Michelle D. Taylor

The Lothian Birth Cohort 1936: a study to examine influences on cognitive ageing from age 11 to age 70 and beyond.

BackgroundCognitive ageing is a major burden for society and a major influence in lowering peoples independence and quality of life. It is the most feared aspect of ageing. There are large individual differences in age-related cognitive changes. Seeking the determinants of cognitive ageing is a research priority. A limitation of many studies is the lack of a sufficiently long period between cognitive assessments to examine determinants. Here, the aim is to examine influences on cognitive ageing between childhood and old age.Methods/DesignThe study is designed as a follow-up cohort study. The participants comprise surviving members of the Scottish Mental Survey of 1947 (SMS1947; N = 70,805) who reside in the Edinburgh area (Lothian) of Scotland. The SMS1947 applied a valid test of general intelligence to all children born in 1936 and attending Scottish schools in June 1947. A total of 1091 participants make up the Lothian Birth Cohort 1936. They undertook: a medical interview and examination; physical fitness testing; extensive cognitive testing (reasoning, memory, speed of information processing, and executive function); personality, quality of life and other psycho-social questionnaires; and a food frequency questionnaire. They have taken the same mental ability test (the Moray House Test No. 12) at age 11 and age 70. They provided blood samples for DNA extraction and testing and other biomarker analyses. Here we describe the background and aims of the study, the recruitment procedures and details of numbers tested, and the details of all examinations.DiscussionThe principal strength of this cohort is the rarely captured phenotype of lifetime cognitive change. There is additional rich information to examine the determinants of individual differences in this lifetime cognitive change. This protocol report is important in alerting other researchers to the data available in the cohort.

Childhood IQ, social class, deprivation, and their relationships with mortality and morbidity risk in later life: Prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies

Objective To investigate how childhood mental ability (IQ) is related to mortality and morbidity risk, when socioeconomic factors are also considered. Methods Participants were from the Midspan studies conducted on adults in the 1970s; 938 Midspan participants were successfully matched with the Scottish Mental Survey 1932 in which children born in 1921 and attending Scottish schools on June 1, 1932, took a cognitive ability test. Mortality, hospital admissions, and cancer incidence in the 25 years after the Midspan screening were investigated in relation to childhood IQ, social class, and deprivation. Results The risk of dying in 25 years was 17% higher for each standard deviation disadvantage in childhood IQ. Adjustment for social class and deprivation category accounted for some, but not all, of this higher risk, reducing it to 12%. Analysis by IQ quartile showed a substantial increased risk of death for the lowest-scoring quarter only. Structural equation modeling indicated that the effect of childhood IQ on mortality was partly indirectly influenced by social factors. Cause-specific mortality or hospital admission showed that lower IQ was associated with higher risks for all cardiovascular disease and coronary heart disease. Cause-specific mortality or cancer incidence risk was higher with decreasing IQ for lung cancer. Conclusions Lower childhood IQ was related to higher mortality risk and some specific causes of death or morbidity. Childhood IQ may be considered as a marker for risk of death or illness in later life in similar and complementary ways to social class or deprivation category.

Neuroticism, extraversion, and mortality in the UK health and lifestyle survey : A 21-year prospective cohort study

Objective: To examine the influence of neuroticism and extraversion on all-cause and cause-specific mortality over 21 years after controlling for risk factors. Methods: Participants were members of the Health and Lifestyle Survey, a British nationwide sample survey of 9003 adults. At baseline (1984 to 1985), individuals completed a sociodemographic and health questionnaire, underwent physical health examination, and completed the Eysenck Personality Inventory. Mortality was assessed for 21 years after baseline. A total of 5424 individuals had complete data. Results: After controlling for age and gender, 1-standard deviation (SD) increase in neuroticism was related to 9% (hazard ratio (HR) = 1.09; 95% Confidence Interval (CI) = 1.03–1.16) increased risk of mortality from all causes. The association was nonsignificant (HR = 1.05; 95% CI = 0.99–1.11) after additionally controlling for occupational social class, education, smoking, alcohol consumption, physical activity, and health. There was 12% (HR = 1.12; 95% CI = 1.03–1.21) increased risk of death from cardiovascular disease associated with 1-SD increase in neuroticism. This was still significant after adjustment. When the sample was divided into 40- to 59-year-olds and those ≥60 years, neuroticism remained a significant risk for all-cause mortality and cardiovascular disease mortality; associations were nonsignificant after controlling for all covariates. Neuroticism was not associated with deaths from stroke, respiratory disease, lung cancer, or other cancers. Extraversion was protective of death from respiratory disease (HR = 0.84; 95% CI = 0.70– 1.00). Conclusions: After controlling for several risk factors, high neuroticism was significantly related to risk of death from cardiovascular disease. The effects of neuroticism on death from cardiovascular disease may be mediated by sociodemographic, health behavior, and physiological factors. EPI = Eysenck Personality Inventory; HR = hazard ratio; CI = Confidence Interval; HALS = Health and Lifestyle Survey; CVD = cardiovascular disease; CHD = coronary heart disease; BMI = body mass index; BP = blood pressure; FEV = forced expiratory volume.

