Master of Physiotherapy,
University of Canberra
Dementia is currently Australia’s third leading cause of disability burden and is predicted to become the leading cause of disability by 2016 with an estimated threefold increase in people living with dementia to occur by 2050 (AIHW 2006; ABS 2008b). One factor which may contribute to this drastic change is an increase in sedentary overweight and obese individuals, with research suggesting that an increased body mass index (BMI) leads to an increased risk of dementia (Anstey et al 2011). One way to combat this risk is for health professionals and the general population to work together to maintain a recommended BMI through regular physical activity (Rolland et al 2007).
The term dementia describes a group of symptoms of a disease rather than a single disease entity. It encompasses a range of impairments each of which stem from an underlying brain dysfunction. It includes language, memory, perception, personality and cognitive skill impairments. Although the healthy brain does undergo neurological changes as we age, dementia itself is not a natural part of ageing even though the incidences increase notably with age (AIHW 2006). The chance of living with dementia doubles every five years after the age of 65 and by the age of 85 it affects 24 per cent of the population. This is a disconcerting figure, assuming the current dementia prevalence rates continue, considering Australia’s over 85 population has increased by 54 per cent between 2002 and 2012 and is expected to expand another 150 per cent by 2042 (AIHW 2006; ABS 2011-2013). What is even more alarming is that the current dementia prevalence rates may in fact exponentially increase not in line with the growing age in population but, alternatively, with the growing body weight in the population.
Australia’s overweight and obese population has steadily risen from its 1995 figures of 56.3 per cent to 63.4 per cent in 2011-2012 (ABS 2011-2012). The World Health Organisation (WHO) has referred to increasing trends as a “global epidemic of obesity” (Sorenson 2000). The causes for increases in BMI are complex with genetic and environmental risks contributing. The National Health and Nutrition Examination Survey (NHANES) I, II, III and 1999-2002 suggests as the human genetic makeup has not altered in the past 30 years, that environmental factors are most likely attributable. Environmental factors encompass a myriad of daily living determinants with dietary intake and physical activity having direct consequence. Dietary intake determinants in association with reduced energy expenditure lead to energy imbalances and, as such, a potential increase in BMI (Woodward-Lopez et al 2006). An increase in BMI beyond 25 kg/M2carries with it an increased risk for type 2 diabetes, cardiovascular disease (CVD), and other morbidities. In the past decade research has begun to also find a link between an increased BMI during mid- and late-life and an increased dementia risk.
An increase in BMI above that of 30kg/M2 increases the risk of cardiovascular changes such as hypertension, visceral adiposity, high triglycerides, low HDL and diabetes. Metabolic syndrome, which is an umbrella term for said cardiovascular changes has been linked with an increased risk of cognitive decline (Yaffe et al 2004; Yaffe et al 2007; Komulianen et al 2007). Although dementia incorporates a decline in cognition, these particular studies did not examine an association with dementia. However, individual components of metabolic disease have been shown to increase the risk of dementia. A prospective study on diabetes showed an increased association with the risk of Alzheimer’s disease and vascular dementia (Biessels et al 2006). Similarly, hypertension increases the likeliness of developing dementia especially in mid-life, as does dyslipidemia (Qui, Winbald & Fratiglioni, 2005; Reitz et al 2004). Aside from individual CVD changes, an increase in mid- and late-life obesity itself increases the risk of dementia (Fitzpatrick et al 2009; Gorospe & Dave 2007; Anstey et al 2011; Xu et al 2011; Rolland, Abellan van Kan & Vellas 2008). Although links have been established between age-related BMI increases and dementia risk, the exact BMI/age ratio is conflicting (Fitzpatrick et al 2009; Xu et al 2011; Knopman et al 2007; Luchsinger et al 2007; Atti et al 2008). A number of reasons may contribute to this; (1) BMI is not an accurate indicator for adiposity in the elderly (Janssen, Katzmarzyk & Ross 2004), (2) low BMI is used as a preclinical identifier for dementia (Johnson, Wilkins & Morris 2006; Buchman et al 2005), (3) not adjusting results for cofounders (Ott et al 1998; Kuusisto et al 1994). Irrespective of ratios, any factor that increases the risk of dementia and, more importantly, is manageable need be exploited.
