Type II Diabetes and dementia
Type II Diabetes is a well-known risk factor for dementia. But how does Type II Diabetes actually influence our risk for dementia? And can Type II Diabetes also influence our disease progression once we have dementia?
Let’s find out.
Diabetes
Diabetes is one of the most common chronic conditions, but we have to carefully distinguish the two main types of diabetes – Type I and Type II Diabetes. The main difference between the two types of diabetes is when they start. Type I Diabetes is commonly diagnosed in childhood as people with this type of diabetes have difficulties making the hormone insulin in the body from birth onwards. Insulin helps to regulate the sugar (glucose) levels in our blood, which need to be kept at a constant level – not too low or too high. We need constant glucose levels in our blood so that our cells can work the most efficient at any given time. This means that people with Type I Diabetes can have too low or too high blood sugar levels because they do not produce sufficient insulin to regulate this process.
Insulin regulation and its impact on blood sugar levels are also key for Type II Diabetes, however, most people develop Type II Diabetes only from middle age onwards and not in childhood (as in Type I Diabetes). The other key difference between Type I and Type II Diabetes is that for Type I people’s bodies cannot produce sufficient insulin but for Type II it is that the body initially produces sufficient insulin but then slows down the insulin production – mostly in middle age. The exact mechanisms of why this happens are still being investigated but there are certain risk factors which make us more likely that this happens and we develop Type II Diabetes. Age is the most obvious one, as we already know that most people with Type II Diabetes are middle-aged or older. But also whether our relatives have diabetes can increase our risk, most likely due to genetic factors. There is also good evidence that ethnicity plays a significant role in Type II Diabetes with people from South Asian heritage known to have the highest risk for Type II Diabetes – again the exact reasons for this are still being explored. Finally, other health conditions such as hypertension (high blood pressure) and obesity (being overweight) also play significant roles in the development of Type II Diabetes. Of course, we can have a combination of any of those risk factors, which further increases our risk for Type II Diabetes.
Having Type II Diabetes should not be taken lightly, since unregulated blood sugar levels can create enormous havoc in our bodies. In the worst cases, these changes can lead to devastating health complications leading to blindness, amputations or serious heart conditions. It is therefore paramount that we maintain good blood glucose control even if we have Type II Diabetes, as the health consequences can be significant. The good news is that existing medication allows keeping those blood glucose levels under control if we keep a close eye on our blood sugar levels. The other good news is that lifestyle factors can influence the severity of our Type II Diabetes, this means if we are changing some of our lifestyle factors we can actually reduce our severity of Type II Diabetes, or even get rid of it.
Lifestyle choices and diabetes
Lifestyle choices are all the rage in dementia prevention/risk reduction, with scientific data has shown time and again that our lifestyle choices can reduce our risk for dementia by up to 40%. It is a very similar story for Type II Diabetes with lifestyle choices making a significant impact on our risk for Type II Diabetes. This makes perfect sense since many risk factors for Type II Diabetes (obesity, hypertension) are closely linked to lifestyle choices. In particular, lack of physical activity and a poor diet can increase our risk for Type II Diabetes, since it is more likely that we will be obese or hypertensive when we move too little or eat the wrong food. It is therefore important that we are aware of these risks so we can make informed decisions as to our lifestyle choices. A good starting point is public health guidelines, of which most state that we should eat a balanced diet, with low amounts of highly processed food, salt, sugar and alcohol. But, I guess we all know that. What is often less known is how much physical activity makes a difference to our health. Not only does it burn more calories but helps our body fight off disease and regenerate itself. Most public health guidelines recommend, therefore, and do at least 150mins of moderate physical activity, or 75mins of vigorous physical activity, per week.
How does one know the difference between moderate and vigurous physical activity?
One way to do this is via measuring our heart rate with a heart rate monitor. Luckily, these days many of us have smartwatches, which usually have a heart rate monitor and, therefore, we can directly measure our level of physical activity. For heart rate, moderate physical activity is defined as being physically active while our rate is within 50-70% of our maximum heart rate. Our maximum heart rate is calculated by subtracting our age from 220 beats per minute. However, this is only an estimate and should be taken as such. Still, it highlights that our maximum heart rate is dependent on our age and the older we get, the lower our maximum heart rate is since we subtract a larger number from 220. It also means that our moderate physical activity heart rate zones (50-70% of our maximum heart rate), change with age. For example, somebody at 50 will have a moderate physical activity heart rate zone of 85 – 119 beats of per minute (220-50 = 170 maximum heart rate; 50% of 170 = 85; 70% of 170 = 119). While someone at 75 will have a moderate physical activity heart rate zone of 73 – 102 beats of per minute (220-75 = 145 maximum heart rate; 50% of 145 = 72.5; 70% of 145 = 101.5). So, if you target those heart rate zone and measure the time you spent in them you will know exactly whether you do sufficient moderate physical activity – vigorous physical activity of course just exceeds the heart rate zones of moderate activity. Luckily most smartwatches calculate that all for us and even give us a neat breakdown of moderate and vigorous physical activity.