Cognition and all-cause mortality across the entire adult age range : Health and lifestyle survey

Objective: To investigate the association of reaction time and brief measures of memory and spatial ability with all-cause mortality. Methods: Participants were from the UK Health and Lifestyle Survey (HALS), a national sample survey of adults in England, Scotland, and Wales. In 1984/1985, data on lifestyle factors, socioeconomic status, and health were collected for 9,003 people. Cognitive data were collected for 7,414 individuals. All-cause mortality was investigated over 19 years of follow-up in relation to simple and choice reaction time, performance on a short-term verbal declarative memory test, and on a test of visual-spatial reasoning. Results: Slower and more variable simple and choice reaction times were significantly related to increased risk of all-cause mortality over 19 years of follow-up. The increased risk of all-cause mortality was partly attenuated after adjustments for socioeconomic status, health behaviors, and health status. A novel finding was the existence of an effect of reaction time on all-cause mortality in young adults. Poorer verbal memory ability was also significantly related to an increased risk of dying in young adults independently of reaction time score. Conclusion: Slower and more variable reaction time was related to higher mortality risk in younger as well as older participants. Among younger adults, higher memory ability was also associated with lower risk of dying. The cognition-mortality relationship may be explained in part by the brain’s efficiency of information processing and memory performance. HALS = Health and Lifestyle Survey; FEV = forced expiratory volume; BMI = body mass index.

Five factor model personality traits and all-cause mortality in the Edinburgh Artery Study cohort.

Objective: To examine whether personality traits are related to all-cause mortality in a general adult population in Scotland. Methods: The Edinburgh Artery Study began in 1987 to 1988 by recruiting 1592 men and women aged 55 to 74 years to be followed-up for atherosclerotic diseases. The NEO Five-Factor Inventory (NEO-FFI) was completed by 1035 surviving participants in 1995 to 1996. Deaths from all causes were examined in relation to personality traits and social and physical risk factors for mortality. Results: During follow-up, 242 (37.1%) men and 165 (24.6%) women died. For the whole sample, there was a 28% lower rate of all-cause mortality for each 1 SD increase in NEO-FFI openness (95% CI, 0.61–0.84) and a 18% lower rate of all-cause mortality for each 1 SD increase in NEO-FFI conscientiousness (95% CI, 0.70–0.97). In men, the risk of all-cause mortality was 0.63 (95% CI, 0.5–10.78) for a 1 SD increase in openness and 0.75 (95% CI, 0.61–0.91) for a 1 SD increase in conscientiousness. In women, none of the personality domains were significantly associated with all-cause mortality. Well fitting structural equation models in men (n = 652) showed that the relationships between conscientiousness and openness and all-cause mortality were not substantially explained by smoking, or other variables in the models. Conclusion: High conscientiousness and openness may be protective against all-cause mortality in men. Further investigations are needed on the mechanisms of these associations, and the influence of personality traits on specific causes of death. BMI = body mass index; SBP = systolic blood pressure; NEO-FFI = NEO Five-Factor Inventory.

Smoking and cognitive change from age 11 to age 80

Age related cognitive decline affects people’s quality of life and their ability to live independently.1 A recent review stated, “[we] are aware of no studies on the relationship between smoking and cognitive decline associated with normal aging or studies of the effect of smoking on cognition in normally aging individuals.”1 Some previous studies examined smoking in relation to pathological cognitive aging, but lacked cognitive data before the initiation of smoking, and used crude clinical cognitive assessments.2–4 Among middle aged subjects, current smoking was associated with poorer cognitive performance on tasks of psychomotor speed and cognitive flexibility.5 Smoking has been identified as a possible risk factor for accelerated cerebral degenerative changes, cognitive decline, and dementia.6 Here we show that smoking contributes to normal cognitive change from age 11 to age 80. The Scottish Mental Survey of 1932 (SMS1932) tested mental ability in people born in 1921 (n = 87 498). The SMS1932’s Moray House test (MHT) was validated against the Stanford Binet test and includes verbal reasoning, numerical, spatial, and …

Cognition and mortality from the major causes of death : the Health and Lifestyle Survey

OBJECTIVE To investigate the influence of reaction time and cognition on the risk of death from cause-specific mortality and to examine whether any association found remains after adjustment for available socioeconomic, lifestyle, and health factors. METHODS Participants were from the UK Health and Lifestyle Survey. The sample consisted of 6424 community dwelling individuals aged between 18 and 97 years at baseline (1984/1985). Sociodemographic, lifestyle, health, and physiological information was collected alongside cognitive testing which included simple (SRT) and choice (CRT) reaction time, a short-term memory test, and a test of visual-spatial reasoning. Participants have been followed for 21 years for cause-specific mortality. RESULTS Slower and more variable reaction times and poorer cognitive performance were associated with a higher risk of death from cardiovascular disease, stroke, and respiratory disease after controlling for age and sex. Slight attenuation was noted after adjustments for all covariates. However, only CRT mean remained significantly associated with death from respiratory disease. No associations were found for coronary heart disease, lung cancer, and all nonlung cancers. Significant cognition-mortality associations were mostly obtained in those aged over 60 years. The possibility of reverse causality was partly excluded by reanalysing the data after omitting individuals who died within 5 years of cognitive testing. CONCLUSIONS Slower and more variable reaction times and poorer cognitive performance were related to an increased risk of mortality from cardiovascular disease, stroke, and respiratory disease. The possibility of reverse causality requires further testing.

