Cambridge City Over-75s Cohort Study Research Articles

Frailty and neuropathology in relation to dementia status: the Cambridge City over-75s Cohort study

To examine the relative contributions of frailty and neuropathology to dementia expression in a population-based cohort study. Cross-sectional analysis of observational data. Population-representative clinicopathological cohort study. Adults aged 75+ recruited from general practice registries in Cambridge, UK, in 1985. A 39-item frailty index and 15-item neuropathological index were used to operationalize frailty and neuropathology, respectively. Dementia status was ascertained by clinical consensus at time of death. Relationships were evaluated using logistic regression models in participants with autopsy records (n = 183). Model fit was assessed using change in deviance. Population attributable fraction for frailty was evaluated in relation to dementia incidence in a representative sample of the survey participants (n = 542). Participants with autopsy were 92.3 ± 4.6 years at time of death, and mostly women (70%). Average frailty index value at last survey before death was 0.34 ± 0.16. People with dementia (63% of the sample) were frailer, had lower MMSE scores, and a higher burden of neuropathology. Frailty and neuropathological burden were significantly and independently associated with dementia status, without interaction; frailty explained an additional 3% of the variance in the model. Assuming a causal relationship and based on population-attributable fraction analyses, preventing severe frailty (Frailty Index ≥ 0.40) could have avoided 14.2% of dementia cases in this population-based cohort. In the very old, frailty contributes to the risk for dementia beyond its relationship with the burden of traditional dementia neuropathologies. Reducing frailty could have important implications for controlling the burden of dementia. Future research on frailty interventions should include dementia risk as a key outcome, public health interventions and policy decisions should consider frailty as a key risk factor for dementia, and biomedical research should focus on elucidating shared mechanisms of frailty and dementia development.

Is loneliness associated with increased health and social care utilisation in the oldest old? Findings from a population-based longitudinal study

ObjectivesThe present study aimed to examine the impact of loneliness on health and social care service use in the oldest old over a 7-year follow-up.DesignProspective study.SettingUK population-based cohort.Participants713 people aged...

Lack of associations between modifiable risk factors and dementia in the very old: findings from the Cambridge City over-75s cohort study

ABSTRACTObjectives: To investigate the association between modifiable risk and protective factors and severe cognitive impairment and dementia in the very old. Additionally, the present study tests the predictive validity of the ‘LIfestyle for BRAin health’ (LIBRA) score, an index developed to assess an individual's dementia prevention potential.Method: Two hundred seventy-eight individuals aged 85 years or older from the Cambridge City over-75s cohort study were followed-up until death. Included risk and protective factors were: diabetes, heart disease, hypertension, depression, smoking, low-to-moderate alcohol use, high cognitive activity, and physical inactivity. Incident severe cognitive impairment was based on the Mini-Mental State Examination (score: 0-17) and incident dementia was based on either post-mortem consensus clinical diagnostic assessments or death certificate data. Logistic regressions were used to test whether individual risk and protective factors and the LIBRA score were associated with severe cognitive impairment or dementia after 18 years follow-up.Results: None of the risk and protective factors or the LIBRA score was significantly associated with increased risk of severe cognitive impairment or dementia. Sensitivity analyses using a larger sample, longer follow-up period, and stricter cut-offs for prevalent cognitive impairment showed similar results.Conclusion: Associations between well-known midlife risk and protective factors and risk for severe cognitive impairment or dementia might not persist into very old age, in line with suggestions that targeting these factors through lifestyle interventions should start earlier in life.

Successful ageing trajectories at the end of life: a longitudinal population-based cohort study

BackgroundDespite the acknowledgment that successful ageing is a heterogeneous life-course process, present models of successful ageing are unable to accommodate decline at the end of life because of methodological and conceptual limitations. The present study aimed to address these limitations, identifying different trajectories of successful ageing at the end of life. MethodsThe Successful Ageing Index (SAI), which is a scale consisting of components identified by systematic reviews of layperson perspectives and operational definitions of successful ageing, was collected in a longitudinal population-based cohort study of individuals aged 75 years and older—the Cambridge City over-75s Cohort Study (CC75C). SAI scores were examined longitudinally with growth mixture modelling (GMM) to identify classes of participants with similar trajectories; in this model decedents’ (n=1015) last completed interview and up to four previous data collection waves before death were used. Classes identified by GMM were compared by means of logistic regression models. FindingsA three-class model was identified: a high-functioning, no decline (HN) class; a high-functioning, gradual decline (HG) class; and a low-functioning, steep decline (LS) class. Individuals in the HN class were significantly younger at death (88·3 years [SD 4·9]) than were those in the HG (89·9 [5·0], p<0·0001) and LS classes (90·5 [5·1], p<0·0001); were significantly younger at their last interview (82·9 years [3·6] vs 85·0 [4·2] in the HG class [p<0·0001] and 86·3 [4·7] in the LS class [p<0·0001]); consisted of more men (52% men vs 31% in the HG class [p<0·0001] and 22% in the LS class [p<0·0001]); and were more likely to be married (51% vs 24% in the HG class [p<0·0001] and 19% in the LS class [p=0·0001]). InterpretationSuccessful ageing trajectories at the end of life are heterogeneous; individuals can experience many different trajectories towards death. Methods used in this study provide novel insights into successful ageing at the end of life. The present study provides the methodological framework for future research, with important implications for policy and practice, as well as insights into the demographic characteristics of end of life trajectories. FundingNone.