In relation to an imbalanced energy intake versus expenditure equation, physiotherapist services can influence the energy expenditure portion of it. Physical activity affords an important role in weight loss (Anderson et al 2001; Katahn et al 1982; Okay et al 2009) and has shown to credit an equal contribution to weight loss compared with dietary adjustments (Ross et al 2004). In those with a BMI greater than 25 kg/M2 who are able to participate in approximately 210 minutes of moderate intensity exercise per week (30 minutes per day) a modest weight loss or weight gain prevention is observed (Houmard et al 2004; Slentz et al 2004). Alteration in exercise intensity to a moderate level significantly alters the metabolic syndrome score, has direct positive effects on diabetes risk-related variables and lowers triglycerides when compared with vigorous intensity exercise (Johnson et al 2007). Conversely, Albert and colleagues reported that strenuous physical activity was associated with less cognitive decline than moderate level.
Weight loss in obese individuals also restores the fatty oxidative capacity of skeletal muscle back towards that of healthy aged-matched subjects (Menshikova et al 2005; Kelley et al 1999; Slentz, Houmard & Kraus 2009). Regular progressive resistance training is another method that can be adopted by physiotherapists as a prescription alternative to afford increased muscle mass and weight loss in their clients (Aagaard et al 2010). Increases in muscle mass will not only further aid in fatty oxidation but will also combat other aged-related diseases such as osteoporosis and osteoarthritis (Messier et al 2004; Gass & Dawson-Hughes 2006; Di Monaco et al 2011). Physically active individuals have been shown to be less likely to develop dementia than aged-matched sedentary individuals (Laurin et al 2001; Rolland et al 2007).
Certain activities not only expend energy but also target better brain function with cognitive training and social interaction. Leisure activities containing physical, mental and social components have the most positive effect on dementia prevention (Rolland et al 2008; Fratiglioni & Wang 2007). Numerous studies have shown a positive correlation between physical activity and a decreased dementia risk. Participation in regular aerobic exercise maintains a portion of the loss of cognitive function that is normally observed with ageing (Pitkala et al 2013; Shay & Roth 1992; Weuve et al 2004). As little as a one-hour session three times per week over six months can increase brain volume (Colcombe et al 2006). Similarly, the Canadian Study of Health and Aging highlighted that regular physical activity compared with no activity lowered the risk of cognitive impairment and Alzheimer’s disease. A 2004 study by Abbott and colleagues showed that men who walked an average of 3.2 kilometres a day were 1.8 times less likely to develop dementia when compared to sedentary counterparts. Similarly, Larson et al demonstrated people who exercised three times or more per week had a risk of 13 per 1000 person-years compared with those who exercised fewer than three times per week who had a risk 19.7 per 1000 person-years. Activities included walking, cycling, water aerobics, weight training, stretching and swimming. Larson also highlighted that irrespective of exercise days physical functioning alone was associated with dementia, suggesting that altering the relationship between physical functioning and dementia through exercise may be a link to the underlying mechanisms, however further investigations are needed.
With an ageing population, in addition to an increasing overweight and obese population, emphasis need be placed on current resources available to aid in the prevention of dementia. The contributing factors to high body adiposity are multifactorial, as are the physical activities that combat it. This presents gaps in the research as to which specific factors provide the strongest results. However, the evidence for a reduction in BMI to healthy norms and an increase in physical activity to prevent dementia is encouraging. As health professionals, physiotherapists play an integral role in not only administering physical activity programs to the overweight populous, but also in educating them on the importance of maintaining a healthy BMI.
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