Paulina Szlendak, Year 3
According to astounding statistics by alzheimers.org.uk, women with dementia outnumber men 2 to 1 worldwide. What is the cause of such a drastic difference in prevalence? One common hypothesis is that, on average, women live longer than men, and therefore have more time to develop dementia, which is commonly associated with old age (Brinton et al., 2015). While risk does increase with age, the pathophysiology of dementia in relation to gender is much more complex than that. Current research suggests that looking at hormonal changes during menopause is the key to uncovering the mystery of this dementia gender gap (Mishra et al., 2022).
Menopause is a natural stage of life experienced by half of the population worldwide. As of now, there are approximately 850 million women aged 40-60 years old who are likely to be going through or are already past menopause (US Census Bureau, 2014). The neuroendocrine transition of this process often manifests with numerous neurological symptoms: insomnia, depression, hot flashes and loss of cognitive sharpness (Brinton et al., 2015). Unfortunately, all these common symptoms of menopause have been identified as risk factors for dementia, especially Alzheimer’s Disease (AD) (Brinton et al., 2015).
Before we look at why women are at a greater risk of developing dementia and AD, experts in the field of neurological ageing highlight an important change in perception of brain ageing. It was previously thought to be a linear process of steady decline in function, paired with a slow accumulation of toxic compounds. Only recently have scientists realised that ageing of the brain is in fact not linear at all, but a dynamic process. In the female brain there is an important catalyst of this process during midlife (Mishra et al., 2022). Recent studies looking at sex differences in AD development confirm that there are earlier neuro-degenerative changes occuring in female brains than male (Mielke et al., 2014). Moreover, these changes have been linked to the endocrine ageing process physiologically occurring in females during menopause (Mosconi et al., 2017).
Mid-life ageing in women is characterised by three stages: 1) early chronological (pre-menopause), 2) endocrinological (menopause) and 3) late chronological (post-menopause) (Scheyer et al., 2018; Mishra et al., 2022). Throughout these steps there is a shift in the energy metabolism of the brain. Unlike a young brain, it stops relying exclusively on glucose, and switches to utilising lipids and ketone bodies (Mishra et al., 2022). It is thought that this change in fuel dependence to be more lipid-based puts the greatest store of fatty acids in the CNS – white matter – at risk of breakdown in order to produce ketones. Data from numerous studies on Alzheimer’s Disease point to endocrinological ageing as the critical ‘tipping point’, which could initiate the start of late-onset AD (Scheyer et al., 2018).
You may ask: “How does it affect men, if the process is linked to endocrinological changes with menopause?”. Well, males with AD exhibit the same shifts in the brain’s energy metabolism, which lead to fuel deficits, immune system activation and progression of degenerative changes. The process shares pathological mechanisms in both sexes. However, in females the critical catalyst – decreased oestrogen control of glucose metabolism – in turn leads to increased risk of developing disease (Mishra et al., 2022).
It may seem a bit unfair, that a physiological hormonal transition predisposes women to developing such debilitating conditions as dementia. Despite the multiple dementia risk factors that women face as they near the menopause, there is hope in the brilliant scientists and doctors at the frontiers of dementia research. Moreover, evidence-based lifestyle advice is available to people, who want to decrease their risk of developing a neurodegenerative condition. Some of these practices include: preventing head trauma, limiting alcohol and smoking, managing neuropsychiatric disorders, and in some cases – managing menopause with Hormone Replacement Therapy – which tackles the key hormonal risk factor of dementia (Dementia prevention, intervention, and care: 2020 report of the Lancet Commission).
References:
Brinton RD, Yao J, Yin F, Mack WJ, Cadenas E. Perimenopause as a neurological transition state. Nat Rev Endocrinol. 2015 Jul;11(7):393-405. doi: 10.1038/nrendo.2015.82. Epub 2015 May 26. PMID: 26007613.
Lisa Mosconi, Valentina Berti, Crystal Quinn, Pauline McHugh, Gabriella Petrongolo, Isabella Varsavsky, Ricardo S. Osorio, AlbertoPupi, Shankar Vallabhajosula, Richard S. Isaacson, Mony J. de Leon, Roberta Diaz Brinton
Neurology Sep 2017, 89 (13) 1382-1390; DOI:10.1212/WNL.0000000000004425
Scheyer, O., Rahman, A., Hristov, H. et al. Female Sex and Alzheimer’s Risk: The Menopause Connection. J Prev Alzheimers Dis 5, 225–230 (2018). https://doi.org/10.14283/jpad.2018.34
Mielke MM, Vemuri P, Rocca WA. Clinical epidemiology of Alzheimer’s disease: assessing sex and gender differences. Clin Epidemiol. 2014 Jan 8;6:37-48. doi: 10.2147/CLEP.S37929. PMID: 24470773; PMCID: PMC3891487.
Aarti Mishraa, Yiwei Wanga, Fei Yin, Francesca Vitali, Kathleen E.Rodgers, Maira Sotoa, LisaMosconi, Tian Wang, Roberta D. Brinton, Person Envelope et al. (2021) A tale of two systems: Lessons learned from female mid-life aging with implications for alzheimer’s prevention & treatment, Ageing Research Reviews. Elsevier. Available at: https://www.sciencedirect.com/science/article/pii/S1568163721002890?via%3Dihub (Accessed: January 8, 2023).
Dementia prevention, intervention, and care: 2020 report of the Lancet Commission: Gill Livingston, Jonathan Huntley, Andrew Sommerlad, David Ames, Clive Ballard, Sube Banerjee, Carol Brayne, Alistair Burns, Jiska Cohen-Mansfield, Claudia Cooper, Sergi G Costafreda, Amit Dias, Nick Fox, Laura N Gitlin, Robert Howard, Helen C Kales, Mika Kivimäki, Eric B Larson, Adesola Ogunniyi, Vasiliki Orgeta, Karen Ritchie, Kenneth Rockwood, Elizabeth L Sampson, Quincy Samus, Lon S Schneider, Geir Selbæk, Linda Teri, Naaheed Mukadam










