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Understanding the causes of Alzheimer’s disease and related dementias remains a challenge. Observational studies investigating dementia risk factors are limited by the pervasive issues of confounding, reverse causation and selection biases. Conducting randomised controlled trials for dementia prevention is often impractical due to the long prodromal phase and the inability to randomise many potential risk factors. In this essay, we introduce Mendelian randomisation as an alternative approach to examine factors that may prevent or delay Alzheimer’s disease. Mendelian randomisation is a causal inference method that has successfully identified risk factors and treatments in various other fields. However, applying this method to dementia risk factors has yielded unexpected findings. Here, we consider five potential explanations and provide recommendations to enhance causal inference from Mendelian randomisation studies on dementia. By employing these strategies, we can better understand factors affecting dementia risk.

ObjectivesTo examine the associations of COVID-19-related changes in work with perceptions of psychosocial work environment and employee health.MethodsIn a cohort of 24 299 Finnish public sector employees, psychosocial work environment and employee well-being were assessed twice before (2016 and 2018=reference period) and once during (2020) the COVID-19 pandemic. Those who reported a change (=‘Exposed’) in work due to the pandemic (working from home, new tasks or team reorganisation) were compared with those who did not report such change (=‘Non-exposed’).ResultsAfter adjusting for sex, age, socioeconomic status and lifestyle risk score, working from home (44%) was associated with greater increase in worktime control (standardised mean difference (SMD)Exposed=0.078, 95% CI 0.066 to 0.090; SMDNon-exposed=0.025, 95% CI 0.014 to 0.036), procedural justice (SMDExposed=0.101, 95% CI 0.084 to 0.118; SMDNon-exposed=0.053, 95% CI 0.038 to 0.068), workplace social capital (SMDExposed=0.094, 95% CI 0.077 to 0.110; SMDNon-exposed=0.034, 95% CI 0.019 to 0.048), less decline in self-rated health (SMDExposed=−0.038, 95% CI −0.054 to –0.022; SMDNon-exposed=−0.081, 95% CI −0.095 to –0.067), perceived work ability (SMDExposed=−0.091, 95% CI −0.108 to –0.074; SMDNon-exposed=−0.151, 95% CI −0.167 to –0.136) and less increase in psychological distress (risk ratio (RR)Exposed=1.06, 95% CI 1.02 to 1.09; RRNon-exposed=1.16, 95% CI 1.13 to 1.20). New tasks (6%) were associated with greater increase in psychological distress (RRExposed=1.28, 95% CI 1.19 to 1.39; RRNon-exposed=1.10, 95% CI 1.07 to 1.12) and team reorganisation (5%) with slightly steeper decline in perceived work ability (SMDExposed=−0.151 95% CI −0.203 to –0.098; SMDNon-exposed=−0.124, 95% CI −0.136 to –0.112).ConclusionEmployees who worked from home during the pandemic had more favourable psychosocial work environment and health, whereas those who were exposed to work task changes and team reorganisations experienced more adverse changes.

Study objectivesTo examine the association between sleep duration and sleep difficulties with different types and causes of workplace and commuting injuries.MethodsThe data were derived from the Finnish Public Sector study including 89.543 participants (178.309 person-observations). Participants reported their sleep duration and sleep difficulties between 2000 and 2012. These were linked to occupational injury records from the national register maintained by the Federation of Accident Insurance Institutions. Risk of injuries was followed up 1 year after each study wave. Logistic regression analysis with generalised estimating equations (GEEs) was used to examine the association between sleep duration/difficulties and risk of injuries, and multinomial logistic regression with GEE was used to examine the association with injury types and causes.ResultsBoth sleep duration and difficulties were associated with injuries. Employees with short sleep (≤6.5 hours) had 1.07-fold odds of workplace injuries (95% CI 1.00 to 1.14) and 1.14 times higher odds of commuting injuries (95% CI 1.04 to 1.26) compared with employees with normal sleep duration. For employees with disturbed sleep, the corresponding ORs were 1.09-fold (95% CI 1.02 to 1.17) and 1.14-fold (95% CI 1.04 to 1.26) compared with those without sleep difficulties, respectively. The risk of commuting injuries was higher among those who had difficulty in falling asleep (OR 1.29, 95% CI 1.07 to 1.55), woke up too early (OR 1.11, 95% CI 1.00 to 1.23) or had non-restorative sleep (OR 1.18, 95% CI 1.05 to 1.33).ConclusionsShort sleep duration and sleep difficulties are associated with slightly increased risk of workplace and commuting injuries.

