Issue: January 2019 | Disability, Life | Dr. Chris Ball
There has been a
significant change in thinking about the problems posed by dementia (chronic
progressive neurodegeneration causing decline in cognitive function) by both
researchers and the wider health promotion community over the last few years.
In the early 1990s
although knowledge of dementia risk factors was emerging, it was concluded that
there was no justification to conduct trials or introduce large-scale
interventions to prevent the illness.1 Over the following
20 years, the focus was primarily on developing treatments for the
pathological brain functions identified as the cause of cognitive decline. In
part this was because the risk factors identified, old age, genetics and head
injury, were not felt to be amenable to change, but it was also because the
drive to develop pharmacological treatments, based on the cholinergic and
amyloid hypotheses, was very strong.
The failure of these
paradigms to deliver meaningful treatments and the recognition that the
incidence of dementia has been declining in certain communities led to
rethinking the approach, with a move away from treatment towards prevention.2 The
discovery that biomarkers of disease show changes many years prior to the
development of clinically significant symptoms suggested that interventions
must be made much earlier if the disease is to be treated or, more importantly,
prevented.
The scale of the
problems associated with an aging population, the development of dementia and
provision of care are well known; currently 850,000 people in the UK and
47.5 million worldwide live with dementia. These figures could rise to
2 million and 150 million respectively by 2050.3The
numbers translate not only into significant direct and indirect care costs
(higher than the costs of cancer, heart disease or stroke) but also very
considerable individual suffering. In the absence of effective treatments even
relatively small reductions in the incidence of the disorder or delaying the
onset of clinical symptoms would reap significant benefits.
It has been difficult to
develop a “return on investment (ROI)” tool to quantify the financial
effectiveness of interventions as few studies are analysed in this way. The
evidence can be difficult to interpret because studies often include both
younger and older people, use cognitive change rather than developing dementia
as their outcome measure, or have not been in place for long enough to
understand their full implications.4 Despite these caveats it
has been argued that by implementing “best-practice” interventions to reduce
risk factors the UK could save £42.9 billion by 2040 (minus the cost of
the interventions).5 However the data is interpreted there is a
broad consensus that about one third of dementia cases might be attributable to
“potentially modifiable” risk factors. A 20% reduction in these risk factors
per decade would reduce the UK prevalence by 300,000 (16.2%) cases by
2050.6 There have been a number of reviews published in recent
years, each offering a differently nuanced take on the issue. Whilst more
reviews should not be equated with more evidence, it is an indication that
prevention is seen as increasingly important and achievable. More recently the
UK government has recommended that advice about dementia prevention should be
included in the routine over 40s health check.7
Taking a lifestage
approach means considering interventions when it is unlikely that many people
would be thinking about developing dementia. Providing education beyond primary
school level is probably the most powerful intervention globally. Fewer years
of education is associated with a Relative Risk (RR) of developing
dementia of 1.59 (95% CI 1.26–2.01). Because worldwide the estimated prevalence
of poor education is so high (40%) this leads to a high Population Attributable
Fraction (PAF) for dementia.8 However, this discussion
will concentrate on mid-life interventions that have the potential to be
promoted through insurance channels.
Cardiovascular Health
Several reviews have
identified a series of risk factors focusing upon the cardiovascular health
(see Table 1).9
The widespread
introduction of programmes to reduce heart attack and stroke by ensuing good
cardiovascular health in mid-life (age 40-64) are probably responsible for
the reductions seen in the incidence of dementia (“What’s good for the heart is
good for brain”) in some markets.10Changes in vascular risk have
been implicated not only in Vascular Dementia (VaD) but also Alzheimer’s
Disease (AD). In clinical practice many patients who undergo scanning have
evidence of changes consistent with both of these common forms and are
classified as having Mixed Dementia (see Figure 1).
Although each of these
factors has a relatively small PAF (possibly in part due to the relative
success of these programmes) the potential combined impact remains large and
generates added impetus to the programmes.11 The impact of the
growing numbers of obese people will have on dementia incidence remains to be
seen as, in older age, obesity appears to have a mildly protective effects
against the development of dementia.14
The second group
identified for potential interventions are intimately involved with “lifestyle”
where there may be more scope for intervention (see Table 2).
Physical inactivity is
highly prevalent in many societies. Only 39.2% of German adults reach
recommended levels of physical activity. More concerning in this context is
that only 27.5% of adolescents attained the levels.16 There is
evidence that mid-life inactivity increases the risk of developing dementia and
that engaging with physical activity during mid-life is protective against
developing the disease. This makes it an attractive target for intervention
although the evidence suggests it is difficult to get over 50s to improve their
physical activity in a sustained manner.17
Some early work argued
that smoking might actually be protective against the development of AD but the
situation has subsequently become much clearer. Current smoking increases the
risk of all causes of dementia whilst smoking in the past does not increase the
risk. With 20% of the UK population continuing to smoke, the PAF is high
meaning significant reductions in dementia could be achieved. What is not yet
clear is when and for how long people need to be cigarette-free to reduce their
dementia risk in old age (see Figure 2).
