AGEING-BIOPSYCH-REPORT.docx

**AGEING: A BIOLOGICAL AND PSYCHOLOGICAL PERSPECTIVE** Professor Claire Gibson and Professor Harriet Allen What is ageing? Ageing is a gradual, continuous process that begins in early adulthood, characterized by natural and inevitable changes. Table 6.1. Advantages and disadvantages of different...

**AGEING: A BIOLOGICAL AND PSYCHOLOGICAL PERSPECTIVE** Professor Claire Gibson and Professor Harriet Allen What is ageing? Ageing is a gradual, continuous process that begins in early adulthood, characterized by natural and inevitable changes. Table 6.1. Advantages and disadvantages of different methodological approaches to study ageing. +-----------------+-----------------+-----------------+-----------------+ | Study Type | Description | Advantages | Disadvantages | +=================+=================+=================+=================+ | Longitudinal | Data is | Easier to | Participant | | | collected from | control from | dropout rates | | | the same | the cohort | increase over | | | participants | effects as only | time. | | | repeatedly at | one group | | | | different | involved | Resource | | | points over | | intensive to | | | time. | Requires | conduct studies | | | | (relatively) | over long | | | | fewer | periods of | | | | participants | time. | | | | | | | | | | Practice | | | | | effects | +-----------------+-----------------+-----------------+-----------------+ | Cross-sectional | Data is | Efficient -- | Difficult to | | | collected at a | all data | match age | | | single time | collection | groups. | | | point for more | completed | | | | than cohort. | within a | Differences due | | | | relatively | to cohort/ | | | Cohorts are | short time | historical | | | separated into | frame, studies | differences in | | | age groups. | can be easily | environment, | | | | replicated. | economy etc | +-----------------+-----------------+-----------------+-----------------+ | Sequential | Two or more | Repeating or | Complex to | | longitudinal/ | longitudinal, | replicating | plan. | | | or cross | helps separate | | | Sequential | sectional | cohort effects | Can be | | cross sectional | designs, | from age | expensive | | | separated by | effects. | | | | time | | | +-----------------+-----------------+-----------------+-----------------+ | Accelerated | A wide age | Longitudinal | Does not | | longitudinal | range is | data is | completely | | | recruited, | collected from | avoid cohort | | | split into | the same | effects. | | | groups and each | participants | | | | group is | over time. | | | | followed by a | Cross- | | | | few years. | | | | | | sectional data | | | | | collection | | | | | occurs within | | | | | shorter time | | | | | frame. | | +-----------------+-----------------+-----------------+-----------------+ **Methodological considerations for ageing studies** There are a number of issues that are important to consider when studying ageing. Many of these occur because it is difficult, or impossible, to separate out the effects of ageing from the effects of living longer or being born at a different time. Older people will have experienced more life events. This will be true even if the chances of experiencing something are the same throughout life and not related to age. People of different ages have lived at different times, and thus experienced different social, economic and public health factors. The older people get, the more variable their paths through life become. Non-psychological effects can directly impact on psychology. A good example of this is attention. Generalised effects such as slowing need to be controlled for or considered before proposing more complex or subtle effects. **Biological basis of ageing** Ageing per se involves numerous physical, biochemical, vascular, and psychological changes which can be clearly identified in the brain. Magnetic Resonance Imaging (MRI) studies allow the study of specific areas of brain atrophy with age and show that decreases in both grey and white matter occur, albeit at different stages of the lifespan (for further information see Farokhian et al., 2018).  **Brain plasticity and changes to neural circuits** During normal ageing humans, and other animals, experience cognitive decline even in the absence of disease. Neuruplasticity refers to the brain\'s ability to adapt and modify its structure and functions in response to stimuli. Synaptic changes, thought to be a major contributor to age related cognitive decline, involve dendritic alterations in that dendrites shrink, their branching becomes less complex, and they lose dendritic spines. **Cellular and physiological changes** Certain pathological features, in particular the occurrence of beta amyloid (Ab) plaques (sometimes referred to as senile plaques) anal neurofibrillary tangles, are typically associated with dementia-causing diseases such as Alzheimer\'s. However, it is important to note that they also occur with ageing, albeit in smaller amounts, and are more diffusely located compared to disease- pathology, but may also contribute to cell death and disruption in neuronal function seen in ageing. Other physiological changes which occur with ageing, all of which have been suggested to result in cognitive impairment, include oxidative stress, inflammatory reactions and changes in the cerebral microvasculature. Oxidative stress is the damage caused to cells by free radicals that are released during normal metabolic processes. However, compared to other tissues in the body, the brain is particularly sensitive to oxidative stress, which causes DNA damage and inhibits DNA repair processes. Such