Sex differences in biological aging and the association with clinical measures in older adults.

Females live longer than males, and there are sex disparities in physical health and disease incidence. However, sex differences in biological aging have not been consistently reported and may differ depending on the measure used. This study aimed to determine the correlations between epigenetic age acceleration (AA), and other markers of biological aging, separately in males and females. We additionally explored the extent to which these AA measures differed according to socioeconomic characteristics, clinical markers, and diseases. Epigenetic clocks (HorvathAge, HannumAge, PhenoAge, GrimAge, GrimAge2, and DunedinPACE) were estimated in blood from 560 relatively healthy Australians aged ≥ 70 years (females, 50.7%) enrolled in the ASPREE study. A system-wide deficit accumulation frailty index (FI) composed of 67 health-related measures was generated. Brain age and subsequently brain-predicted age difference (brain-PAD) were estimated from neuroimaging. Females had significantly reduced AA than males, but higher FI, and there was no difference in brain-PAD. FI had the strongest correlation with DunedinPACE (range r: 0.21 to 0.24 in both sexes). Brain-PAD was not correlated with any biological aging measures. Significant correlations between AA and sociodemographic characteristics and health markers were more commonly found in females (e.g., for DunedinPACE and systolic blood pressure r = 0.2, p < 0.001) than in males. GrimAA and Grim2AA were significantly associated with obesity and depression in females, while in males, hypertension, diabetes, and chronic kidney disease were associated with these clocks, as well as DunedinPACE. Our findings highlight the importance of considering sex differences when investigating the link between biological age and clinical measures.

Lifestyle Enrichment in Later Life and Its Association With Dementia Risk.

Importance: Lifestyles enriched with socially and mentally stimulating activities in older age may help build cognitive reserve and reduce dementia risk. Objective: To investigate the association of leisure activities and social networks with dementia risk among older individuals. Design, Setting, and Participants: This longitudinal prospective cohort study used population-based data from the ASPREE Longitudinal Study of Older Persons (ALSOP) for March 1, 2010, to November 30, 2020. Community-dwelling individuals in Australia aged 70 years or older who were generally healthy and without major cognitive impairment at enrollment were recruited to the ALSOP study between March 1, 2010, and December 31, 2014. Data were analyzed from December 1, 2022, to March 31, 2023. Exposures: A total of 19 measures of leisure activities and social networks assessed at baseline were classified using exploratory factor analysis. Main Outcomes and Measures: Dementia was adjudicated by an international expert panel according to Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) criteria. Cox proportional hazards regression examined dementia risk over 10 years, adjusting for education, socioeconomic status, and a range of health-related factors. Results: This study included 10 318 participants. Their median age was 73.8 (IQR, 71.6-77.2) years at baseline, more than half (52.6%) were women, and most self-identified as White (98.0%). In adusted analyses, more frequent engagement in adult literacy activities (eg, writing letters or journaling, using a computer, and taking education classes) and in active mental activities (eg, playing games, cards, or chess and doing crosswords or puzzles) was associated with an 11.0% (adjusted hazard ratio [AHR], 0.89 [95% CI, 0.85-0.93]) and a 9.0% (AHR, 0.91 [95% CI, 0.87-0.95]) lower risk of dementia, respectively. To a lesser extent, engagement in creative artistic activities (craftwork, woodwork, or metalwork and painting or drawing) (AHR, 0.93 [95% CI, 0.88-0.99]) and in passive mental activities (reading books, newspapers, or magazines; watching television; and listening to music or the radio) (AHR, 0.93 [95% CI, 0.86-0.99]) was also associated with reduced dementia risk. In contrast, interpersonal networks, social activities, and external outings were not associated with dementia risk in this sample. Conclusions and Relevance: These results suggest that engagement in adult literacy, creative art, and active and passive mental activities may help reduce dementia risk in late life. In addition, these findings may guide policies for geriatric care and interventions targeting dementia prevention for older adults.

Lifetime posttraumatic stress disorder as a predictor of mortality: a systematic review and meta-analysis.