ObjectivesStudies concerning the association between shift work and drinking problems showed inconsistent results. We used data from a large occupational cohort to examine the association between shift work and different types of drinking behaviour.MethodsA total of 93 121 non-abstinent workers from the Finnish Public Sector Study were enrolled in the study. Six waves of survey data were collected between 2000 and 2017. Work schedules were categorised as regular day, non-night shift and night shift work, and shift intensities were calculated from registered working hour data. Two indicators of adverse drinking behaviour were measured: at-risk drinking (>7 and >14 drinks per week in women and men, respectively) and high-intensity drinking (measured as pass-out experience). Intraindividual analysis was conducted using fixed-effects regression to examine the association between shift work and drinking behaviours.ResultsCompared with regular day work, night shift work was associated with an increased risk of high-intensity drinking (OR 1.28, 95% CI 1.07 to 1.52) but a lower risk of at-risk drinking (OR 0.85, 95% CI 0.74 to 0.99). Shift workers who worked long shifts had a lower risk of at-risk drinking compared with those who rarely worked long shifts (OR 0.58, 95% CI 0.37 to 0.93).ConclusionsAssociations between shift work and alcohol use vary according to drinking patterns. Workers engaged in high-intensity drinking more often during night shift schedules compared with day work, but did not drink averagely higher volume.

ObjectiveThis study aimed to compare the development of self-rated health, psychological distress and physical functioning between those retired on time and those who continued working beyond the individual retirement age.MethodsThe study population consisted of 2340 public sector employees from the Finnish Retirement and Aging study. Participants were categorised into no extension of employment (retired at the individual retirement date or <3 months past) and extension of employment (≥12 months). Propensity score matching (1:1 ratio) was used to identify comparable group of participants in the no-extension (n=574) and extension (n=574) groups by taking into account preretirement characteristics and their interactions.ResultsThe prevalence of suboptimal self-rated health and psychological distress changed a little among the extension group during the follow-up from 1 year before (T1) to 18 months (T2) and 30 months (T3) after individual pensionable date. Compared with no extension, the risk of having suboptimal self-rated health in the extension group was 0.89 (95% CI 0.68 to 1.17) at T1, 1.16 (95% CI 0.88 to 1.53) at T2 and 0.96 (95% CI 0.68 to 1.37) at T3. For psychological distress, the corresponding risk ratios were 0.93 (0.65 to 1.32), 1.15 (0.78 to 1.69) and 1.04 (0.61 to 1.79). The mean differences in the number of physical functioning difficulties between the extension and no-extension groups were 0.06 (−0.16 to 0.29) at T1, 0.05 (−0.18 to 0.27) at T2 and −0.11 (−0.39 to 0.17) at T3.ConclusionsThis study found no evidence that voluntarily extending the working career beyond retirement age would pose a risk to health and physical functioning among ageing workers.

