( Directly sourced from http://cerebralassessmentsystems.com/white-papers/white-papers-physicians/ )

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Prevalence of Dementia

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Alzheimer’s disease (AD) is the most common form of dementia, accounting for over half of dementia
diagnoses. As of 2015, an estimated 5.3 million Americans have Alzheimer’s and other dementias.
(Gaugler, 2015). This is an increase from 4.2 million in 2000, and it is estimated that it will increase even
more drastically to 13.2 million in 2050 (Hebert, 2003). Of those with LLCD, a large majority (82%) are age
75 or older. 

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It has been suggested that prevalence increases exponentially with age, doubling with every 5.5
year increment in age for North America, Latin America, and Asia Pacific (Prince, 2013). The Aging,
Demographics and Memory Study (ADAMS) used a sample of 856 individuals age 70 or older from
all regions of the country in a population-based study of dementia (Langa, 2005). They found that the
prevalence of dementia for adults aged 71 and older was 13.9%, and increased with age (Plassman,
2007).
Combining prevalence data with the estimated numbers of our growing elderly population has provided
estimates of the future prevalence of LLCD. In 2010, there were 4.7 million individuals in the United States
with AD. By 2050, this is expected to nearly triple to 13.8 million (Figure 5).
Worldwide, the number jumps to 115.4 million people with dementia in 2050, up from 35.6 million in
2010 (Prince, 2013). It is believed that by the middle of the century, 1 in 45 people will be diagnosed with
LLCD (Brookmeyer, 1998).
Prevalence of dementia among assisted living residents is even higher. Using national data, it has been
estimated that seven out of ten residents in these residences have some form of LLCD, with 19% of
residents having a severe impairment (Zimmerman, 2014). This is an 8% increase in prevalence from
a 2002 study that stated prevalence in assisted living facilities as being 62% (Matthews, 2002). This
increase poses a problem for institutions, a majority of which are not equipped to handle large numbers of
highly impaired patients.

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Incidence of Dementia

In 1998, the number of new diagnoses of AD and other dementias was approximately 360,000
(Brookmeyer, 1998). Another study used US census data and found the number to be 377,000 in 1995,
and estimated to grow to 959,000 in 2050, more than doubling (Hebert, 2001).
As with prevalence, the incidence of LLCD increases exponentially with age. In 2015, there will be
approximately 59,000 new cases among people age 65 to 74, 172,000 new cases among people age 75
to 84, and 238,000 new cases among the oldest-old, people age 85 and older

It has been suggested the current positive trend of medical, lifestyle, demographics, and social factors
have been positive for the physical and cognitive health of older Americans. With adults entering into old
age healthier and happier, one would assume that the incidence rate would drop in the coming years,
and may have already started to do so. In a large nationally representative survey of older Americans,
the prevalence of cognitive impairment and dementia decreased from 12.2% to 8.7% between 1993 and
2002 (Rocca, 2011). Despite the apparent falling rate of cognitive impairment, rates of incidence are
expected to skyrocket along with the growing older population.

Demographic Distribution of Dementia

There have been multiple studies investigating the demographic distribution of Alzheimer’s disease and
dementia. The most commonly found difference has been between men and women: on average, two out
of every three Americans with Alzheimer’s are women (Gaugler, 2015). This has not been attributed to
a sex difference in the prevalence of different dementia types (Fratiglioni, 1991). Rather, the difference
can be explained by the greater longevity of women compared to men (Figure 8). By age 70, there are
approximately 1.5 women alive for every man. By age 90, there are three women for each man (Katz,
2013).
There are racial and ethnic differences in the prevalence and incidence of Alzheimer’s Disease and other
dementias, though results have varied among different studies. Using a fixed cohort study, Whitmer found
that incidence densities were highest among African Americans and Mixed races (23/1,000 person-years),
and Native-Americans (21/1,000 person-years), and lowest among Asians (13/1,000 person-years). Risk
was intermediate for non-Hispanic whites and Latinos (Whitmer, 2014).

Although there are more non-Hispanic whites currently living with dementia than people of any other
racial or ethnic group in the United States, older African Americans are twice as likely to have Alzheimer’s
and dementia than Caucasians and Hispanics are about one and a half times as likely to have it as
Caucasians (Gaugler, 2015). These differences have been attributed to variations in lifestyle, health,
and socioeconomic risk factors, such as higher prevalences of diabetes and high blood pressure, lower
education, and a higher prevalence of alcoholic and unspecified types of dementias (Fratiglioni, 1991).
There is also evidence that among older African Americans and Hispanics there are more missed and
incorrect diagnoses of LLCD than compared to older whites. This could potentially be connected to findings
that the Mini-Mental Status Exam (MMSE), a brief test commonly used by physicians to screen for cognitive
deficits, may have low specificity within minority populations. Whites had only a 6% false-positive rate for
cognitive impairment with the MMSE, while African Americans had up to a 42% false-positive rate (Chin,
2011). Another impediment for the timely diagnosis of Alzheimer’s disease in minority populations could
be a lack of physical contact (Clark, 2005).
The epidemiology of dementia has long been studied and debated, and there is no doubt that the
exponential increase in new cases is a cause for worldwide concern. Though comparing studies from
different countries can be difficult, there is evidence that the prevalence of dementia is significantly
lower for developing countries than for developed countries. Estimates vary between countries, but a
systematic review calculated the overall prevalence of AD in developing countries to be 3.4 % (Qiu, 2009).
Comparatively, the prevalence of AD has been estimated at 6.9% in North America, 7.2% in Western
Europe, and 7% in Southern Latin America (see figure 9) (Prince, 2013).

 

Though the prevalence of dementia may be lower in developing countries, 58% of all people with dementia
in 2010 lived in countries with low or middle incomes. This proportion is expected to rise to 63% by 2030
and 71% in 2050. This is due to the rapid growth in the number of people over the age of 60 in these less
developed countries. By 2050, the number of people aged 60 years will account for 22% of the world’s
population, with 79% living in the world’s less developed regions (Prince, 2013).

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Conclusion
With future progressions of Alzheimer’s disease and dementia on an exponential rise, early detection of
the cognitive impairment will be the best defense against the tide that is threatening to crush the healthcare
the system in America and worldwide.