BACKGROUND: Posttraumatic Stress Disorder (PTSD) could potentially increase the risk of mortality, and there is a need for a meta-analysis to quantify this association. This study aims to determine the extent to which PTSD is a predictor of mortality. METHODS: EMBASE, MEDLINE, and PsycINFO were searched systematically on 12th February 2020, with updated searches conducted in July 2021, and December 2022 (PROSPERO CRD42019142971). Studies involving community-dwelling participants with a diagnosis of PTSD or PTSD symptoms, and a comparator group of individuals without PTSD, and which assessed mortality risk, were included. A random-effects meta-analysis was conducted on studies reporting Odds Ratio (OR), Hazard Ratio (HR), and Risk Ratio (RR), and subgroup analysis was also performed by age, sex, type of trauma experienced, PTSD diagnosis, and cause of death. RESULTS: A total of 30 eligible studies of mostly good methodological quality were identified, with a total of more than 2.1 million participants with PTSD. The majority of studies involved male-dominated, veteran populations. PTSD was associated with a 47% (95% CI: 1.06-2.04) greater risk of mortality across six studies that reported OR/RR, and a 32% increased risk across 18 studies which reported time to death (HR: 1.32, 95% CI: 1.10-1.59). There was very high study heterogeneity (I2 > 94%) and this was not explained by the prespecified subgroup analysis. CONCLUSION: PTSD is associated with increased mortality risk, however further research is required amongst civilians, involving women, and in individuals from underdeveloped countries.

The association between sex hormones and the change in brain-predicted age difference in older women.

OBJECTIVE: The role of circulating sex hormones on structural brain ageing is yet to be established. This study explored whether concentrations of circulating sex hormones in older women are associated with the baseline and longitudinal changes in structural brain ageing, defined by the brain-predicted age difference (brain-PAD). DESIGN: Prospective cohort study using data from NEURO and Sex Hormones in Older Women; substudies of the ASPirin in Reducing Events in the Elderly clinical trial. PATIENTS: Community-dwelling older women (aged 70+ years). MEASUREMENTS: Oestrone, testosterone, dehydroepiandrosterone (DHEA), and sex-hormone binding globulin (SHBG) were quantified from plasma samples collected at baseline. T1-weighted magnetic resonance imaging was performed at baseline, 1 and 3 years. Brain age was derived from whole brain volume using a validated algorithm. RESULTS: The sample comprised of 207 women not taking medications known to influence sex hormone concentrations. A statistically higher baseline brain-PAD (older brain age relative to chronological age) was seen for women in the highest DHEA tertile compared with the lowest in the unadjusted analysis (p = .04). This was not significant when adjusted for chronological age, and potential confounding health and behavioural factors. Oestrone, testosterone and SHBG were not associated with brain-PAD cross-sectionally, nor were any of the examined sex hormones or SHBG associated with brain-PAD longitudinally. CONCLUSION: No strong evidence of an association between circulating sex hormones and brain-PAD. Given there is prior evidence to suggests sex hormones may be important for brain ageing, further studies of circulating sex hormones and brain health in postmenopausal women are warranted.

Factors Influencing Change in Brain-Predicted Age Difference in a Cohort of Healthy Older Individuals.

Background: There is considerable variability in the rate at which we age biologically, and the brain is particularly susceptible to the effects of aging. Objective: We examined the test-retest reliability of brain age at one- and three-year intervals and identified characteristics that predict the longitudinal change in brain-predicted age difference (brain-PAD, defined by deviations of brain age from chronological age). Methods: T1-weighted magnetic resonance images were acquired at three timepoints from 497 community-dwelling adults (73.8±3.5 years at baseline, 48% were female). Brain age was estimated from whole brain volume, using a publicly available algorithm trained on an independent dataset. Linear mixed models were used, adjusting for sex, age, and age2. Results: Excellent retest reliability of brain age was observed over one and three years. We identified a significant sex difference in brain-PAD, where a faster rate of brain aging (worsening in brain age relative to chronological age) was observed in men, and this finding replicated in secondary analyses. The effect size, however, was relatively weak, equivalent to 0.16 years difference per year. A higher score in physical health related quality of life and verbal fluency were associated with a faster rate of brain aging, while depression was linked to a slower rate of brain aging, but these findings were not robust. Conclusion: Our study provides consistent evidence that older men have slightly faster brain atrophy than women. Given the sparsity of longitudinal research on brain age in older populations, future prospective studies are needed to confirm our findings.

Brain-predicted age difference is associated with cognitive processing in later-life.