The Scottish Mental Survey 1932 linked to the Midspan studies: a prospective investigation of childhood intelligence and future health

The Scottish mental survey of 1932 (SMS1932) recorded mental ability test scores for nearly all children born in 1921 and at school in Scotland on 1 June 1932. The Collaborative and Renfrew/Paisley studies, two of the Midspan studies, obtained health and social data by questionnaire and a physical examination in the 1970s. Some Midspan participants were born in 1921 and may also have taken part in the SMS1932, so there was a possibility that their mental ability data from childhood would be available. The 1921 born Midspan participants were matched with the computerized SMS1932 database, and in total, 1032 of 1251 people (82.5%) were matched successfully. Of those matched, 938 (90.9%) had a mental ability test score recorded. The mean score of the matched sample was 37.2 (standard deviation (SD) 13.9) out of a possible score of 76. The mean (SD) for the boys and girls was 38.3 (14.2) and 35.7 (13.9), respectively. This compared with 38.6 (15.7) and 37.2 (14.3) for boys and girls in all of Scotland. Graded relationships were found between mental ability in childhood, and social class and deprivation category of residence in adulthood. Being in a higher social class or in a more affluent deprivation category was associated with higher childhood mental ability scores, and the scores reduced with increasing deprivation. Future plans for the matched data include examining associations between childhood mental ability and other childhood and adult risk factors for disease in adulthood, and modelling childhood mental ability, alongside other factors available in the Midspan database, as a risk factor for specific illnesses, admission to hospital and mortality.

Association between mortality and cognitive change over 7 years in a large representative sample of UK residents

Objective: To examine the association between change in reaction time and cognitive performance over 7 years and the risk of death from all causes and some specific causes after controlling for known risk factors. Methods: The sample comprised members of the Health and Lifestyle Survey (HALS) of community-dwelling adults in England, Scotland, and Wales. Baseline testing (HALS1), involving 9003 people, took place in 1985 and 1986. Sociodemographic, lifestyle, health, and physiological information was collected. Cognitive functioning was measured using tests of simple and choice reaction time, a short memory test, and a test of visual-spatial reasoning. Follow-up testing (HALS2) took place in 1991 and 1992, when 5352 members of the study were administered the same questionnaires, physiological examinations, and cognitive tests. The sample has been followed for mortality up to June 2005. Results: After controlling for age, gender, and the relevant baseline cognitive test scores, greater declines between HALS1 and HALS2 on simple reaction time mean and variability, choice reaction time mean and variability, memory and visual-spatial reasoning were associated with significantly increased risks of death from all causes, all cardiovascular diseases (CVDs), coronary heart disease (CHD), stroke, and respiratory disease. These associations were only slightly attenuated after adjusting for occupational social class, educational, smoking, alcohol consumption, physical activity, body mass index, blood pressure, and lung function. Conclusions: Decline in performance of reaction times and simple cognitive tasks across a 7-year period was associated with an increased risk of death from all causes, all CVDs, CHD, stroke, and respiratory disease up to 13 years later, even after adjustment for known risk factors. RT = reaction time; HR = hazard ratio; CI = 95% confidence interval; HALS = Health and Lifestyle Survey; CVD = cardiovascular disease; CHD = coronary heart disease; BMI = body mass index; BP = blood pressure; FEV = forced expiratory volume; SRT = simple reaction time; CRT = choice reaction time.

Childhood IQ and social factors on smoking behaviour, lung function and smoking-related outcomes in adulthood: Linking the Scottish Mental Survey 1932 and the Midspan Studies

OBJECTIVE To investigate the associations of childhood IQ and adult social factors, and smoking behaviour, lung function (forced expiratory volume in one second; FEV(1)), and smoking-related outcomes in adulthood. DESIGN Retrospective cohort study. METHOD Participants were from the Midspan prospective studies conducted on Scottish adults in the 1970s. The sample consisted of 938 Midspan participants born in 1921 who were successfully matched with their cognitive ability test results on the Scottish Mental Survey 1932. RESULTS Structural equation modelling showed that age 11 IQ was not directly associated with smoking consumption, but that IQ and adult social class had indirect effects on smoking consumption via deprivation category. The influence of IQ on FEV(1) was partly indirect via social class. Gender influenced smoking consumption and also IQ and social class. There was a 21% higher risk of having a smoking-related hospital admission, cancer, or death during 25 years of follow-up for each standard deviation disadvantage in IQ. Adjustment for adult social class, deprivation category, and smoking reduced the association to 10%. CONCLUSION Childhood IQ was associated with social factors which influenced lung function in adulthood, but was not associated directly with smoking consumption. In future studies, it is important to consider other pathways which may account for variance in the link between childhood IQ and health in later life.