Understanding lifespan influences on cognitive ability

Assistant Professor of Gerontology Joseph Saenz joins Professor George Shannon to discuss his ongoing work on rural-urban differences in cognitive ability among older adults in Mexico, as well as whether certain personality factors make people resilient to the negative effects of early-life disadvantage.

Quotes from this episode

On the focus of his work

I focus my research on looking at how it's socioeconomic disadvantage throughout the life course relates with cognitive ability and late life. I'm interested in education. I'm interested in income, wealth and the resources that we have available to us throughout our lives and how this relates with better cognitive functioning, as well as lower dementia risk and the population of older adults of Latino origin here at the United States and also older adults in Mexico.

On demographics and differences between rural and urban populations in Mexico

One of the things that's very important about the Mexican population is we've seen a lot of demographic changes over the past century. In addition to seeing rapid population aging with the share of the Mexican population aged 60 and over increasing rapidly. We've also seen a large urbanization process where people are going from rural areas to urban areas. For example, back in 1920, only about 70% of the Mexican population lived in rural areas, but by 2010, this had declined to only about 20%. So a lot of people have been going from rural areas to urban areas. And this is important because in Mexico we see a lot of differences of a lot of disparities between urban areas and rural areas.

Rural areas tend to be disadvantaged in several ways. They tend to have lower access to education. There's fewer schools for people to go to. And the educational quality that people got, especially if you look at several decades ago was significantly lower quality than their urban counterparts. Also in rural areas, we tend to see higher rates of poverty and various measures of SES. And we also see that the rural population tends to have less access to healthcare. This as the gap between the rural and urban areas in terms of healthcare access has shrunk a little bit over the past couple of decades, but there's still a disparity there. And so when you bring up the idea of the life course and where people live throughout life, I think this is especially important in Mexico, where we saw that rural to urban population shift, that many people who are living in urban areas now were living in rural areas as children.

 On his research looking at where people live throughout their lives

In this more nuanced approach, what we see is that the people that had the lowest exposure to urban areas throughout life, those who lived in rural areas in early and late life, ended up doing the worst cognitively. And those who are doing the best are the people that lived in urban areas in early life and urban areas that late-life... And what we also see is that compared to people that stayed in rural areas throughout their entire lives, those who went from a rural to an urban area, also show advantages. So what it looks like we're finding in our current studies is that both early life, urban-dwelling and late-life urban dwelling are related with better cognitive ability. And there is an advantage that comes from moving to an urban area throughout life.

On the negative impacts of indoor air pollution

And then the other reason that we could expect to see these differences between rural and urban areas is that in urban areas, we know that people have high exposure to air pollution from the outdoor environment. When we look at pictures, for instance, say in Mexico City, we see the smoggy skies and we see this high level of air pollution that people are breathing in urban areas. However, in rural areas in Mexico, a significant portion of the population relies on solid cooking fuels. So this could be wood and coal and Mexico is primarily coal if people are using solid fuels for cooking. And when people use these solid fuels for cooking, particularly inside the house, you can imagine how quickly the pollution builds up inside the home. So people in rural areas have greater exposure to air pollution inside the home from solid cooking fuels. And we know that that exposure to air pollution is associated with poor cognitive functioning. And in my own work, looking at the effects of indoor air pollution from solid cooking fuels, I find that people who cook with these solid cooking fuels tend to have lower cognitive functioning and also more rapid cognitive.

On the potential to improve outcomes

We've seen several large policy changes in Mexico in the past couple of decades that are aimed at improving access to healthcare and primarily in rural areas. And so improvement of access to healthcare, access to health insurance, and regularly seeing doctors are something that we could use to improve cognitive ability and cognitive outcomes of older adults in rural areas. And last on the topic of cooking fuels, we know that one of the challenges and one of the reasons that people in rural areas are more likely to use these solid fuels is because maybe there's not the infrastructure to bring clean cooking fuels such as gas and electricity to more remote rural areas. Policy changes aimed at improving infrastructure to bring clean cooking fuels to rural areas and to educate people on how to cook with clean cooking fuels could be something very important to bridging these disparities that we see across rural and urban Mexico.

On the role of cognitive resilience and personality characteristics in overcoming the negative effects of early life disadvantage

What cognitive resilience is looking at is one's ability to not show the negative effects of stress. So people who are cognitively resilient can experience stress but don't show effects on cognitive functioning. They look like they're doing okay, cognitively, even though they're experiencing high levels of stress. In my work related to personality, I look at how personality characteristics are related with one's cognitive resilience or one's ability to overcome the negative effects of early life disadvantage. Early life disadvantage, being a stressor that I'm considering.

So the personality characteristics that I tend to look at include a locus of control, which is how strongly one feels that he or she has control over their lives. And people who have an internal locus of control tend to think that the things that happen to them are the results of their own work. That they're the results of their own choices. Whereas people who have an external locus of control tend to believe it's external influences that affect their life. And so they're the ones that tend to believe that maybe the bad things or good things that happened to them throughout life are the example are, are the result of luck or of chance.

Now, the other personality characteristic that I look at is conscientiousness, which has one's tendency to plan,  one’s tendency to be goal-oriented and to delay gratification. And when we look at the locus of control and when we look at conscientiousness, both of these affect how people tend to cope with stressors. So in my work on personality, what I do is I look at how personality relates with one's ability to overcome those effects. And we see that having an internal locus of control and having a conscientious personality are both independently related with one's ability to overcome the effects of early life disadvantage.

On the importance of midlife research

We also see a lot of focus on early life, a lot of looking at early life SES, a lot of research looking at education and childhood, but I don't think we see nearly enough work looking at mid-life. I think there's a big gap in our understanding of the courses or the trajectories that people take throughout life. We don't see enough about midlife. So I think this is another area that I'd like to go into more in terms of looking at midlife. So what are the specific occupations that people worked? What are the levels of cognitive stimulation and those activities also looking at midlife, we could also look at people's marital histories when they got married, whether they were married multiple times. So I think there's a lot of information out there on midlife that could be very valuable in predicting where people are going to be 10, 20 or 30 years down the road.