Brain age is a neuroimaging-based biomarker of aging. This study examined whether the difference between brain age and chronological age (brain-PAD) is associated with cognitive function at baseline and longitudinally. Participants were relatively healthy, predominantly white community-dwelling older adults (n = 531, aged ≥70 years), with high educational attainment (61% ≥12 years) and socioeconomic status (59% ≥75th percentile). Brain age was estimated from T1-weighted magnetic resonance images using an algorithm by Cole et al., 2018. After controlling for age, gender, education, depression and body mass index, brain-PAD was negatively associated with psychomotor speed (Symbol Digit Modalities Test) at baseline (Bonferroni p < 0.006), but was not associated with baseline verbal fluency (Controlled Oral Word Association Test), delayed recall (Hopkins Learning Test Revised), or general cognitive status (Mini-Mental State Examination). Baseline brain-PAD was not associated with 3-year change in cognition (Bonferroni p > 0.006). These findings indicate that even in relatively healthy older people, accelerated brain aging is associated with worse psychomotor speed, but future longitudinal research into changes in brain-PAD is needed.

Health-related heterogeneity in brain aging and associations with longitudinal change in cognitive function.

Introduction: Neuroimaging-based 'brain age' can identify individuals with 'advanced' or 'resilient' brain aging. Brain-predicted age difference (brain-PAD) is predictive of cognitive and physical health outcomes. However, it is unknown how individual health and lifestyle factors may modify the relationship between brain-PAD and future cognitive or functional performance. We aimed to identify health-related subgroups of older individuals with resilient or advanced brain-PAD, and determine if membership in these subgroups is differentially associated with changes in cognition and frailty over three to five years. Methods: Brain-PAD was predicted from T1-weighted images acquired from 326 community-dwelling older adults (73.8 ± 3.6 years, 42.3% female), recruited from the larger ASPREE (ASPirin in Reducing Events in the Elderly) trial. Participants were grouped as having resilient (n=159) or advanced (n=167) brain-PAD, and latent class analysis (LCA) was performed using a set of cognitive, lifestyle, and health measures. We examined associations of class membership with longitudinal change in cognitive function and frailty deficit accumulation index (FI) using linear mixed models adjusted for age, sex and education. Results: Subgroups of resilient and advanced brain aging were comparable in all characteristics before LCA. Two typically similar latent classes were identified for both subgroups of brain agers: class 1 were characterized by low prevalence of obesity and better physical health and class 2 by poor cardiometabolic, physical and cognitive health. Among resilient brain agers, class 1 was associated with a decrease in cognition, and class 2 with an increase over 5 years, though was a small effect that was equivalent to a 0.04 standard deviation difference per year. No significant class distinctions were evident with FI. For advanced brain agers, there was no evidence of an association between class membership and changes in cognition or FI. Conclusion: These results demonstrate that the relationship between brain age and cognitive trajectories may be influenced by other health-related factors. In particular, people with age-resilient brains had different trajectories of cognitive change depending on their cognitive and physical health status at baseline. Future predictive models of aging outcomes will likely be aided by considering the mediating or synergistic influence of multiple lifestyle and health indices alongside brain age.

Factors associated with brain ageing - a systematic review.

BACKGROUND: Brain age is a biomarker that predicts chronological age using neuroimaging features. Deviations of this predicted age from chronological age is considered a sign of age-related brain changes, or commonly referred to as brain ageing. The aim of this systematic review is to identify and synthesize the evidence for an association between lifestyle, health factors and diseases in adult populations, with brain ageing. METHODS: This systematic review was undertaken in accordance with the PRISMA guidelines. A systematic search of Embase and Medline was conducted to identify relevant articles using search terms relating to the prediction of age from neuroimaging data or brain ageing. The tables of two recent review papers on brain ageing were also examined to identify additional articles. Studies were limited to adult humans (aged 18 years and above), from clinical or general populations. Exposures and study design of all types were also considered eligible. RESULTS: A systematic search identified 52 studies, which examined brain ageing in clinical and community dwelling adults (mean age between 21 to 78 years, ~ 37% were female). Most research came from studies of individuals diagnosed with schizophrenia or Alzheimer's disease, or healthy populations that were assessed cognitively. From these studies, psychiatric and neurologic diseases were most commonly associated with accelerated brain ageing, though not all studies drew the same conclusions. Evidence for all other exposures is nascent, and relatively inconsistent. Heterogenous methodologies, or methods of outcome ascertainment, were partly accountable. CONCLUSION: This systematic review summarised the current evidence for an association between genetic, lifestyle, health, or diseases and brain ageing. Overall there is good evidence to suggest schizophrenia and Alzheimer's disease are associated with accelerated brain ageing. Evidence for all other exposures was mixed or limited. This was mostly due to a lack of independent replication, and inconsistency across studies that were primarily cross sectional in nature. Future research efforts should focus on replicating current findings, using prospective datasets. TRIAL REGISTRATION: A copy of the review protocol can be accessed through PROSPERO, registration number CRD42020142817 .