But if this is all too much ‘faff’ for you then there is a much simpler way to estimate whether you are doing moderate or vigorous activity or neither. It is based on whether you can talk or sing while doing the activity. Most activities that are below the moderate activity level allow us to talk but also sing. Just imagine having a lovely stroll around the countryside. Maybe you would not actually burst into a song doing this – it seems only people in musicals do this. But you could sing if you wanted. However, once you enter the moderate physical activity heart rate zone it will be very hard for you to sing, while you might be still able to hold a conversation with a friend. Just imagine a scenario of brisk walking which allows you to talk but definitely not sing along, without puffing like a steam engine. Finally, vigorous activity does not usually allow us to even talk anymore to someone while doing the activity. Just imagine going for a run with a friend. You might say the odd word or short sentence but it would be difficult to have a coherent, in-depth conversation with that friend. In summary, sing & talk = neither moderate nor vigorous physical activity; talk but not sing = moderate physical activity; and no singing or talking =vigurous physical activity. Just keep in mind that this is an estimate, but allows a quick and simple estimate of our physical activity levels.
Is all this worth it, you might righlty ask?
The short answer is, definitely! Physical activity, in particular, has been shown to reduce the risk of Type II Diabetes dramatically and many people will even go in remission from Type II Diabetes once they become more physically active. It means that some people might ‘cure themselves’ from Type II Diabetes, simply by being more physically active. How amazing is that! And it even doesn’t cost us anything, except for time and commitment… and maybe a new sports outfit. However, if we have not been physically active for a long time, we should always first consult our doctor or nurse to discuss whether our health allows us to become more physically active… and also take it easy at the beginning. The worst thing to happen would be that we injure ourselves immediately when we start being more physically active, which would lead us to be even less physically active. In sports science, a ‘rule of thumb’ is never to increase physical activity by more than 10% during each step. This even applies to professional sportspeople. So, if we are starting from a very low level of physical activity, we should be starting very slowly. The benefits will come in the long term, so there is no need to rush. Let’s just get moving and more importantly keep moving, but maybe not singing at the same time.
What has that all to do with dementia?
Type II diabetes and dementia risk
There has been over the years an increasing recognition that Type II Diabetes increases our risk for dementia significantly. Most scientists first thought that it was simply a collateral effect since Type II Diabetes also occurs due to other health conditions, such as obesity and hypertension which are also risk factors for dementia. But it soon emerged that there were far more direct links between Type II Diabetes and dementia. The realisation emerges when evidence was showing that insulin misregulation in Type II Diabetes not only affects our body but quite specific aspects of our brain health.
Which aspects of brain health are affected by Type II Diabetes?
The key is to understand that insulin is very important for our brain health. Let’s remember that insulin is a key hormone in the development of Type II Diabetes, as it allows regulation of our blood sugar levels in our blood. One important thing to realise that the regulation of our blood sugar levels for our whole body is conducted from our brain or more specifically one brain region – the hypothalamus. The hypothalamus is a key brain region for the interaction of our nervous system with our hormonal system. For example, the hypothalamus regulates many of our sexual functions, via regulating oestrogen, progesterone and testosterone – our main sex hormones. Similarly, the hypothalamus is very important for our blood sugar and satiety regulation. Insulin is key to that as we already know and it should come therefore not as a surprise that one of the highest concentrations of insulin in the brain can be found in the hypothalamus.
But insulin has many other functions in the brain and can be found in many other brain areas. One critical function it has is to support the blood brain barrier. The blood brain barrier is, as the name gives away a barrier separating the brain from the blood supply. In essence, the brain needs to be protected from potential pathogens in the blood which can create havoc in the brain. Insulin is key in the maintenance of the blood brain barrier and therefore changes to insulin levels can affect the health of blood brain Barrier and make the barrier potentially more ‘leaky’ by letting pathogens through. The other functions of insulin are mostly related to being neuroprotective, which means that it helps to protect nerve cells or even helps to regenerate nerve cells when they get damaged. We can see now that insulin has some vital functions for our brain health. But one crucial aspect for dementia we have not yet mentioned for insulin.
