Understanding the Risk Factors of Dementia

Dementia is a significant health concern. Currently, 55 million people around the world are living with this condition. This number is expected to grow to 78 million by 2030 and reach 139 million by 2050. The global cost of caring for people with dementia was around $263 billion in 2019. By 2050, this cost could rise to more than $1.5 trillion. This situation makes it important for countries to focus on ways to reduce the number of dementia cases and the costs associated with it.

#Preventable Cases of Dementia

Research suggests that about 40% of dementia cases could be prevented with the right actions. The Lancet Commission highlighted several risk factors that people can change to help lower their chances of developing dementia. These factors include:

• Hearing Loss
• Lack of physical activity
• Feeling socially isolated
• Suffering from traumatic brain injuries
• Exposure to air pollution

While researchers have looked at these factors individually, they haven’t often studied them together across different countries.

#The Need for More Research

To help lower the number of dementia cases and their related costs, it’s essential to identify which risk factors lead to cognitive decline. These factors must be ones that people can change through their actions. If these factors truly impact cognition, there should be a clear connection between them and cognitive performance. Also, this relationship should hold true across different ages, cultures, and countries.

Our study aims to examine how these risk factors consistently relate to Cognitive Function across various countries. Instead of trying to prove that these relationships are causal (i.e., that one directly causes the other), we start from the opposite angle. If these relationships are causal, they should still be strong and identifiable despite other influencing factors.

Differences in culture, policies, economies, and other shared experiences across countries can lead to variations in how dementia arises and how risk factors play a role. As we will show, many of these modifiable risk factors do not consistently relate to cognitive performance, especially when we consider other factors that might also play a role. For factors with inconsistent relationships, it’s possible that they indicate other problems or that they are symptoms of dementia rather than true modifiable risk factors.

#The Study

To study these relationships, we used data from several aging studies that are comparable internationally. These studies include participants from the United States, Europe, and England. We focused primarily on seven specific risk factors, leaving out others due to a lack of consistent data across surveys.

To assess cognitive function, we used memory tests where participants had to recall a list of 10 words. Memory is an important sign of dementia, and longer word recall tests have historically been useful in predicting dementia and cognitive decline.

#Reviewing Past Research

We briefly looked at previous studies on how each risk factor might affect cognition and some challenges researchers face in proving these effects.

#Education

Higher levels of education are linked to a lower risk of dementia. The cognitive reserve theory suggests that people with more education may be better able to delay the mental decline associated with aging. However, more research is needed to uncover the exact reasons behind this. Socioeconomic status is one factor in this relationship, as higher education often leads to better socioeconomic conditions.

#Hearing Loss

Hearing loss, especially as people age, is associated with a greater risk of dementia. Two leading theories explain this. The sensory deprivation theory suggests that less sensory input can lead to isolation and changes in the brain that are connected with dementia. The cognitive load theory argues that when people struggle to process sounds, it diverts resources away from critical thinking. More studies are needed on how using hearing aids may affect dementia risk.

#Diabetes

Both types of diabetes can heighten the risk of dementia, with younger individuals at a higher risk. Several pathways explain this, such as increased chances of heart disease and inflammation. Healthy diets and exercise can help manage diabetes and may slow cognitive decline.

#High Blood Pressure

Research shows that high blood pressure can lead to vascular dementia through issues with blood flow in the brain. This link is particularly strong in middle-aged individuals. However, high blood pressure diagnosed in older age doesn’t seem to have the same connection to dementia.

#Obesity

Being overweight in mid-life is linked to a higher risk of dementia, potentially due to blood circulation issues and inflammation. Interestingly, being overweight later in life might be protective against dementia, although research is ongoing on this topic.

#Smoking

Current smokers seem to have higher chances of developing dementia compared to non-smokers. Possible explanations for this include increased inflammation and blood vessel problems. When studying the effects of smoking on dementia, it’s essential to consider factors that might protect long-term smokers.

#Depression

Depression, whether current or recent, increases the likelihood of developing dementia. It can contribute to issues like inflammation and reduced blood flow to the brain. However, it’s unclear if depression might be an early sign of dementia rather than a cause.

#Inconsistencies in Findings

Our analysis reveals that while some risk factors often show a consistent relationship with cognitive function (like education, hearing loss, and depression), others do not. For instance, the expected relationships between diabetes, hypertension, obesity, and smoking and cognitive function are inconsistent across different countries.

#Analyzing Data

We used data from national samples of people aged 50 and older. All three studies we examined follow the same participants over time and ask a range of questions about health and cognition. We focused on the initial interviews of participants, as repeated questioning can lead to better recall over time.

Our measure of cognitive function comes from summing the words recalled by participants on immediate and delayed tests. Risk factors are reported by participants and include information on their education, hearing ability, health conditions like diabetes and hypertension, and mental health.

#Results

We found a clear positive connection between education and cognitive function. More years of education were associated with better memory performance in all studied countries. However, the relationship between high blood pressure and cognition seemed inconsistent. While it initially appeared negative, accounting for other factors showed no significant relationship on average.

Interestingly, current smoking had unexpected results, as many countries showed a positive relationship between smoking and cognitive function. Once we accounted for other factors, this relationship diminished, reinforcing the inconsistency among these risk factors.

Across various countries, our findings recognized significant differences in how these factors relate to cognitive function. This suggests that the connections might mirror underlying issues rather than being straightforward risk factors that could be modified.

#Remedies and Their Impact

We also looked at whether remedies for these risk factors reduce negative relationships with cognitive function. For most factors, remedies did not seem to lessen the negative impact on memory. For hypertension, there was a suggestion that treating the condition might mitigate its effects on cognition, but this was not observed in the United States.

Overall, although many risk factors have known remedies, we did not find strong evidence that these remedies consistently lessen the negative relationship with cognitive function. This insight underscores the need for more extensive studies, possibly employing longitudinal designs, to grasp the connections better.

#Conclusion

In conclusion, establishing causal patterns that affect dementia risk is complex, primarily due to difficulties in observational studies. Many factors likely influence dementia risk over long periods, making it harder to pinpoint direct causes.

This analysis used data from multiple countries and aimed to test the robustness of previously suggested associations in the literature. We found that only a few relationships, such as those involving education, hearing loss, and depression, showed strong connections to cognitive function. For other risk factors, the evidence was weak or almost nonexistent.

The inconsistency across countries indicates that these risk factors may reflect other underlying issues rather than having a direct impact on dementia. Future research should aim to understand these connections better and explore the role of different factors in dementia risk.