BackgroundThis study aimed to identify the trajectories of work ability over 16 years preceding the individual pensionable age and to examine the association with retirement timing.MethodsThe study population consisted of 2612 public sector employees from the Finnish Retirement and Aging study and the Finnish Public Sector study. Participants were grouped into ‘no-extension’ (retired at the individual pensionable date or worked no longer than 6 months after that date) and ‘extension’ (worked more than 6 months after individual pensionable age). Trajectories of self-reported work ability score (0–10) in maximum of eight measurement points over 16 years preceding retirement were examined using the group-based latent trajectory analysis. Log-binomial regression was used to analyse the association between trajectory groups and extended employment.ResultsFour stable (‘Stable excellent’, 7%; ‘Stable high’, 62%; ‘Stable medium’, 24%; ‘Low’, 4%) and one decreasing (‘Declining’, 3%) work ability trajectories were identified. After taking into account gender, age, occupational status, marital status and self-rated health, ‘Stable excellent’ trajectory was associated with a higher likelihood of extended employment compared with the ‘Low’ (risk ratio (RR) 2.38, 95% CI 1.21 to 4.68) and to the ‘Declining’ (RR 2.82, 95% CI 1.32 to 6.01) trajectories. There was no difference in retirement timing between ‘Declining’, ‘Low’ and ‘Stable medium’ trajectories.ConclusionWork ability remained relatively stable among majority of the participants over 16 years of follow-up. Stable excellent work ability from mid-life to late career was associated with higher likelihood of extending employment beyond individual pensionable age than those with low or declining work ability.

BackgroundAttrition, the loss of participants as a study progresses, is a considerable challenge in longitudinal studies. This study examined whether two forms of attrition, ‘withdrawal’ (formal discontinued participation) and ‘non-response’ (non-response among participants continuing in the study), have different associations with mortality and whether these associations differed across time in a multi-wave longitudinal study.MethodsParticipants were 10 012 civil servants who participated at the baseline of the Whitehall II cohort study with 11 data waves over an average follow-up of 28 years. We performed competing-risks analyses to estimate sub-distribution HRs and 95% CIs, and likelihood ratio tests to examine whether hazards differed between the two forms of attrition. We then applied linear regression to examine any trend of hazards against time.ResultsAttrition rate at data collections ranged between 13% and 34%. There were 495 deaths recorded from cardiovascular disease and 1367 deaths from other causes. Study participants lost due to attrition had 1.55 (95% CI 1.26 to 1.89) and 1.56 (1.39 to 1.76) times higher hazard of cardiovascular and non-cardiovascular mortality than responders, respectively. Hazards for withdrawal and non-response did not differ for either cardiovascular (p value =0.28) or non-cardiovascular mortality (p value =0.38). There was no linear trend in hazards over the 11 waves (cardiovascular mortality p value =0.11, non-cardiovascular mortality p value =0.61).ConclusionAttrition can be a problem in longitudinal studies resulting in selection bias. Researchers should examine the possibility of selection bias and consider applying statistical approaches that minimise this bias.

BackgroundPersonality traits have been liked to cognitive outcomes such as dementia, but whether these associations are robust to the effects of third variables remains the subject of debate. We examined the role of socioeconomic status, depression (history and depressive symptoms), health behaviours and chronic conditions in the association of the big-5 personality traits with cognitive performance, cognitive impairment and incidence of dementia.MethodsData on 6135 persons (30% women), aged 60–83 years in 2012/13, are drawn from the Whitehall II Study. Participants responded to the 26-item Midlife Development Inventory to assess personality traits (openness, conscientiousness, extraversion, agreeableness and neuroticism), underwent cognitive testing in 2012/13 and 2015/16 and were followed for incidence of dementia (N=231) until 2019.ResultsLogistic regression, adjusted for sociodemographic factors, suggested a cross-sectional association with cognitive impairment for four of the five traits but only neuroticism was associated with incident cognitive impairment. All associations were completely attenuated when the analyses were adjusted for depression. Cox regression (mean follow-up: 6.18 years) adjusted for sociodemographic variables showed higher conscientiousness (HR per SD increment=0.72; 95% CI 0.65 to 0.81) and extraversion (HR=0.85; 95% CI 0.75 to 0.97) to be associated with lower dementia risk; higher neuroticism (HR=1.32; 95% CI 1.17 to 1.49) was associated with increased risk. Further adjustment for depression led to only conscientiousness retaining an association with dementia (HR=0.81; 95% CI 0.69 to 0.96), which was robust to adjustment for all covariates (HR=0.84; 95% CI 0.71 to 0.91; P=0.001).ConclusionOur results show that only conscientiousness has an association with incidence of dementia that is not attributable to socioeconomic status or depression. The association of neuroticism with dementia was explained by depression.

