BMI levels or abdominal obesity in relation to dementia incidence during the mean follow-up period of 11 years. From the overall sample, 6.9% (n = 453) of participants developed dementia during the follow-up period of maximum 15 years (2002–2017). Compared with participants with normal weight, those who were obese at baseline had an elevated risk of dementia incidence [hazard ratio (HR) = 1.34, 95% confidence interval (CI) 1.07–1.61] independent of sex, baseline age, apolipoprotein E-ε4 (APOE-ε4), education, physical activity, smoking and marital status. The relationship was slightly accentuated after additionally controlling for hypertension and diabetes (HR = 1.31, 95% CI 1.03–1.59). Women with central obesity had a 39% greater risk of dementia compared with non-central obese women (HR = 1.39, 95% CI 1.12–1.66). When compared with a normal BMI and WC group, the obese and high WC group had 28% (HR = 1.28, 95% CI 1.03–1.53) higher risk of dementia. Our results suggest that having an increased body weight or abdominal obesity are associated with increased dementia incidence. These findings have significant implications for dementia prevention and overall public health.

Differences in dementia risk across the gradient of socioeconomic status (SES) exist, but their determinants are not well understood. This study investigates whether health conditions and lifestyle-related risk factors explain the SES inequalities in dementia risk. 6,346 participants from the English Longitudinal Study of Ageing were followed up from 2008/2009 until 2014/2015. We used Cox regression adjusted for age, gender, wealth/education, and clustering at the household level to examine the association between SES markers (wealth, education) and time to dementia in a structural equation model including potential mediation or effect modification by a weighted compound score of twelve modifiable risk and protective factors for dementia ('LIfestyle for BRAin health' (LIBRA) score). During a median follow-up of 6 years, 192 individuals (3.0%) developed dementia. LIBRA scores decreased with increasing wealth and higher educational level. A one-point increase in the LIBRA score was associated with a 13% increase in dementia risk (hazard ratio (HR) = 1.13, 95% confidence interval 1.07-1.19). Higher wealth was associated with a decreased dementia risk (HR = 0.58, 0.39-0.85). Mediation analysis showed that 52% of the risk difference between the highest and lowest wealth tertile was mediated by differences in LIBRA (indirect effect: HR = 0.75, 0.66-0.85). Education was not directly associated with dementia (HR = 1.05, 0.69-1.59), but was a distal risk factor for dementia by explaining differences in wealth and LIBRA scores (indirect effect high education: HR = 0.92, 0.88-0.95). Socioeconomic differences in dementia risk can be partly explained by differences in modifiable health conditions and lifestyle factors.

Importance: Cognitive decline and depressive symptoms often co-occur among older adults, and they share several mechanisms. Despite the fact that cognitive dysfunction has been linked to increased depressive symptoms, the directionality of this association remains unclear.Objective: To examine whether there is a bidirectional association between depressive symptoms and cognitive function in English adults aged 50 years or older throughout a 16-year follow-up period.Design, Setting, and Participants: This cohort study included a nationally representative sample of community-dwelling English adults aged 50 years or older. The current analysis included 8268 eligible participants with relevant data. These participants were examined every other year from 2002 and 2003 until 2018 and 2019, resulting in a follow-up period of up to 16 years. Data were analyzed from July to November 2023.Main Outcomes and Measures: The bivariate dual change score models were used to estimate the multivariable associations between depressive symptoms and cognitive function, which were interchangeably used as exposures and outcomes. Cognitive measures include memory and verbal fluency tests, while the Center for Epidemiologic Studies Depression Scale evaluated depressive symptoms.Results: The study population of 8268 participants had a mean (SD) age of 64 (10) years at the study baseline, and 4517 participants (55%) were female. Higher depressive symptoms were cross-sectionally associated with poorer memory (β intercept, −0.018; standard error [SE], 0.004; P < .001) and verbal fluency (β intercept, −0.009; SE, 0.004; P = .02) at study baseline. A steeper linear change in depressive symptoms was associated with an accelerated memory change (β intercept, −0.253; SE, 0.079; P = .001), and a linear change in memory was associated with an acceleration in depressive symptoms over time (β intercept, 0.016; SE, 0.006; P = .005). This bidirectional change was not observed with verbal fluency.Conclusions and Relevance: In this study, greater depressive symptoms were associated with poorer memory at the study baseline and steeper memory change over time. A gradual linear change in depressive symptoms contributed to accelerated memory loss and vice versa, suggesting that psychological mood and memory performance are intrinsically associated.

Objectives: To determine whether hearing loss is associated with incident physician‐diagnosed dementia in a representative sample. Design: Retrospective cohort study. Setting: English Longitudinal Study of Ageing. Participants: Adults aged 50 and older. Measurements: Cross‐sectional associations between self‐reported (n = 7,865) and objective hearing measures (n = 6,902) and dementia were examined using multinomial‐logistic regression. The longitudinal association between self‐reported hearing at Wave 2 (2004/05) and cumulative physician‐diagnosed dementia up to Wave 7 (2014/15) was modelled using Cox proportional hazards regression. Results: After adjustment for potential confounders, in cross‐sectional analysis, participants who had self‐reported or objective moderate and poor hearing were more likely to have a dementia diagnosis than those with normal hearing (self‐reported: odds ratio OR = 1.6, 95% CI = 1.1–2.4 moderate hearing; OR = 2.6, 95% CI = 1.7–3.9 poor hearing, objective: OR = 1.6, 95% CI = 1.0–2.8 moderate hearing; OR = 4.4, 95% CI = 1.9–9.9 poor hearing). Longitudinally, the hazard of developing dementia was 1.4 (95% CI = 1.0–1.9) times as high in individuals who reported moderate hearing and 1.6 (95% CI = 1.1–2.0) times as high in those who reported poor hearing. Conclusion: Older adults with hearing loss are at greater risk of dementia than those with normal hearing. These findings are consistent with the rationale that correction of hearing loss could help delay the onset of dementia, or that hearing loss itself could serve as a risk indicator for cognitive decline.