Brain changes in ageing

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  • Ageing (brain changes)
    • Grey matter
      • Grey matter in the brain begins to decline from the early age of 20 (Ge et al, 2002)
      • Structural neuroimaging studies have shown a significant negative correlation between age and grey matter volume (Good et al, 2001)
      • Significant correlation between grey matter volume and several cerebrovasular risk factors such as systolic blood pressure and BMI (Taki et al, 2011)
      • Grey matter volume decline found in patients with several diseases such as Alzheimer's (Rombouts et al, 2000), semantic dementia (Mummery et al, 2000), and depression (Taki et al, 2005)
      • BMI influences grey matter volume + decline (Taki et al, 2011)
      • Obesity associated with decreased grey matter volume in men (Taki et al, 2011)
      • Degenerative changes such as shrinkage or loss of neurons, and loss of dendritic arborisation
      • Age-related loss of grey matter volume is involved with age-related cognitive change (Brickman et al, 2007)
      • Greatest effects in the frontal lobe (Allen et al, 2005)
    • Brain size
      • Volume of the brain declines with age at a rate of 5% per decade after the age of 40 (Svennerholm et al, 1997)
      • In individuals with very mild dementia, atrophy rate of brain volume is more than double that of age-matched normal elderly people (Fotenos et al, 2005)
      • Shrinkage particularly in the frontal cortex (Peters, 2006)
      • Shrinkage rate increases with age and increase after about age 50
    • Risk factors
      • Obesity
        • Associated with poor cognitive function (Jeong et al, 2005)
        • Risk factor for Alzheimer's disease (Gustafson et al, 2003)
        • Age-related neuronal loss appears to be accelerated by a number of vascular factors that increase ischemia. Obesity has been related to ischemia and to a variety of vascular pathologies that could be related to atrophy
        • May lead to increased cortisol secretion (Bjorntorp, 2001) which can lead to brain volume decrease
      • Smoking heightens risk of vascular disorders that can cause stroke, and constricts arteries that deliver oxygen to the brain
      • Cortisol, the stress hormone, damages the brain over time. Socialising in old age may be protective by lessening stress
    • White matter
      • Brain ageing is marked by degradation of white matter including myelin pallor, loss of myelinated fibres, and malformation of myelin sheaths (Gunning-Dixon et al, 2009)
      • Presence of white matter hyperintensities is common among normal elderly adults
      • Vascular risk factors, such as hypertension accounts for much variability in severity of white matter hyperintensities
      • Relative frontal lobe white matter volume mediated the association between age and performance on tasks of memory and executive functions (Brickman et al, 2006)
      • Severity of white matter hyperintensities is associated with poorer performance in age-sensitive domains like executive function, episodic memory and processing speed (Gunning-Dixon & Raz, 2000)
      • Several longitudinal studies support the role of white matter hyperintensities in age-related declines in executive skills (Kramer et al, 2007)
      • Increase subcortical white matter lesions associated with decreased executive function (Anderton, 2002)
      • White matter lesions increase with age and are associated with increased cardio-vascular risk, reduction in cerebral blood flow, cerebral reactivity, and vascular density, and poor cognition

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