ObjectivesPrevious studies have produced conflicting findings on the health consequences of retirement. We aimed at identifying trajectories of self-rated health over retirement transition using repeated measurements and examined which preretirement factors predicted membership to each trajectory.MethodsThe study population consisted of Finnish public sector employees from two independent cohorts (Finnish Public Sector Study (FPS), n=5776 with a 4-year follow-up interval; and Finnish Retirement and Aging Study (FIREA), n=2796 with a 1-year follow-up interval). Both cohorts included assessment of self-rated health one to three times before and one to three times after retirement (average number of measurement points: 3.7 in FPS and 3.5 in FIREA). We used latent trajectory analysis to identify trajectories of self-rated health.ResultsIn both cohorts four similar trajectories were identified: ‘Sustained good health’ (47% in FPS and 74% in FIREA), ‘From good to suboptimal health’ (19% and 6%), ‘From suboptimal to good health’ (14% and 8%) and ‘Sustained suboptimal health’ (20% and 12%). There were more women and persons in high occupational status in the ‘From suboptimal to good health’ trajectory group when compared with ‘Sustained suboptimal health’ trajectory group in FPS. Those in the trajectory ‘From good to suboptimal health’ had lower occupational status and higher job strain in comparison with those in the ‘Sustained good health’ trajectory in both cohorts.ConclusionsA large majority of public sector employees maintain their perceived health status during retirement transition. Adverse trajectory in self-rated health relate to low occupational status and work-related stressors.

ObjectivesSeveral recent large-scale studies have indicated a prospective association between job strain and coronary heart disease, stroke and diabetes. Job strain is also associated with poorer mental health, a risk factor for cardiometabolic disease. This study investigates the prospective relationships between change in job strain, poor mental health and cardiometabolic disease, and whether poor mental health is a potential mediator of the relationship between job strain and cardiometabolic disease.MethodsWe used data from five cohort studies from Australia, Finland, Sweden and UK, including 47 757 men and women. Data on job strain across two measurements 1–5 years apart (time 1 (T1)–time 2 (T2)) were used to define increase or decrease in job strain. Poor mental health (symptoms in the top 25% of the distribution of the scales) at T2 was considered a potential mediator in relation to incident cardiometabolic disease, including cardiovascular disease and diabetes, following T2 for a mean of 5–18 years.ResultsAn increase in job strain was associated with poor mental health (HR 1.56, 95% CI 1.38 to 1.76), and a decrease in job strain was associated with lower risk in women (HR 0.70, 95% CI 0.60–0.84). However, no clear association was observed between poor mental health and incident cardiometabolic disease (HR 1.08, 95% CI 0.96–1.23), nor between increase (HR 1.01, 95% CI 0.90–1.14) and decrease (HR 1.08, 95% CI 0.96–1.22) in job strain and cardiometabolic disease.ConclusionsThe results did not support that change in job strain is a risk factor for cardiometabolic disease and yielded no support for poor mental health as a mediator.

