Lower socioeconomic status can triple the risk for dementia among individuals under 65 years old

People from lower socioeconomic backgrounds have three times the risk of developing early-onset dementia. And if those same people lead an unhealthy lifestyle, the risk is 440% higher when compared with individuals from a higher socioeconomic class that lead a healthy lifestyle. These numbers are from a study by researchers from the University of Science and Technology in Huazhong, China, and were recently published by the magazine Lancet Healthy Longevity.

“Our study is one of the first to examine the complex relationships between lifestyle, socioeconomic level and risk for early-onset dementia among people from 37 to 60 years old. Lifestyle and socioeconomic level are significantly associated with early-onset dementia, although the connection with the second factor is much more apparent,” Gang Liu, professor from the University of Huazhong’s School of Public Health and lead author of the study, told EL PAÍS in an email. The expert says that, after adjusting for diverse risk factors, a person from a low socioeconomic level has a 258% larger risk of developing early-onset dementia when compared with people from a high socioeconomic level. People with three or four healthy lifestyle behaviors have a 40% lower risk for early-onset behavior as compared to those with one or no healthy lifestyle behaviors.

For the study, its authors used the data from 440,000 participants in the United Kingdom’s Biobank between the ages of 37 and 73 years, which they followed for 12 years, monitoring indicators like life habits, and with a variable of socioeconomic status determined by a combination of education, family income and employment. One of the most surprising findings for the researchers, says Liu, is that only 12% of the cases of early-onset dementia associated with socioeconomic level could be explained by lifestyle factors. This suggests that people from lower socioeconomic levels cannot necessarily mitigate their risk of developing early-onset dementia by leading a healthier lifestyle.

“The mechanisms underlying the relationships between socioeconomic inequality and early-onset dementia remain to be explored by future studies, but what seems clear is that socioeconomic status may itself affect individuals’ cognition,” says the author. “For example, higher education may result in enhanced cognitive reserve that can compensate for neurodegeneration; poverty may also directly affect cognitive ability, as poor financial status can lead to excessive mental workload, stress, anxiety or depression, which some studies suggest may have a link to dementia,” he adds.

“This is a very robust study that puts a twist on what we already knew about the impact of lifestyle, because it seems that socioeconomic status alone is an important factor in increasing the risk of developing dementia,” says David Pérez, head of the neurology department at Madrid’s University Hospital October 12 and member of the Spanish Society of Neurology. The neurologist points out that precarity can affect brain health in many ways, including lifestyle: “On the other hand, there is the stress generated by this situation, or the greater prevalence of depressive disorders, but there are other difficulties. For example, to adhere to a Mediterranean diet, [if one is of lower socioeconomic status] one is more likely to do more routine, less motivating, less intellectual work, and also to do it for longer hours, which means you will have less time to do physical exercise or control your cholesterol or hypertension.”

The fight against inequality

Early-onset dementia refers to the cases of dementia in which it is diagnosed in patients younger than 65 years old. According to a 2021 study, the rate of this kind of dementia is around 119 cases for every 100,000 individuals, which means it affects 3.9 million individuals around the world. In Spain, although there is no official registry, between 600,000 and one million people suffer from dementia, which suggests that between 10% and 15% (around 70,000 cases) would be early-onset dementia. In the preamble to the 2019-2023 integral plan for Alzheimer’s and other dementias put out by the Spanish Ministry of Health, focusing on dementias is “a public health priority and a social and health problem of the first order that has become the great, silent epidemic of the 21st century, and a great challenge to the sustainability of any social and health system.” This use of the word “epidemic” is not trivial. According to data from the World Health Organization, more than 50 million people worldwide suffer from dementia, a number that is expected to rise to 75 million by 2030 and 132 million by 2050.

“It’s important to remember that, in Western countries, especially in Europe, during the last two or three decades, we’ve seen a drop in rates of dementia that has gone a little unnoticed because, as the population has aged, the number of cases is growing,” says Pérez. The expert explains that this drop is largely due to welfare programs, “which have allowed many people access to quality public education, quality public health care and a better standard of living. Now we have other challenges to attend to, such as trying to implement public policies that allow us to move towards reducing social inequality, because we have seen that this, directly or indirectly, prevents dementia,” he says.

For Unai Martín, professor of sociology at the University of País Vasco and a member of a Spanish Society of Epidemiology work group on social health determinants, this study is of the utmost importance because, due to its robustness, it bolsters the argument for something that experts have been calling out for decades: the fact that social inequality causes disease, and that as a risk factor, it is as or more important than other factors that science and medicine have traditionally assigned greater importance.

“A lot of the time, even when we understand that inequality is important, we tend to think that the way to work on health inequalities is to work on lifestyle habits. And this study shows that strategy to be in error, that if we don’t work on the fundamental factor, which is social inequalities, nothing else will be of much use. It’s a matter that we have a hard time understanding when it comes to taking action. In fact, a lot of today’s public health campaigns continue to be focused on habits,” says Martín, who thinks that centering attention on lifestyle habits is, in addition to a way of blaming the victim, a way for authorities to avoid responsibility. “They smoke more, they do less exercise, they eat more poorly, we say, and we try out strategies to get them to stop smoking, to exercise, to eat better. But a lot of the time, people don’t even have the option to eat better or exercise!” he says.

According to Liu, although we can’t ignore the importance of promoting healthy lifestyles at the individual level, the study backs up the need, in order to reduce the rates of dementia, for governments to adopt public health measures to improvement social health determinants and promote equality.

That’s an opinion shared by Martín, who considers the fight against social and economic inequalities to be one of the best possible strategies for addressing the massive challenge of dementia. “First of all, this is a question of social justice. And that’s also true because improving health depends very little on what we do within the health system. The health system is very good at curing disease, rescuing people when they become ill, but if we want to better people’s health at a societal level, you have to go beyond the health system to act on certain policies (urban, rent, education, etc.) that reduce inequality, because that will also reduce pressure on the health system,” says the Spanish Society of Epidemiology spokesperson, who laments how, traditionally, on a political level, it is so hard to think in the medium and long term, which is precisely what these policies require. “It’s very easy to understand that we have to treat a person who has suffered a heart attack or suffers from dementia, but it is harder for us to understand that for those people to not suffer from heart attacks or dementia, we have to act on certain factors that can delay or avoid these ailments. Therein lies today’s key to improving health,” he says.

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