The final aspect is that insulin is also directly involved in the build-up of proteins responsible for dementia. For example, insulin is critical for some steps of the removal of beta-amyloid. If beta-amyloid accumulates over time, it can increase our risk for dementia and hence keeping beta-amyloid levels low is an important aspect to reduce our risk for dementia. Further, insulin is directly involved in the phosphorylation of tau. Tau is the other critical protein, which if it accumulates can lead to Alzheimer’s disease in particular. The phosphorylation of tau is a key aspect in the accumulation of tau. Phosphorylation means that the molecule phosphate attaches itself to tau – insulin plays a role within this phosphorylation process. For yet unknown reasons when too much phosphate attaches to tau (it becomes hyperphosphorylated), it cannot function anymore properly and starts accumulating, increasing our risk for dementia. There are many investigations underway as to how insulin potentially affects this process and directly influences our risk for dementia. Regardless, it should become clear now that once we have Type II Diabetes, our insulin regulation becomes impaired and this can also affect our brain health. More importantly, it can directly affect our risk of developing dementia in the future.
So, does that mean that we are at greater risk of dementia if we have Type II Diabetes?
Yes and no. Yes, since we know that insulin misregulation can increase our risk for dementia. However, the research evidence has also shown that if people with Type II Diabetes regulate their blood sugar/insulin levels well, via medication and/or lifestyle, they do not show an increased risk for dementia. Instead, it is people who have either ‘undiagnosed’ Type II Diabetes, meaning we have Type II Diabetes but not aware of it, or who have poorly regulated blood sugar/insulin levels that are at the highest risk for dementia in the future. It is, therefore, worth getting regularly checked for Type II Diabetes from middle age onwards and if we have the condition to make sure that our blood sugar/insulin levels are well regulated with medication and/or lifestyle choices.
How about the impact of Type II Diabetes when we have dementia?
Type II Diabetes during dementia
This is an important topic, which has been not as much investigated, despite its importance. However, similarly to the risk reduction before we have dementia, Type II Diabetes can impact our dementia progression when we have dementia. The problems become more about regulating blood sugar/insulin levels once we develop cognitive and memory problems, as we might forget to take our medication or we cannot be anymore as physically active. This can clearly affect our insulin levels and dementia progression.
The other critical event is when we have dementia and develop hypoglycaemia – too little sugar in our blood. Hypoglycaemia can lead us to have short ‘blackouts’ as our brain does not have sufficient sugar to function anymore properly. Such blackouts are in general not harmful, however, they can lead to falls which can have significant consequences when we age. When we age our bones are not as strong anymore, which means that we are at a higher risk of having fractures when falling. Indeed, one of the most common hospital admission reasons for older people are fractures caused by falls – in particular hip fractures. These fractures lead to long hospital stays and often also subsequent care home placements as people do not regain their full functional mobility to before and hence will struggle to live again in their own home. Falls are therefore a critical event to avoid when ageing as they can have significant consequences for our life.
This is particularly true for hypoglycemic events, which lead so often to falls and subsequent fractures. Monitoring blood sugar and insulin levels emerges therefore as a critical aspect for avoiding falls. Luckily these days devices allow us to measure our blood glucose continuously and send warnings either to a device or a mobile phone when our blood sugar levels are too low or too high – either not being good for us. This new technology will hopefully make further inroads in the next years to avoid hypoglycemic events and subsequent falls. Regardless, monitoring of blood sugar levels remains very important even when we have dementia.
Summary
In summary, Type II Diabetes is a serious, long term condition, which not only affects our body but also our brain health. Type II Diabetes has similar risk factors as dementia but can also increase our risk of dementia directly. Specifically, changes to insulin levels in the brain affect our blood brain barrier and the regeneration of our nerve cells. But it also affects directly the accumulation of proteins, such as amyloid and tau, which are important in the development of dementia. However, it is people who have undiagnosed or poor regulated Type II Diabetes who are at the highest risk for dementia, since their blood sugar/insulin levels are not as well controlled by medication or lifestyle choices. Type II Diabetes also can have a significant impact on when we have dementia, as we might forget our medication leading to poorer blood sugar/insulin regulation and hence potentially faster disease progression. Finally, hypoglycaemia events are to avoid at all costs, since they can lead to falls, fractures and hospitalisation, further reducing the independence of the person with dementia and potentially accelerating their disease progression.
Links
- https://www.diabetes.org.uk/type-2-diabetes
- https://www.alzheimers.org.uk/categories/risk-factors/diabetes
- https://www.mayoclinic.org/diabetes-and-alzheimers/art-20046987