BackgroundAlthough long working hours have been shown to be associated with the onset of cardiometabolic diseases, the clinical risk factor profile associated with long working hours remains unclear. We compared the clinical risk profile between people who worked long hours and those who reported being never exposed to long hours.MethodsA cross-sectional study in 22 health screening centres in France was based on a random population-based sample of 75 709 participants aged 18–69 at study inception in 2012–2016 (the CONSTANCES study). The data included survey responses on working hours (never, former or current exposure to long working hours), covariates and standardised biomedical examinations including anthropometry, lung function, blood pressure and standard blood-based biomarkers.ResultsAmong men, long working hours were associated with higher anthropometric markers (Body Mass Index, waist circumference and waist:hip ratio), adverse lipid levels, higher glucose, creatinine, white blood cells and higher alanine transaminase (adjusted mean differences in the standardised scale between the exposed and unexposed 0.02–0.12). The largest differences were found for Body Mass Index and waist circumference. A dose–response pattern with increasing years of working long hours was found for anthropometric markers, total cholesterol, glucose and gamma-glutamyltransferase. Among women, long working hours were associated with Body Mass Index and white blood cells.ConclusionIn this study, men who worked long hours had slightly worse cardiometabolic and inflammatory profile than those who did not work long hours, especially with regard to anthropometric markers. In women, the corresponding associations were weak or absent.

BackgroundCurrent dementia risk scores have had limited success in consistently identifying at-risk individuals across different ages and geographical locations.ObjectiveWe aimed to develop and validate a novel dementia risk score for a midlife UK population, using two cohorts: the UK Biobank, and UK Whitehall II study.MethodsWe divided the UK Biobank cohort into a training (n=176 611, 80%) and test sample (n=44 151, 20%) and used the Whitehall II cohort (n=2934) for external validation. We used the Cox LASSO regression to select the strongest predictors of incident dementia from 28 candidate predictors and then developed the risk score using competing risk regression.FindingsOur risk score, termed the UK Biobank Dementia Risk Score (UKBDRS), consisted of age, education, parental history of dementia, material deprivation, a history of diabetes, stroke, depression, hypertension, high cholesterol, household occupancy, and sex. The score had a strong discrimination accuracy in the UK Biobank test sample (area under the curve (AUC) 0.8, 95% CI 0.78 to 0.82) and in the Whitehall cohort (AUC 0.77, 95% CI 0.72 to 0.81). The UKBDRS also significantly outperformed three other widely used dementia risk scores originally developed in cohorts in Australia (the Australian National University Alzheimer’s Disease Risk Index), Finland (the Cardiovascular Risk Factors, Ageing, and Dementia score), and the UK (Dementia Risk Score).Clinical implicationsOur risk score represents an easy-to-use tool to identify individuals at risk for dementia in the UK. Further research is required to determine the validity of this score in other populations.

