Renal function and cognition in the 1932 Scottish Mental Survey Lothian cohort

Healthy cognitive ageing in the Lothian Birth Cohort studies: marginal gains not magic bullet

In the face of shifting demographics and an increase in human longevity, it is important to examine carefully what is known about cognitive ageing, and to identify and promote possibly malleable lifestyle and health-related factors that might mitigate age-associated cognitive decline. The Lothian Birth Cohorts of 1921 (LBC1921, n = 550) and 1936 (LBC1936, n = 1091) are longitudinal studies of cognitive and brain ageing based in Scotland. Childhood IQ data are available for these participants, who were recruited in later life and then followed up regularly. This overview summarises some of the main LBC findings to date, illustrating the possible genetic and environmental contributions to cognitive function (level and change) and brain imaging biomarkers in later life. Key associations include genetic variation, health and fitness, psychosocial and lifestyle factors, and aspects of the brain's structure. It addresses some key methodological issues such as confounding by early-life intelligence and social factors and emphasises areas requiring further investigation. Overall, the findings that have emerged from the LBC studies highlight that there are multiple correlates of cognitive ability level in later life, many of which have small effects, that there are as yet few reliable predictors of cognitive change, and that not all of the correlates have independent additive associations. The concept of marginal gains, whereby there might be a cumulative effect of small incremental improvements across a wide range of lifestyle and health-related factors, may offer a useful way to think about and promote a multivariate recipe for healthy cognitive and brain ageing.

Cognitive and kidney function: results from a British birth cohort reaching retirement age

BACKGROUND

Previous studies have found associations between cognitive function and chronic kidney disease. We aimed to explore possible explanations for this association in the Medical Research Council National Survey of Health and Development, a prospective birth cohort representative of the general British population.

METHODS

Cognitive function at age 60-64 years was quantified using five measures (verbal memory, letter search speed and accuracy, simple and choice reaction times) and glomerular filtration rate (eGFR) at the same age was estimated using cystatin C. The cross-sectional association between cognitive function and eGFR was adjusted for background confounding factors (socioeconomic position, educational attainment), prior cognition, and potential explanations for any remaining association (smoking, diabetes, hypertension, inflammation, obesity).

RESULTS

Data on all the analysis variables were available for 1306-1320 study members (depending on cognitive measure). Verbal memory and simple and choice reaction times were strongly associated with eGFR. For example, the lowest quartile of verbal memory corresponded to a 4.1 (95% confidence interval 2.0, 6.2) ml/min/1.73 m(2) lower eGFR relative to the highest quartile. Some of this association was explained by confounding due to socioeconomic factors, but very little of it by prior cognition. Smoking, diabetes, hypertension, inflammation and obesity explained some but not all of the remaining association.

CONCLUSIONS

These analyses support the notion of a shared pathophysiology of impaired cognitive and kidney function at older age, which precedes clinical disease. The implications of these findings for clinical care and research are important and under-recognised, though further confirmatory studies are required.

Cohort profile: the Lothian Birth Cohorts of 1921 and 1936

This cohort profile describes the origins, tracing, recruitment, testing and follow-up of the University of Edinburgh-based Lothian Birth Cohorts of 1921 (LBC1921; N = 550) and 1936 (LBC1936; N = 1091). The participants undertook a general intelligence test at age 11 years and were recruited for these cohorts at mean ages of 79 (LBC1921) and 70 (LBC1936). The LBC1921 have been examined at mean ages of 79, 83, 87 and 90 years. The LBC1936 have been examined at mean ages of 70 and 73 years, and are being seen at 76 years. Both samples have an emphasis on the ageing of cognitive functions as outcomes. As they have childhood intelligence test scores, the cohorts' data have been used to search for determinants of lifetime cognitive changes, and also cognitive change within old age. The cohorts' outcomes also include a range of physical and psycho-social aspects of well-being in old age. Both cohorts have a wide range of variables: genome-wide genotyping, demographics, psycho-social and lifestyle factors, cognitive functions, medical history and examination, and biomarkers (from blood and urine). The LBC1936 participants also have a detailed structural magnetic resonance imaging (MRI) brain scan. A range of scientific findings is described, to illustrate the possible uses of the cohorts.

Cardiovascular and biochemical risk factors for incident dementia in the Hypertension in the Very Elderly Trial

OBJECTIVES

Several cardiovascular and biochemical factors including hypertension have been associated with cognitive decline and dementia, although both epidemiological and intervention evidence is mixed with the majority of studies examining those in midlife or younger elderly and the recent Hypertension in the Very Elderly Trial showing no significant association between blood pressure lowering and incident dementia. It has also been suggested that risk factors may differ in the very elderly. The aim of these analyses was to examine the impact of baseline cardiovascular and biochemical factors upon incident dementia and cognitive decline in a very elderly hypertensive group.

METHODS

Participants of the Hypertension in the Very Elderly Trial were aged at least 80 years and hypertensive. Cognitive function was assessed at baseline and annually with diagnostic information collected for dementia and relationships between baseline total and high-density lipoprotein cholesterol, creatinine, glucose, haemoglobin, heart failure, atrial fibrillation, diabetes, previous stroke and later dementia/cognitive decline were examined.

RESULTS

There were 3336 participants with longitudinal cognitive function data. In multivariate analyses higher creatinine was associated with a lower risk of incident dementia and cognitive decline. Higher total and lower high-density lipoprotein cholesterol were associated with lower risk of cognitive decline. Other variables were not significant.

CONCLUSIONS

In very elderly hypertensive patients heart failure, diabetes, atrial fibrillation, prior stroke, glucose and haemoglobin levels did not demonstrate a relationship with cognitive decline or dementia. Higher creatinine (excluding moderate renal impairment) was associated with a lower risk of dementia and cognitive decline. The findings for total and high-density lipoprotein cholesterol add to the varied literature in this area and together these findings may add weight to the suggestion that risk factor profiles differ in the very elderly.