There is some debate
about the importance of alcohol as a risk factor for dementia.19 Handing
et al. (2015) calculated a J-shaped curve for the risk of dementia in
relation to mid-life consumption over a 43 year follow-up (see
Figure 3)20, a finding broadly supported in meta-analytical
studies.21 This has meant that alcohol was not considered as a
significant risk factor in some analyses and the advice to reduce intake was
rather muted.22
This approach does not
do justice to the harms identified by Schwarzinger et al. (2018) who
reported that 57% of those developing early-onset dementia also had alcohol use
disorders.23 It is likely this group had co-morbidities that
might also predispose them to developing dementia.24Arguing that
your next glass of wine is going to help prevent dementia will not be very
persuasive.
The effects of diet in
mid-life on the development of dementia are much debated. Read et al.
(2017) concluded that the evidence is sparse because the majority of studies
concentrate on immediate health benefits rather than long-term outcomes.25 However
the “promoting brain health” team concluded that regular vegetable consumption
and a Mediterranean diet may protect against dementia, particularly AD. The
evidence for the benefits of vegetables is more convincing than it is for
fruit.26 A better diet probably works by developing
cardiovascular health and a healthy weight. The size of the impact of changing
diet is not clear although it clearly has a relationship with obesity and
diabetes.
There is an association
between mid-life mental activities and lower risk of dementia in later life
much of which is explained by early education and developing a cognitive
reserve. Even for those with less education working with more complex data has
the potential to reduce the risk. Although the studies are inconsistent in
their methodology and outcomes there is enough evidence to give some support to
the “use it or lose it” rubric.
Other potential
interventions
The association between
dementia and depression has been well described and is probably strongest for
those who experience late-life depression.27 For some, it is a
clear prodrome to the onset of cognitive impairment. For those who experience
mid-life depression alone, the risk of developing dementia increased by about
20%.28 It is not known if active treatment would have any
impact on the risk. More broadly described mental distress has been identified
as a potential risk factor but the evidence is relatively weak, particularly as
there is likely to be an overlap with depression, and the impact of programmes
to reduce stress have not been reported.29
As with other
“well-being” measures the associations between social isolation and loneliness
and dementia are more robust in old age than in mid-life. Common sense suggests
that a life-long pattern of active engagement outside the home would be likely
to persist into older adulthood where the impact might be felt but the evidence
that problems in mid-life are predictive of developing dementia is not robust.30
The concern about
repeated head injuries in collision sports is a reflection of growing awareness
of the cumulative damage repeated concussions may cause. Looking at broadly defined
head injury the pooled relative risk (RR) estimates showed that head
injury significantly increased the risks of any dementia (RR = 1.63, 95%
CI 1.34–1.99).31 The long term impact of implementing
standardised concussion assessment protocols such as the SCAT3 is not known but
can only be positive.32
Issues such as quality
of sleep and air experienced in mid-life may have an impact on developing
dementia in late-life but like many of the other potentially modifiable risk
factors evidence is not good but the arguments for generally improving health
through interventions is strong for both short and long term benefits.
Conclusions
Dementia, in all its
myriad forms, has no treatment that is effective once clinical evidence of the
syndrome has emerged. This does not mean that significant steps cannot be taken
to improve the quality of life of those living with the illness and their
carers. Medical interventions at the pre-clinical phase may be on the horizon
but interventions made in early and mid-life can happen today and significantly
reduced the risk of developing dementia.
The insurance industry
has engaged heavily in changing its relationship with their customers in recent
years, developing relationships through rewarding healthy behaviours and
providing well-being interventions well beyond their traditional remit. To date
the importance of interventions to preventing dementia have not been stressed,
partly perhaps because the people who might benefit from these interventions
are not necessarily considering the consequences of their behaviours into very
old age. However, as more people become concerned about this issue, and
products develop to reflect the risks of longevity (long-term care riders to
whole of life policies for example), the opportunity for insurers to play a
role in dementia prevention becomes a reality. Although many companies are
providing well-being services to their workers, the fluidity of the employment
market allows insurance firms to provide continuity in this area.
In order to prevent
dementia it is likely that a multipronged approach will be required and no
single intervention will be adequate. The engagement of insurers with their
clients as they develop their families and careers offers a unique opportunity
to intervene positively to reduce the suffering from dementia in years to come.
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