ObjectivesTo examine the association between cognitively stimulating work and subsequent risk of dementia and to identify protein pathways for this association.DesignMulticohort study with three sets of analyses.SettingUnited Kingdom, Europe, and the United States.ParticipantsThree associations were examined: cognitive stimulation and dementia risk in 107 896 participants from seven population based prospective cohort studies from the IPD-Work consortium (individual participant data meta-analysis in working populations); cognitive stimulation and proteins in a random sample of 2261 participants from one cohort study; and proteins and dementia risk in 13 656 participants from two cohort studies.Main outcome measuresCognitive stimulation was measured at baseline using standard questionnaire instruments on active versus passive jobs and at baseline and over time using a job exposure matrix indicator. 4953 proteins in plasma samples were scanned. Follow-up of incident dementia varied between 13.7 to 30.1 years depending on the cohort. People with dementia were identified through linked electronic health records and repeated clinical examinations.ResultsDuring 1.8 million person years at risk, 1143 people with dementia were recorded. The risk of dementia was found to be lower for participants with high compared with low cognitive stimulation at work (crude incidence of dementia per 10 000 person years 4.8 in the high stimulation group and 7.3 in the low stimulation group, age and sex adjusted hazard ratio 0.77, 95% confidence interval 0.65 to 0.92, heterogeneity in cohort specific estimates I2=0%, P=0.99). This association was robust to additional adjustment for education, risk factors for dementia in adulthood (smoking, heavy alcohol consumption, physical inactivity, job strain, obesity, hypertension, and prevalent diabetes at baseline), and cardiometabolic diseases (diabetes, coronary heart disease, stroke) before dementia diagnosis (fully adjusted hazard ratio 0.82, 95% confidence interval 0.68 to 0.98). The risk of dementia was also observed during the first 10 years of follow-up (hazard ratio 0.60, 95% confidence interval 0.37 to 0.95) and from year 10 onwards (0.79, 0.66 to 0.95) and replicated using a repeated job exposure matrix indicator of cognitive stimulation (hazard ratio per 1 standard deviation increase 0.77, 95% confidence interval 0.69 to 0.86). In analysis controlling for multiple testing, higher cognitive stimulation at work was associated with lower levels of proteins that inhibit central nervous system axonogenesis and synaptogenesis: slit homologue 2 (SLIT2, fully adjusted β −0.34, P<0.001), carbohydrate sulfotransferase 12 (CHSTC, fully adjusted β −0.33, P<0.001), and peptidyl-glycine α-amidating monooxygenase (AMD, fully adjusted β −0.32, P<0.001). These proteins were associated with increased dementia risk, with the fully adjusted hazard ratio per 1 SD being 1.16 (95% confidence interval 1.05 to 1.28) for SLIT2, 1.13 (1.00 to 1.27) for CHSTC, and 1.04 (0.97 to 1.13) for AMD.ConclusionsThe risk of dementia in old age was found to be lower in people with cognitively stimulating jobs than in those with non-stimulating jobs. The findings that cognitive stimulation is associated with lower levels of plasma proteins that potentially inhibit axonogenesis and synaptogenesis and increase the risk of dementia might provide clues to underlying biological mechanisms.

ObjectiveTo compare established associations between risk factors and mortality in UK Biobank, a study with an exceptionally low rate of response to its baseline survey, against those from representative studies that have conventional response rates.DesignProspective cohort study alongside individual participant meta-analysis of other cohort studies.SettingUnited Kingdom.ParticipantsAnalytical sample of 499 701 people (response rate 5.5%) in analyses in UK Biobank; pooled data from the Health Surveys for England (HSE) and the Scottish Health Surveys (SHS), including 18 studies and 89 895 people (mean response rate 68%). Both study populations were linked to the same nationwide mortality registries, and the baseline age range was aligned at 40-69 years.Main outcome measureDeath from cardiovascular disease, selected malignancies, and suicide. To quantify the difference between hazard ratios in the two studies, a ratio of the hazard ratios was used with HSE-SHS as the referent.ResultsRisk factor levels and mortality rates were typically more favourable in UK Biobank participants relative to the HSE-SHS consortium. For the associations between risk factors and mortality endpoints, however, close agreement was seen between studies. Based on 14 288 deaths during an average of 7.0 years of follow-up in UK Biobank and 7861 deaths over 10 years of mortality surveillance in HSE-SHS, for cardiovascular disease mortality, for instance, the age and sex adjusted hazard ratio for ever having smoked cigarettes (versus never) was 2.04 (95% confidence interval 1.87 to 2.24) in UK Biobank and 1.99 (1.78 to 2.23) in HSE-SHS, yielding a ratio of hazard ratios close to unity (1.02, 0.88 to 1.19). The overall pattern of agreement between studies was essentially unchanged when results were compared separately by sex and when baseline years and censoring dates were aligned.ConclusionDespite a very low response rate, risk factor associations in the UK Biobank seem to be generalisable.

