Who uses it and who loses it? Personality, activity engagement and cognitive health in old age

Identifying strategies to promote cognitive health in older age is a key research priority as older adults continue to make up a growing proportion of the global population. The ‘use it or lose it’ theory proposes that leading a more active, engaged lifestyle can be cognitively protective. Cross-sectional studies provide support for this, with evidence suggesting that older adults who are mentally, physically, socially and creatively active in their everyday lives may also have higher levels of cognitive ability and experience lower levels of cognitive decline. Intervention studies can provide further insight, going beyond cross-sectional associations to explore causality by testing the effect of increased engagement in an experimental paradigm. It is essential that such interventions consider the importance of individual differences; in particular, evidence suggests that individual differences in personality might predict activity engagement, and in turn cognitive health. It is therefore possible that individual differences in personality might influence engagement level within an intervention, and in turn the degree of benefit received. The PhD research reported in the present thesis examined these possibilities using data collected from a large-scale, activity-based intervention study known as The Intervention Factory. This study tested the cognitive benefits of activity engagement in a more real-world environment by using existing, community based classes and groups. A sample of 336 adults aged 65 and over without any diagnosed cognitive impairments were recruited and completed baseline assessments. Cross-sectional data at baseline were used to examine whether lifestyle variables such as activity engagement mediated any associations between Big Five personality traits and cognitive ability across several domains. Higher Openness to Experience and lower Neuroticism and Extraversion predicted higher levels of cognitive performance, but there was no evidence to suggest these associations were mediated by activity engagement. The PhD research then examined whether personality might influence activity engagement and cognitive change within the context of an intervention. A systematic review of the literature found ten studies that had previously explored this question; there was some evidence that higher Openness to Experience was linked to greater cognitive gains when studies used novel intervention methods. This theory was then tested within the context of The Intervention Factory specifically. Participants were pseudo-randomly allocated to one of five activity groups (computer classes, dance/exercise/sport classes, social/bingo groups, language classes or handicraft/woodcraft classes) or a no-contact control group and attended their activity for around ten weeks. None of the activity groups showed evidence of significantly greater cognitive improvements compared to the control group over the course of the intervention. There was also no reliable evidence that individual personality traits predicted adherence or moderated intervention-related cognitive change. While these results did not support the efficacy of real-world activities to promote cognitive health, several challenges were identified that will inform and encourage future research in this area. These challenges included issues arising from non-random group allocation, difficulty recruiting an effective control group and variability in intervention delivery when translated to a more real-world setting. Addressing these challenges in future studies will provide further opportunities to explore the potential cognitive benefits of real world activities, and whether any benefits vary at the individual level

Addressing fractional dimensionality in the application of weather index insurance and climate risk financing in agricultural development: A dynamic triggering approach

Climate risk financing programs in agriculture have caught the attention of researchers and policy makers over the last decade. Weather index insurance has emerged as a promising market-based risk financing mechanism. However, to develop a suitable weather index insurance mechanism it is essential to incorporate the distribution of underlying weather and climate risks to a specific event model that can minimize intra-seasonal basis risk. In this paper we investigate the erratic nature of rainfall patterns in Kenya using CHIRPS rainfall data from 1983-2017. We find that the patterns of rainfall are fractional, both erratic and persistent which is consistent with the Noah and Joseph effects well known in mathematics. The erratic nature of rainfall emerges from the breakdown of the convergence to a normal distribution. Instead we find that the distribution about the average is approximately lognormal, with an almost 50% higher chance of deficit rainfall below the mean versus adequate rainfall above the mean. We find that the rainfall patterns obey Hurst law and the measured Hurst coefficients for seasonal rainfall pattern across all years range from a low of 0.137 to a high above 0.685. To incorporate the erratic and persistent nature of seasonal rainfall, we develop a new approach to weather index insurance based upon the accumulated rainfall in any 21-day period falling below 60% of the long-term average for that same 21-day period. We argue that this approach is more satisfactory to matching drought conditions within and between various phenological stages of growth