Effect of Statin Therapy on Cognitive Decline and Incident Dementia in Older Adults.

BACKGROUND: The neurocognitive effect of statins in older adults remain uncertain. OBJECTIVES: The aim of this study was to investigate the associations of statin use with cognitive decline and incident dementia among older adults. METHODS: This analysis included 18,846 participants ≥65 years of age in a randomized trial of aspirin, who had no prior cardiovascular events, major physical disability, or dementia initially and were followed for 4.7 years. Outcome measures included incident dementia and its subclassifications (probable Alzheimer's disease, mixed presentations); mild cognitive impairment (MCI) and its subclassifications (MCI consistent with Alzheimer's disease, other MCI); and changes in domain-specific cognition, including global cognition, memory, language and executive function, psychomotor speed, and the composite of these domains. Associations of baseline statin use versus nonuse with dementia and MCI outcomes were examined using Cox proportional hazards models and with cognitive change using linear mixed-effects models, adjusting for potential confounders. The impact of statin lipophilicity on these associations was further examined, and effect modifiers were identified. RESULTS: Statin use versus nonuse was not associated with dementia, MCI, or their subclassifications or with changes in cognitive function scores over time (p > 0.05 for all). No differences were found in any outcomes between hydrophilic and lipophilic statin users. Baseline neurocognitive ability was an effect modifier for the associations of statins with dementia (p for interaction < 0.001) and memory change (p for interaction = 0.02). CONCLUSIONS: In adults ≥65 years of age, statin therapy was not associated with incident dementia, MCI, or declines in individual cognition domains. These findings await confirmation from ongoing randomized trials.

A Systematic Review and Meta-analysis of Environmental, Lifestyle, and Health Factors Associated With DNA Methylation Age.

DNA methylation (DNAm) algorithms of biological age provide a robust estimate of an individual's chronological age and can predict their risk of age-related disease and mortality. This study reviewed the evidence that environmental, lifestyle and health factors are associated with the Horvath and Hannum epigenetic clocks. A systematic search identified 61 studies. Chronological age was correlated with DNAm age in blood (median .83, range .13-.99). In a meta-analysis body mass index (BMI) was associated with increased DNAm age (Hannum ß: 0.07, 95% CI 0.04 to 0.10; Horvath ß: 0.06, 95% CI 0.02 to 0.10), but there was no association with smoking (Hannum ß: 0.12, 95% CI -0.50 to 0.73; Horvath ß:0.18, 95% CI -0.10 to 0.46). DNAm age was positively associated with frailty (three studies, n = 3,093), and education was negatively associated with the Hannum estimate of DNAm age specifically (four studies, n = 13,955). For most other exposures, findings were too inconsistent to draw conclusions. In conclusion, BMI was positively associated with biological aging measured using DNAm, with some evidence that frailty also increased aging. More research is needed to provide conclusive evidence regarding other exposures. This field of research has the potential to provide further insights into how to promote slower biological aging and ultimately prolong healthy life.

The epigenetic clock as a predictor of disease and mortality risk: a systematic review and meta-analysis.

BACKGROUND: Ageing is one of the principal risk factors for many chronic diseases. However, there is considerable between-person variation in the rate of ageing and individual differences in their susceptibility to disease and death. Epigenetic mechanisms may play a role in human ageing, and DNA methylation age biomarkers may be good predictors of age-related diseases and mortality risk. The aims of this systematic review were to identify and synthesise the evidence for an association between peripherally measured DNA methylation age and longevity, age-related disease, and mortality risk. METHODS: A systematic search was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Using relevant search terms, MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and PsychINFO databases were searched to identify articles meeting the inclusion criteria. Studies were assessed for bias using Joanna Briggs Institute critical appraisal checklists. Data was extracted from studies measuring age acceleration as a predictor of age-related diseases, mortality or longevity, and the findings for similar outcomes compared. Using Review Manager 5.3 software, two meta-analyses (one per epigenetic clock) were conducted on studies measuring all-cause mortality. RESULTS: Twenty-three relevant articles were identified, including a total of 41,607 participants. Four studies focused on ageing and longevity, 11 on age-related disease (cancer, cardiovascular disease, and dementia), and 11 on mortality. There was some, although inconsistent, evidence for an association between increased DNA methylation age and risk of disease. Meta-analyses indicated that each 5-year increase in DNA methylation age was associated an 8 to 15% increased risk of mortality. CONCLUSION: Due to the small number of studies and heterogeneity in study design and outcomes, the association between DNA methylation age and age-related disease and longevity is inconclusive. Increased epigenetic age was associated with mortality risk, but positive publication bias needs to be considered. Further research is needed to determine the extent to which DNA methylation age can be used as a clinical biomarker.

