Diabetes, “Pre-diabetes”, Dementia and “Pre-Dementia”

The coming Tsunami of Care Needs for Seniors in the US

The burden of care for persons with Dementia falls mainly on the immediate family.  This burden, already significant is forecast to grow substantially over coming years, and developed countries will almost certainly face a huge problem due to the confluence of a number of factors.  The sheer growth in those expected to be diagnosed with dementia is daunting plus the at risk population – already large will also expand.

A recent review published in January 2019 documents the increase in dementia diagnoses from around 5 million in 2014 – representing around 1.6 % of the US population, to 5.8 million forecast in 2020.  This represents an average annual growth of around 2.7 %.  This is then expected to accelerate to grow at over 3 % per year with the numbers diagnosed with dementia in 2030 reaching 8.3 million and 11.1 million in 2040.  From there, growth rates are forecast to reduce, but even then an estimated 13.9 million will be diagnosed in 2060, representing over 3.3 % of the US population.

Even as we continue to find improved treatment and approaches to manage these public health challenges, the demographic trends also point to an expected increase in the proportion of those needing care to those able to provide it.  Families are increasingly less likely to stay within local communities, meaning that what was common in the past – ie. that spouses and children would provide the main care is becoming less and less the norm.  For people to remain living at home (by and large the wish of a substantial majority) families, friends and professional caregivers will be relied on to provide ever increasing levels of care and support.

The ageing of the population means that the dependency ratio (the proportion of those aged under 18 and over 65 to those in working age groups) will increase.  The population of under 18s will not grow as rapidly, however older age groups will become an ever increasing proportion of the population. Again reflecting an increased care burden on those aged 18 – 64, and also older persons whose spouses and other family members have health and other care needs.

From less than 17 % in 2020, the percent of the population aged over 65 in 2060 is forecast to be 23.5 %.  The over 85 age group – only 2% of the population in 2020, will be 4.7 % in 2060

The underlying causes of Dementia, including Alzheimer’s continues to be the focus of research and we can only hope that progress continues to be made.  Unfortunately we can see clear links with another major chronic disease – Diabetes.  This is thought to be due to several mechanisms, but primarily because of the effect of insulin resistance on brain structure and function, and also the increased risk of vascular disease with diabetes – leading to higher rates of stroke, heart disease (both of which are associated with cognitive decline), and vascular dementia (the second most common cause of dementia after Alzheimer’s).  The following figure provides an outline of the mechanisms which can lead from diabetes to a diagnosis of dementia.

Image on the right From Biessels et al.  Lancet Neurology 2006; 5: 64-74

Again the current prevalence and forecast increase in diabetes in the US represents a public health challenge of enormous magnitude.  Nearly 30 million Americans are expected to have a diagnosis of diabetes by 2020, and another 10 – 15 million undiagnosed. 

In addition, around 140 – 150 million will have "pre-diabetes" – impaired insulin sensitivity associated with diabetes risk factors – obesity, poor diet and lack of exercise.  Importantly, research continues to accumulate which shows that both diabetes and pre-diabetes are associated with an increased risk of dementia and cognitive impairment (so-called "pre-dementia").

Cognitive impairment in this sense is often not easily recognized – since there is generally little or no memory problems, but rather impairment in other functions, such as executive function.  This is the part of the brain associated with planning, decision making, judgement and behaviour.  An unrelated and much less common form of dementia – fronto-temporal dementia also affects executive function, but this is a different process.

The implications of executive dysfunction and cognitive impairment in people suffering from diabetes can be quite profound.  Consider that the objectives of health care in patients with diabetes are to minimise progression of the disease, and prevent complications.  The mechanisms by which this is achieved is to follow lifestyle guidelines for diet and exercise, adhere to medication regimes and to attend check-ups and therapy with health care providers.  All of these activities can be sub-optimal in someone with cognitive impairment and executive dysfunction.  For people living alone without family and friends to help support their health care, this can mean increased risk of an acute event – eg. stroke, or further gradual decline in their disease process, all of which leads to increased risk of dementia.

Putting all this into context – there is a huge challenge for the health care system and for policy makers.  Not only will there be a relentless and relatively rapid increase in demand for services, we must continually look at ways to try and halt or reverse these trends.  This is perhaps the major problem, since it has been well known for many decades what we should be doing, but putting this into practice appears beyond our scope at present.  We know for example, that type 2 diabetes can be controlled and even reversed by adopting a healthy diet and following guidelines for an active lifestyle.

Experts disagree about some of the details, and even some of the basics, but all would agree that the current Standard American Diet (appropriately referred to by its acronym SAD) which consists of a large proportion of processed food, high in refined carbohydrates, added sugar, fats and salt, and low in whole foods, combined with lack of regular exercise is the prime culprit.  We know also that lower socio-economic groups are at increased risk of heading down this pathway, and these are also the groups who can least afford health care now, and will be least able to afford the cost of home care and other support that goes with a diagnosis of dementia.  Those without family support face a bleak future.

While medications and treatment options continue to be developed, it is this fundamental lifestyle problem which is driving the increase in diabetes, and consequently dementia.  Options to promoting healthy food choices and lifestyles are attempted, but discouraging unhealthy eating by increasing taxes on sugar, processed and fast food seem to be off the agenda, despite many public health experts arguing for this for many years.  In which case we are heading inexorably to the grim scenario described above.

References

Bello-Chavolla et al  Pathophysiological mechanisms linking type 2 diabetes and dementia: Review of evidence from clinical, translational and epidemiological research.  Curr Diabetes Rev. 2019 Jan 15. doi: 10.2174/1573399815666190129155654. [Epub ahead of print]

Biessels et al.  Risk of dementia in diabetes mellitus: a systematic review
The Lancet Neurology  –  Volume 5, Issue 1, January 2006, Pages 64-74 https://doi.org/10.1016/S1474-4422(05)70284-2

Dybjer et al.   Pre-diabetes and diabetes are independently associated with adverse cognitive test results: a cross-sectional, population-based study BMC Endocr Disord. 2018; 18: 91.   Published online 2018 Dec 4. doi: 10.1186/s12902-018-0318-3

Jansen van Vuren et al.  Prospective associations between cardiac stress, glucose dysregulation and executive cognitive function in Black men: The Sympathetic activity and Ambulatory Blood Pressure in Africans study   First Published December 17, 2018 Research Article Diabetes & Vascular Disease Research 1-8 https://doi.org/10.1177/1479164118816221

Janssen et al.  HbA1c, Insulin Resistance, and β-Cell Function in Relation to Cognitive Function in Type 2 Diabetes: The CAROLINA Cognition Substudy. Diabetes Care. 2018 Nov 19. pii: dc180914. doi: 10.2337/dc18-0914. [Epub ahead of print]

Lin et al.  Projection of the future diabetes burden in the United States through 2060
Population Health Metrics 2018 16:9   https://doi.org/10.1186/s12963-018-0166-4

Vespa et al., Demographic Turning Points for the United States: Population Projections for 2020 to 2060 Current Population Reports, P25-1144, U.S. Census Bureau, Washington, DC, 2018.

Matthews et al.  Racial and ethnic estimates of Alzheimer’s disease and related dementias in the United States (2015–2060) in adults aged over 65 years    Alzheimer’s & Dementia 15 (2019) 17-24

Rowley et al.  Diabetes 2030: Insights from Yesterday, Today, and Future Trends.
Popul Health Manag. 2017 Feb;20(1):6-12. doi: 10.1089/pop.2015.0181. Epub 2016 Apr 28.