An Observational Cohort Study of Longitudinal Impacts on Frailty and Well-Being of COVID-19 Lockdowns in Older Adults in England and Spain

To reduce the spread of COVID-19, governments initiated lockdowns, limiting mobility and social interaction of populations. Lockdown is linked to health issues, yet the full impact on health remains unknown, particularly in more vulnerable groups. This study examined impact on frailty and outcomes in high and low COVID-19 risk older adults. We examined health-related behaviours and support resources participants used during lockdown(s). Lockdown impacts in two countries were compared across four time points to examine impacts of different rules. We recruited 70 participants (aged >70 years) in England and Spain. Participants were allocated to higher or lower COVID-19-risk groups based on UK NHS guidelines. They completed assessments for frailty, quality-of-life, loneliness, exercise frequency and social interaction, coping resources and perception of age-friendliness of their environment. The four assessments took place over a 7-month period. Frailty was highest at Time 1 (most severe lockdown restrictions) and significantly higher in the Spanish group. It was lower at Time 3 (lowest restrictions), but did not continue to reduce for the English participants. Perceptions of the age friendliness of the environment matched these changes. Coping resources did not mitigate changes in frailty and outcomes over time, but more frequent physical activity predicted more reduction in frailty. Lockdown had a negative impact on frailty, increasing risk of adverse events for older people, but recovery once lockdowns are eased is evidenced. Further research is required to consider longer term impacts and methods to mitigate effects of lockdown on health

Heterogeneous demand and supply for an insurance-linked credit product in Kenya: A stated choice experiment approach

We employ a discrete choice experiment to elicit demand and supply side preferences for insurance- linked credit, a promising market-based tool for managing agricultural weather risks and providing access to credit for farmers. We estimate preference heterogeneity using primary data from smallholder farmers and managers of lenders/insurers combined with household socio-economic survey data in Kenya. We analyse the choice data using maximum simulated likelihood and Hierarchical Bayes estimation of a mixed logit model. Although there are some similarities, we find that there is conflicting demand and supply side preferences for credit terms, collateral requirements, and loan use flexibility. We also analyse willingness to buy and willingness to offer for farmers and suppliers, respectively for the risk premium for different attributes and their levels. Identifying the preferred attributes and levels for both farmers and financial institutions can guide optimal packaging of insurance and credit providing market participation and adoption motivation for insurance-bundled credit product

Personality and Cognitive Ability in Older Age: Investigating the Mediating Role of an Active and Healthy Lifestyle

R analysis code for the manuscript 'Personality and Cognitive Ability in Older Age: Investigating the Mediating Role of an Active and Healthy Lifestyle

Does apolipoprotein E genotype moderate the association between physical activity and brain health? A systematic review and meta-analysis

Introduction: Possession of one or two e4 alleles of the apolipoprotein E (APOE) gene is associated with cognitive decline and dementia risk. Some evidence suggests that physical activity may benefit carriers of the e4 allele differently. Method: We conducted a systematic review and meta-analysis of studies which assessed APOE differences in the association between physical activity and: lipid profile, Alzheimer’s disease pathology, brain structure and brain function in healthy adults. Searches were carried out in PubMed, SCOPUS, Web of Science and PsycInfo. Results: Thirty studies were included from 4896 papers screened. Carriers of the e4 allele gained the same benefit from physical activity as non-carriers on most outcomes. For brain activation, e4 carriers appeared to gain a greater benefit from physical activity in activation and functional connectivity compared to non-carriers. Post hoc analysis identified possible compensatory mechanisms allowing e4 carriers to maintain cognitive function. Discussion: Though there is evidence suggesting physical activity may benefit e4 carriers differently compared to non-carriers, this may vary by the specific brain health outcome, perhaps limited to brain activation. Further research is required to confirm these findings and elucidate the mechanisms