Can active socialization prevent dementia?

In the WHO guidelines and reports from authoritative journals such as The Lancet, it is mentioned that lack of social interaction is associated with an increased risk of dementia, and active social participation is also recommended as a preventive method for dementia, although the level of evidence is relatively insufficient , Mostly from small or short-term research

Earlier this year, "The Lancet Public Health" published a paper from the Oxford University team that proposed a 20-year prospective study of nearly a million women in the UK that challenged existing guidelines: Social inactivity is mainly the early manifestation of the gradual onset of dementia, rather than the cause of dementia

We know that the pathological process of dementia is often gradual, such as the abnormal deposition of amyloid and tau protein or the development of other brain diseases

In order to distinguish as much as possible whether the reduction of cognitive and social activities is the "cause" or "effect" of dementia, prospective studies with sufficient follow-up time are needed to more reliably analyze the short-term and long-term associations

This British study of millions of women began in 1996-2001

At the same time, based on the NHS electronic medical records, the research team collected the admission information of their first recorded dementia, and analyzed these cognition, social activities and subsequent dementia for 0-4 years, 5-9 years, and 10 years or more.

Ten years after the first report of activity information, only 1% of women were lost to follow-up, and nearly 800,000 people (93%) were still alive and had no medical records of dementia

The analysis found that after the first collection of activity participation information, only in the first ten years, non-participation in cognitive or social activities was associated with a higher risk of dementia; and in the second ten years, this association Almost disappeared

Looking at the different activities, the results are similar

Moreover, regardless of whether it was 50+, 60+, or 70+ when the activity information was first reported, this was true for women of different ages.

▲Compared to participating in various activities (dotted line), those who do not participate in the activities are at risk of getting dementia after 0-4 years, 5-9 years, and 10 years (based on the time of first admission to the hospital)

The vertical bar is the 99% confidence interval

However, it is worth noting that when adjusting the influence of other factors, the research team found that if only the age and residential area are adjusted, the factors that have the greatest influence on the relationship between participation in activities and future dementia are education and self-rated health

Reading information was collected later, but it also showed a similar trend.

▲Compared with participating in reading (dotted line), non-participating readers are at risk of dementia (calculated based on the time of first admission to the hospital) after 0-4 years, 5-9 years, and 10 years

The vertical bar is the 99% confidence interval

Therefore, the research team proposed that only by pulling the long time axis and looking back can we better understand the impact of life>
.
The results of this recent and longer-term irrelevant analysis suggest that before dementia is diagnosed, various mental and physical activities will gradually decrease due to the gradual onset of dementia, not because inactivity will lead to dementia in the future
.

Challenges from colleagues in the industry

After the publication of the paper, the interpretation of the data and the conclusions reached were challenged by Dr.
Robert P Friedland from the Department of Neurology at the University of Louisville in the United States
.
This set of discussions was published in "The Lancet-Public Health"
.

Dr.
Robert P Friedland believes that, on the one hand, there is a large amount of biological evidence supporting that cognitive and physical activities are beneficial to the brain, and participation in activities and short-term (within 10 years) dementia risk reduction are not only interpreted as "reverse causality.
" It may also be a direct cause and effect relationship
.
For example, in a retrospective case-control study with rigorous disease assessment and longer retrospective, about 72-year-old 193 Alzheimer’s disease patients and 358 control population were asked about their participation in 26 activities during their 20-60 years of age.
Circumstances, the results show that the risk of Alzheimer's disease is nearly three times higher for people with below-average activity levels
.

On the other hand, there are many studies showing that such activities are still valuable in preventing heart disease and high blood pressure
.
Therefore, this research is not enough to shake the current guidelines and recommendations of “participate more in cognitive social activities to prevent dementia”
.

Author team reply

In this regard, the author team also refuted and reiterated their views
.

First of all, as to why it is interpreted as "reverse causality", the author emphasizes that in the longer term, the bias of reverse causality will gradually shrink.
The comparison of data at different times supports the short-term association as "reverse causality
.
" The author team also added data on physical activity, showing similar trends with awareness and social activities
.
In the first ten years after reporting lack of physical activity, the onset of dementia was significantly excessive, and physical activity was no longer related to the onset of dementia after 10-20 years
.

▲In the study of millions of women in the UK, compared with participation in activities, non-participation in physical activity (blue line), cognitive or social activities (red line) is associated with the risk of dementia (picture source: reference [4])

The author team further pointed out that the evidence cited by Dr.
Robert P Friedland is a small study, and when it is clearly known that the subject has Alzheimer's disease, collecting information on past activities is prone to recall bias
.
In contrast, the British Million Women Study is forward-looking.
Its advantage is that it records activity information many years before the onset of illness, which can provide fair evidence of long-term effects; and, with the help of national databases, it almost completely records the study population’s Medical records for dementia and other diseases
.

Evaluation of review articles in the same period

A review article published in the same period of "The Lancet-Public Health" pointed out that it is particularly important to explore the possibility of reverse causality regarding the risk factors of dementia, because the degenerative process of Alzheimer's disease (the most common form of dementia) may be It started decades before the diagnosis of cognitive impairment
.
With its huge sample size and long-term follow-up data, the British Million Women Study provides a unique opportunity to solve this problem and contributes important evidence
.

The review article also pointed out that this study also has some limitations, such as self-reported activity participation information and dementia information based on hospitalization databases may be inaccurate
.
In the future, we need more and more research to analyze the causal relationship, correlation strength and time window of changeable risk factors and dementia from the perspective of life course
.

Reference

[1] Sarah Floud, et al.
, (2021).
Cognitive and social activities and long-term dementia risk: the prospective UK Million Women Study.
The Lancet Public Health, DOI: https://doi.
org/10.
1016/S2468 -2667(20)30284-X

[2] Geir Selbæk.
(2021).
Dementia risk: time matters.
The Lancet Public Health, DOI: https://doi.
org/10.
1016/S2468-2667(21)00010-4

[3] Robert P Friedland.
(2021).
Cognitive and social activities and long-term dementia risk.
The Lancet Public Health, DOI: https://doi.
org/10.
1016/S2468-2667(21)00071-2

[4] Sarah Floud, et al.
, (2021).
Cognitive and social activities and long-term dementia risk – Authors' reply.
The Lancet Public Health, DOI: https://doi.
org/10.
1016/S2468-2667( 21)00072-4