ObjectiveTo examine whether physical inactivity is a risk factor for dementia, with attention to the role of cardiometabolic disease in this association and reverse causation bias that arises from changes in physical activity in the preclinical (prodromal) phase of dementia.DesignMeta-analysis of 19 prospective observational cohort studies.Data sourcesThe Individual-Participant-Data Meta-analysis in Working Populations Consortium, the Inter-University Consortium for Political and Social Research, and the UK Data Service, including a total of 19 of a potential 9741 studies.Review methodThe search strategy was designed to retrieve individual-participant data from prospective cohort studies. Exposure was physical inactivity; primary outcomes were incident all-cause dementia and Alzheimer’s disease; and the secondary outcome was incident cardiometabolic disease (that is, diabetes, coronary heart disease, and stroke). Summary estimates were obtained using random effects meta-analysis.ResultsStudy population included 404 840 people (mean age 45.5 years, 57.7% women) who were initially free of dementia, had a measurement of physical inactivity at study entry, and were linked to electronic health records. In 6.0 million person-years at risk, we recorded 2044 incident cases of all-cause dementia. In studies with data on dementia subtype, the number of incident cases of Alzheimer’s disease was 1602 in 5.2 million person-years. When measured <10 years before dementia diagnosis (that is, the preclinical stage of dementia), physical inactivity was associated with increased incidence of all-cause dementia (hazard ratio 1.40, 95% confidence interval 1.23 to 1.71) and Alzheimer’s disease (1.36, 1.12 to 1.65). When reverse causation was minimised by assessing physical activity ≥10 years before dementia onset, no difference in dementia risk between physically active and inactive participants was observed (hazard ratios 1.01 (0.89 to 1.14) and 0.96 (0.85 to 1.08) for the two outcomes). Physical inactivity was consistently associated with increased risk of incident diabetes (hazard ratio 1.42, 1.25 to 1.61), coronary heart disease (1.24, 1.13 to 1.36), and stroke (1.16, 1.05 to 1.27). Among people in whom cardiometabolic disease preceded dementia, physical inactivity was non-significantly associated with dementia (hazard ratio for physical activity assessed >10 before dementia onset 1.30, 0.79 to 2.14).ConclusionsIn analyses that addressed bias due to reverse causation, physical inactivity was not associated with all-cause dementia or Alzheimer’s disease, although an indication of excess dementia risk was observed in a subgroup of physically inactive individuals who developed cardiometabolic disease.

ObjectivesTo examine the association between the Life Simple 7 cardiovascular health score at age 50 and incidence of dementia.DesignProspective cohort study.SettingCivil service departments in London (Whitehall II study; study inception 1985-88).Participants7899 participants with data on the cardiovascular health score at age 50.ExposuresThe cardiovascular health score included four behavioural (smoking, diet, physical activity, body mass index) and three biological (fasting glucose, blood cholesterol, blood pressure) metrics, coded on a three point scale (0, 1, 2). The cardiovascular health score was the sum of seven metrics (score range 0-14) and was categorised into poor (scores 0-6), intermediate (7-11), and optimal (12-14) cardiovascular health.Main outcome measureIncident dementia, identified through linkage to hospital, mental health services, and mortality registers until 2017.Results347 incident cases of dementia were recorded over a median follow-up of 24.7 years. Compared with an incidence rate of dementia of 3.2 (95% confidence interval 2.5 to 4.0) per 1000 person years among the group with poor cardiovascular health, the absolute rate differences per 1000 person years were −1.5 (95% confidence interval −2.3 to −0.7) for the group with intermediate cardiovascular health and −1.9 (−2.8 to −1.1) for the group with optimal cardiovascular health. Higher cardiovascular health score was associated with a lower risk of dementia (hazard ratio 0.89 (0.85 to 0.95) per 1 point increment in the cardiovascular health score). Similar associations with dementia were observed for the behavioural and biological subscales (hazard ratios per 1 point increment in the subscores 0.87 (0.81 to 0.93) and 0.91 (0.83 to 1.00), respectively). The association between cardiovascular health at age 50 and dementia was also seen in people who remained free of cardiovascular disease over the follow-up (hazard ratio 0.89 (0.84 to 0.95) per 1 point increment in the cardiovascular health score).ConclusionAdherence to the Life Simple 7 ideal cardiovascular health recommendations in midlife was associated with a lower risk of dementia later in life.