damage accumulates over the lifespan resulting in cellular dysfunction and death. Ageing is associated with a persistent level of systemic inflammation - this is characterised by increased concentration in the blood of pro-inflammatory cytokines and other chemokines which play a role in producing an inflammatory state, along with increased activation of microglia aml macrophages. Microglia are the brain\'s resident immune cells and are typically quiescent until activated by a foreign antigen. Upon activation, they produce pro-inflammatory cytokines to combat the infection, followed by anti-inflammatory cytokines to restore homeostasis. **Neurotransmitter changes** During ageing the brain also experience changes in the levels of neurotransmitters and their receptors in different regions of the brain largely, but not exclusively, involving the dopamine, serotonin and glutamate systems. Neurochemical changes associated with ageing are important to understand as they may be relevant when considering therapeutic targets aimed at stabilising or enhancing those brain functions which typically deteriorate with age. **Dopamine** is a monoamine neurotransmitter which plays a neuromodulatory role in many CNS functions including executive function, motor control, motivation, arousal, reinforcement and reward. **Serotonin**, also known as 5-hydroxytryptamine (5-HT) functions as both an inhibitory neurotransmitter and a hormone. **Glutamate** is the primary excitatory neurotransmitter in the CNS synthesised by both neuronal and glial cells and high levels of glutamate, causing neurotoxicity, are implicated in a number of neurodegenerative disorders including multiple sclerosis, amyotrophic lateral sclerunts, Alzheimer\'s disease and schizophrenia. **Ageing and genetics** The genetics of human ageing are complex, multifaceted and are based on the assumption that duration of lifespan is, at least in part, genetically determined. **Changes in cognitive systems** The changes in the biological systems and processes above translate into changes across all psychological processes. **Memory** Ageing appears to have greater effects in some types of memory more than others. Memory for personally experienced events (i.e episodic memory) undergoes the clearest decline with age (Ronnlund et al., 2005). **Strategies to promote healthy cognitive ageing** Recently, application of behavioural interventions and non-pharmacological approaches has been demonstrated to improve some aspects of cognitive performance and promote healthy cognitive ageing. **Cognitive or \'brain\' training** - a program of regular mental activities believed to maintain or improve cognitive abilities. **Neuromodulation** - non invasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) have been shown to moderately improve cognitive functioning in older people (Huo et al., 2021) and improve cognitive performance in patients with MCI (Jiang et al., 2021,) tDCS is approved as a safe neuromodulatory technique which delivers a weak, electrical current via electrodes placed on the scalp to directly stimulate cortical targets. **Physical activity**- structured physical activity, in the form of moderate to vigorous aerobic exercise, has been reported to preserve and enhance cognitive functions in older adults. **Attentional control** One example of slowing is that the response to a cue becomes slower with age. A cue can be used to create an alerting response, which increases vigilance and task readiness. A cue can also symbolically direct attention to a specific location. Cues can also capture attention automatically The attention effects above are likely to be due, in part, to other effects of ageing, such as sensory change. Attentional processes are also often measured by visual search tasks. Visual search performance can be used to test multiple attentional mechanisms such as attentional shifting, attention to different features, response times and attentional strategies. Older people show slower performance than younger people for conjunction search, compared to relatively preserved performance in feature-based search(Erel & Levy, 2016). **Inhibition** In contrast to directing attention towards a target, we also need to ignore, avoid or suppress irrelevant actions. \- **Hasher and Zacks (1988)** proposed that an age-related decline in inhibition underlies many differences in performance between older and younger people. **Sensory changes with age** Most of us will have noticed someone reading glasses, or turning up the TV to better hear the dialogue in a favourite film or drama. **Vision** With age there are changes in the eye and in the visual pathways in the brain. **Hearing** As with vision, the effects of age on hearing include declines in the ear as well as in the brain. **Touch** Touch perception is perhaps the least well understood sense when it comes to ageing. **Taste and Smell** Taste and smell are critically important for quality of life and health and also show decline with ageing. **Key Takeaways** Ageing causes natural and inevitable changes in both brain structure and function- however, we don\'t yet fully understand the rate of change and the processes involved. Changes to the brain which may affect cognitive and sensory functions occur at molecular, synaptic and cellular levels - some of which, but not all, is driven by genetic factors. Understanding the mechanisms of ageing is important as this may identify approaches to try and alleviate age-related decline in cognition and sensory functions, along with identifying psychological and lifestyle factors which may help promote healthy cognitive ageing.