Cognitive ability across the life course and cortisol levels in older age

Elevated cortisol levels have been hypothesised to contribute to cognitive ageing, but study findings are inconsistent. In the present study, we examined the association between salivary cortisol in older age and cognitive ability across the life course. We used data from 370 members of the 36-Day Sample of the Scottish Mental Survey 1947, who underwent cognitive testing at age 11, and were then followed up at around age 78, completing further cognitive tests and providing diurnal salivary cortisol samples. We hypothesised that higher cortisol levels would be associated with lower cognitive ability in older age and greater cognitive decline from childhood to older age, but also lower childhood cognitive ability. Few of the tested associations were significant, and of those that were, most suggested a positive relationship between cortisol and cognitive ability. Only one cognitive measure showed any sign of cortisol-related impairment. However, after correcting for multiple comparisons, no results remained significant. These findings suggest that cortisol may not play an important role in cognitive ageing across the life course

The CIRCORT database: Reference ranges and seasonal changes in diurnal salivary cortisol derived from a meta-dataset comprised of 15 field studies

Diurnal salivary cortisol profiles are valuable indicators of adrenocortical functioning in epidemiological research and clinical practice. However, normative reference values derived from a large number of participants and across a wide age range are still missing. To fill this gap, data were compiled from 15 independently conducted field studies with a total of 104,623 salivary cortisol samples obtained from 18,698 unselected individuals (mean age: 48.3 years, age range: 0.5–98.5 years, 39% females). Besides providing a descriptive analysis of the complete dataset, we also performed mixed-effects growth curve modeling of diurnal salivary cortisol (i.e., 1–16 h after awakening). Cortisol decreased significantly across the day and was influenced by both, age and sex. Intriguingly, we also found a pronounced impact of sampling season with elevated diurnal cortisol in spring and decreased levels in autumn. However, the majority of variance was accounted for by between-participant and between-study variance components. Based on these analyses, reference ranges (LC/MS–MS calibrated) for cortisol concentrations in saliva were derived for different times across the day, with more specific reference ranges generated for males and females in different age categories. This integrative summary provides important reference values on salivary cortisol to aid basic scientists and clinicians in interpreting deviations from the normal diurnal cycle

Investigating the Bidirectional Associations of Adiposity with Sleep Duration in Older Adults: The English Longitudinal Study of Ageing (ELSA)

Cross-sectional analyses of adiposity and sleep duration in younger adults suggest that increased adiposity is associated with shorter sleep. Prospective studies have yielded mixed findings, and the direction of this association in older adults is unclear. We examined the cross-sectional and potential bi-directional, prospective associations between adiposity and sleep duration (covariates included demographics, health behaviours, and health problems) in 5,015 respondents from the English Longitudinal Study of Ageing (ELSA), at baseline and follow-up. Following adjustment for covariates, we observed no significant cross-sectional relationship between body mass index (BMI) and sleep duration [(unstandardized) B?=??0.28?minutes, (95% Confidence Intervals (CI)?=??0.012; 0.002), p?=?0.190], or waist circumference (WC) and sleep duration [(unstandardized) B?=??0.10?minutes, (95% CI?=??0.004; 0.001), p?=?0.270]. Prospectively, both baseline BMI [B?=??0.42?minutes, (95% CI?=??0.013; ?0.002), p?=?0.013] and WC [B?=??0.18?minutes, (95% CI?=??0.005; ?0.000), p?=?0.016] were associated with decreased sleep duration at follow-up, independently of covariates. There was, however, no association between baseline sleep duration and change in BMI or WC (p?>?0.05). In older adults, our findings suggested that greater adiposity is associated with decreases in sleep duration over time; however the effect was very small

Mealtime : A circadian disruptor and determinant of energy balance?

Open Access via the Jisc Wiley Agreement Medical Research Council Grant Number(s): MR/P012205/1 Rural and Environment Science and Analytical Services DivisionPeer reviewedPublisher PD

Endogenous insulin secretion in critically ill patients

1-pageGlucose-insulin system models can be used for improved glycemic control of critically ill patients. A key component of glucose-insulin models is pancreatic insulin secretion. There is limited data in the literature quantifying insulin secretion in critically ill patients at physiologic levels. This study presents a model pancreatic insulin secretion in critically ill patients based on data from a critically ill population

Endogenous insulin secretion and suppression during and after sepsis in critically ill patients: implications for tight glycemic control protocols

Introduction: Insulin infusions over 2 U/hr can suppress endogenous insulin secretion in healthy subjects 30-45% [1]. Virtually all tight glycaemic control (TGC) protocols deliver insulin via infusion. This study examines the impact of bolus delivery of insulin in TGC on the endogenous insulin secretion of critically ill patients. Methods: 18 patients from the Christchurch Hospital ICU enrolled in a prospective clinical trial studying sepsis each had two sets of blood samples assayed for insulin and C-peptide. The first set was taken at the commencement of the SPRINT TGC protocol for patients with suspected sepsis. The second set was taken when their SIRS score was consistently below 2. Each set had 4 samples taken at: -1, 10, 40 and 60 min following bolus delivery of insulin as required by SPRINT to capture endogenous insulin secretion during the bolus profile. Bolus size was dictated by the protocol, but was in the range 2-6 units. Model-based methods [2] were used to calculate the endogenous insulin secretion rate for each set of samples. The level of suppression was calculated as the ratio of the secretion rate between 5-15 mins (just after peak plasma insulin) and average of the 0-5 min (basal) and 15-60 min (return to basal) secretion rates identified

Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences and Countermeasures.

Circadian (∼ 24 hour) timing systems pervade all kingdoms of life, and temporally optimize behaviour and physiology in humans. Relatively recent changes to our environments, such as the introduction of artificial lighting, can disorganize the circadian system, from the level of the molecular clocks that regulate the timing of cellular activities to the level of synchronization between our daily cycles of behaviour and the solar day. Sleep/wake cycles are intertwined with the circadian system, and global trends indicate that these too are increasingly subject to disruption. A large proportion of the world's population is at increased risk of environmentally-driven circadian rhythm and sleep disruption, and a minority of individuals are also genetically predisposed to circadian misalignment and sleep disorders. The consequences of disruption to the circadian system and sleep are profound and include myriad metabolic ramifications, some of which may be compounded by adverse effects on dietary choices. If not addressed, the deleterious effects of such disruption will continue to cause widespread health problems; therefore, implementation of the numerous behavioural and pharmaceutical interventions that can help restore circadian system alignment and enhance sleep will be important

Body Weight, Not Insulin Sensitivity or Secretion, May Predict Spontaneous Weight Changes in Nondiabetic and Prediabetic Subjects: The RISC Study

Previous studies have found that high insulin sensitivity predicts weight gain; this association has not been confirmed. Our aim was to systematically analyze metabolic predictors of spontaneous weight changes