Joint Models for Discrete Longitudinal Outcomes in Aging Research

SummaryGiven the aging population in the UK, statistical modelling of cognitive function in the older population is of interest. Joint models are formulated for survival and cognitive function in the older population. Because tests of cognitive function often result in discrete outcomes, binomial and beta–binomial mixed effects regression models are applied to analyse longitudinal measurements. Dropout due to death is accounted for by parametric survival models, where the choice of a Gompertz baseline hazard and the specification of the random-effects structure are of specific interest. The measurement model and the survival model are combined in a shared parameter joint model. Estimation is by marginal likelihood. The methods are used to analyse data from the Cambridge City over-75s cohort study and the English Longitudinal Study of Ageing.

Longitudinal mixed-effects models for latent cognitive function

A mixed-effects regression model with a bent-cable change-point predictor is formulated to describe potential decline of cognitive function over time in the older population. For the individual trajectories, cognitive function is considered to be a latent variable measured through an item response theory model given longitudinal test data. Individual-specific parameters are defined for both cognitive function and the rate of change over time, using the change-point predictor for non-linear trends. Bayesian inference is used, where the Deviance Information Criterion and the L-criterion are investigated for model comparison. Special attention is given to the identifiability of the item response parameters. Item response theory makes it possible to use dichotomous and polytomous test items, and to take into account missing data and survey-design change during follow-up. This will be illustrated in an application where data stem from the Cambridge City over-75s Cohort Study.

Epidemiology of back pain in older adults: prevalence and risk factors for back pain onset

To determine the prevalence of disabling and non-disabling back pain across age in older adults, and identify risk factors for back pain onset in this age group. Participants aged ≥ 75 years answered interviewer-administered questions on back pain as part of a prospective cohort study [Cambridge City over-75s Cohort Study (CC75C)]. Descriptive analyses of data from two surveys, 1988-89 and 1992-93, estimated prevalence and new onset of back pain. Relative risks (RRs) and 95% CIs were estimated using Poisson regression, adjusted for age and gender. Prevalence of disabling and non-disabling back pain was 6 and 23%, respectively. While prevalence of non-disabling back pain did not vary significantly across age (χ²trend : 0.90; P = 0.34), the prevalence of disabling back pain increased with age (χ²trend : 4.02; P = 0.04). New-onset disabling and non-disabling back pain at follow-up was 15 and 5%, respectively. Risk factors found to predict back pain onset at follow-up were: poor self-rated health (RR 3.8; 95% CI 1.8, 8.0); depressive symptoms (RR 2.2; 95% CI 1.3, 3.7); use of health or social services (RR 1.7; 95% CI 1.1, 2.7); and previous back pain (RR 2.1; 95% CI 1.2-3.5). From these, poor self-rated health, previous back pain and depressive symptoms were found to be independent predictors of pain onset. Markers of social networks were not associated with the reporting of back pain onset. Conclusion. The risk of disabling back pain rises in older age. Older adults with poor self-rated health, depressive symptoms, increased use of health and social services and a previous episode of back pain are at greater risk of reporting future back pain onset.

Falls in advanced old age: recalled falls and prospective follow-up of over-90-year-olds in the Cambridge City over-75s Cohort study.

BackgroundThe "oldest old" are now the fastest growing section of most western populations, yet there are scarcely any data concerning even the common problem of falls amongst the very old. Prospective data collection is encouraged as the most reliable method for researching older people's falls, though in clinical practice guidelines advise taking a history of any recalled falls. This study set out to inform service planning by describing the epidemiology of falls in advanced old age using both retrospectively and prospectively collected falls data.MethodsDesign: Re-survey of over-90-year-olds in a longitudinal cohort study – cross-sectional interview and intensive 12-month follow-up.Participants and setting: 90 women and 20 men participating in a population-based cohort (aged 91–105 years, in care-homes and community-dwelling) recruited from representative general practices in Cambridge, UKMeasurements: Prospective falls data were collected using fall calendars and telephone follow-up for one year after cross-sectional survey including fall history.Results58% were reported to have fallen at least once in the previous year and 60% in the 1-year follow-up. The proportion reported to have fallen more than once was lower using retrospective recall of the past year than prospective reports gathered the following year (34% versus 45%), as were fall rates (1.6 and 2.8 falls/person-year respectively). Repeated falls in the past year were more highly predictive of falls during the following year – IRR 4.7, 95% CI 2.6–8.7 – than just one – IRR 3.6, 95% CI 2.0–6.3, using negative binomial regression. Only 1/5 reportedly did not fall during either the year before or after interview.ConclusionFall rates in this representative sample of over-90-year-olds are even higher than previous reports from octogenarians. Recalled falls last year, particularly repeated falls, strongly predicted falls during follow-up. Similar proportions of people who fell were reported by retrospective and prospective methods covering two consecutive years. Recall methods may underestimate numbers of repeated falls and the extent of recurrent falling. Professionals caring for people of advanced age can easily ask routinely whether someone has fallen at all, or more than once, in the past year to identify those at high risk of subsequent falls.