Brain-derived neurotrophic factor DNA methylation mediates the association between neighborhood disadvantage and adolescent brain structure.

Prior research indicates that socioeconomic disadvantage is associated with prefrontal cortical (PFC) development in childhood and adolescence, however the mechanisms of this link are unclear. This study investigated whether DNA methylation of the brain-derived neurotrophic factor (BDNF, which plays a key role in synaptic plasticity), mediated the association between neighborhood disadvantage and thickness of the PFC in adolescents. Neighborhood disadvantage was measured in 33 adolescents aged 12-13 years using the Socio-Economic Indexes for Areas. Buccal swabs, collected during mid-adolescence (aged 16-18 years), enabled BDNF DNA methylation of the widely studied exon IV promoter region to be measured. Cortical thickness was assessed during late-adolescence (aged 18-20 years) via T1-weighted magnetic resonance imaging (MRI). A significant negative association between disadvantage and BDNF DNA methylation at a specific site of the exon IV promoter was identified. Lower levels of methylation were also significantly associated with greater thickness of the lateral orbitofrontal cortex (lOFC), and right medial OFC. Lower levels of DNA methylation at this site also mediated associations between higher disadvantage and thinner bilateral lOFC thickness. These novel findings give insight into a potential biological mechanism that could further our understanding as to why brain development is affected by varying environmental exposures.

Association between DNA methylation of the KITLG gene and cortisol levels under stress: a replication study.

A recent study reported for the first time, that DNA methylation of the KITLG gene mediates the association between childhood trauma and cortisol stress reactivity. Our study aimed to provide the first independent replication of these findings. ESPRIT is a prospective study of community-dwelling participants (age ≥ 65), randomly selected from the electoral rolls of the Montpellier district, in France. Clinical depression was assessed using the Mini-International Neuropsychiatric Interview (MINI, French version 5.00), and the Centre for Epidemiological Studies Depression Scale (CES-D). Experiences of childhood adversity were ascertained via a 25-item questionnaire. Morning, evening, and diurnal salivary cortisol was measured under basal and stress conditions and determined using direct radioimmunoassay analysis. DNA methylation of the KITLG gene was quantified in whole blood using the SEQUENOM MassARRAY EpiTYPER platform. A significant negative association was observed between KITLG DNA methylation and both morning cortisol (ß = -1.846 ± 0.666, p = .007) and diurnal cortisol (area under curve [AUC]) (ß = -19.429 ± 8.868, p = .031) under a stress condition. However, only the former association was significant after correcting for multiple testing. Further, this association remained after adjusting for age, sex, and depression status. No significant association was observed between childhood trauma and KITLG DNA methylation in this older population. This study provides support for an association between KITLG methylation and stress cortisol levels, suggesting that DNA methylation of this gene may play a role in the longer term regulation of the stress system. Lay summary The significant negative association between KITLG DNA methylation and morning cortisol, measured under a stressful condition, suggests that individuals with higher KITLG methylation will secrete lower levels of cortisol whilst under stress.

Phenotypic Heterogeneity in Dementia: A Challenge for Epidemiology and Biomarker Studies.

Dementia can result from a number of distinct diseases with differing etiology and pathophysiology. Even within the same disease, there is considerable phenotypic heterogeneity with varying symptoms and disease trajectories. Dementia diagnosis is thus very complex, time-consuming, and expensive and can only be made definitively post-mortem with histopathological confirmation. These inherent difficulties combined with the overlap of some symptoms and even neuropathological features, present a challenging problem for research in the field. This has likely hampered progress in epidemiological studies of risk factors and preventative interventions, as well as genetic and biomarker research. Resource limitations in large epidemiologically studies mean that limited diagnostic criteria are often used, which can result in phenotypically heterogeneous disease states being grouped together, potentially resulting in misclassification bias. When biomarkers are identified for etiologically heterogeneous diseases, they will have low specificity for any utility in clinical practice, even if their sensitivity is high. We highlight several challenges in in the field which must be addressed for the success of future genetic and biomarker studies, and may be key to the development of the most effective treatments. As a step toward achieving this goal, defining the dementia as a biological construct based on the presence of specific pathological features, rather than clinical symptoms, will enable more precise predictive models. It has the potential to lead to the discovery of novel genetic variants, as well as the identification of individuals at heightened risk of the disease, even prior to the appearance of clinical symptoms.