As the hottest summer on record comes to an end, many of us will have felt the benefits of the sun on our health. Longer days mean more exposure to Vitamin D, warmer temperatures often mean we are more likely to exercise, and we spend more time together socialising than we do in the winter. All of this adds up to an improvement in both physical and mental wellbeing.
But research published this month highlighted just how much the seasons can impact our cognitive ability and in particular, it revealed how, for those suffering with dementia, the impact can be even more acute.
The study, published in PLOS medicine, involved more than 3000 people across the United States, Canada and France and examined cognitive function across different seasons. It found that people with dementia were more cognitively alert in summer and autumn and, crucially, mental function declined by the equivalent of 4.8 years in the spring and winter months.
These findings are consistent with our understanding of how seasons impact other mental health disorders such as bipolar disorder, when sufferers tend to have mood abnormalities emerging in spring and summer.
Whilst on first look, these findings may be concerning, they highlight the opportunity to make significant changes to how we diagnose and treat dementia and give hope to scientists looking at preventative approaches to tackling the disease.
We know that millions of people who have dementia globally experience worsening cognitive function during winter, when they often become unwell and require hospitalisation. The conventional wisdom has been that this has always been caused by cold weather and infectious diseases.
But what if this was not the case? And what if we could prevent these people declining to the point at which they need hospitalisation.
The research found a 30 per cent increase in the likelihood of a person reaching the threshold for dementia diagnosis during winter months. This is a significant variation and provides ample evidence for us to consider taking a different approach to diagnosing cognitive decline.
The study authors recommended that more diagnoses should take place at winter-time, as this is when the symptoms are more evident. And these findings may also have significant implications for healthcare systems such as the NHS, which struggle with seasonal winter demand – much of this related to dementia.
If we were to measure brain function in the winter months, it would increase the chances of us identifying problems sooner. We know that early diagnosis of dementia is beneficial for a number of reasons – not only does it give patients and families time to prepare for the future and plan ahead but it also enables us to start making lifestyle changes which might prevent the symptoms getting worse.
Whilst the PLOS study does not explain why the seasons affect cognitive ability, it could shed light on how seasonal variation related to light exposure, vitamin D supplementation and other hormonal changes, as well as the secondary effects of increased social activities during the summer months can impact upon brain function.
Healthy habits have been proven to have a positive effect on slowing the progress of dementia, and many of these could be linked to variations in lifestyle throughout the seasons. For example, in the UK, around 1 in 5 people have low Vitamin D levels. We need to maximise light exposure in the mornings, for at least 20 minutes when we wake up but for people who are housebound, such as the frail and elderly, it is often much harder to be exposed to enough sunlight. In these cases vitamin D will need to come from other sources such as food or supplements.
Movement is also key. I have often spoken about the importance of daily physical exercise, but this often falls to the wayside in the winter months, when it is cold or difficult to get outside. However, one study showed that just 20 minutes of movement can facilitate information processing and memory function, which goes to show that exercise is just as important for our brain as it is for our bodies.
The same goes for socialising, diet and sleep. Inconsistent approaches to these vital lifestyle factors could be having a direct impact on the cognitive function of those suffering from dementia. So no matter what the season, we should be maintaining healthy habits that improve brain health and boost cognitive ability.
Dr Jamie Wilson is a dementia specialist and founder of hometouch, set up to improve the quality of home care and safeguard brain health