A self-proclaimed “data nerd,” Rob Warren has linked U.S. Census data and information from University of Michigan’s Health and Retirement Survey (HRS) to create the first estimate of the long-term consequences of childhood lead exposure.
Warren, a professor of sociology at the University of Minnesota, and a team of his colleagues recently published a study in the journal Science Advances. It found that adults who were exposed to lead in their drinking water as children performed worse on HRS cognitive assessments in their late 50s and early 60s.
Connecting these two data sets helped reveal the important connection between lead exposure and cognitive impact, something that had never been done before.
And the worst effects could be yet to come, as it will be a few years before the generation that experienced the greatest levels of lead exposure becomes old enough to participate in the HRS.
“We haven’t yet seen the true impact,” Warren said.
This conversation has been edited for length and clarity.
MinnPost: What got you interested in this line of research?
Rob Warren: I do a fair amount of research on how early-life experiences shape later-life health and continuing outcomes. We all know about the short-term negative impact of childhood lead exposure. But what about the long-term consequence of childhood lead exposure — if a person is exposed to lead in their drinking water as a child, how will it impact them several decades later in respect to reduced cognition and increased dementia risk? That question fascinates me.
MP: Pulling this information together required linking several important pieces of data. How did you do that?
RW: To do that research you need studies where you can identify exactly where kids lived, the levels of lead they were exposed to in their drinking water, and then identify its impact on their cognition later. Only recently did we have a representative sample of Americans that we could study.
MP: How did you identify that representative sample?
RW: I’m a data nerd. Here’s an important factoid: U.S. Census data becomes public after 72 years. We just had part of the 1950 Census released on April 1 of this year. Everything is now public from 1950 backward: Everybody’s name, street address, education, income. You have complete information for the 1940s and now the 1950s have just been released. This project starts with the 1940s in the U.S.
What we know about cognition in later life comes from studies of older people. The biggest study is the HRS. They survey older people, a random sample of people age 50 and older. They interview them every two years until they die. They have been doing that for a long time. We don’t know anything about these people before age 50. We don’t know where they lived when they were children.
But we were able to work with HRS to locate participants and then look up those participants in the census when they were children in the 1940s. These people are now in their 60s, 70s, 80s, 90s. Now, with the help of public Census data, we know exactly where they lived as kids. And from the HRS we have accurate measures of their rates of dementia and other health risks. All of this work linking HRS to the Census is done in a highly secure computing environment so nobody can ever get ahold of their information.
MP: How did linking these two sets of data allow you to study childhood lead exposure?
RW: In the 1940s, most municipal water systems had lead. We know how much. There are good records for every municipal water system in America about what kind of pipes ran into every person’s home. We also know what the pH levels in the water were. It turns out if you had lead pipes it was okay if the water in your community wasn’t too acidic or too alkaline. For all of these HRS participants we know what the pipes were made of in their towns and also the pH levels of their water. So we know if their drinking water was contaminated with lead.
MP: What did you learn about the impact of drinking water contaminated with lead on general cognition and long-term risk of dementia?
RW: The people in HRS study have cognition measures taken every two years. We first see them when they are in their late 50s, then every two years after that. We see how they are performing on certain tests. The bad news is that everybody’s cognition declines as they age. But people who were exposed to lead as children start out lower than their peers at about age 60. If you start out lower and decline as you age, you reach problematic levels of low cognition earlier in life. If you weren’t exposed to lead as a child, you still decline but you don’t reach problematic levels until much later. The people who were exposed as children get to that point years before those who were not exposed.
MP: Did your study find that socioeconomic factors played a role in lead exposure and risk of dementia?
RW: Not really. In the ‘40s there was very little public health knowledge about lead exposure being a problem. There was nothing you could do about it. And nobody did anything. They didn’t have Brittas or lead-filtration systems. Everyone in Minneapolis drank the water: Rich, poor, white, Black, immigrants, non-immigrants.
Because everybody in the city drank the same water it was more equitable in that way. Nowadays if you were going to do that you’d find that wealthier people can afford to have water filters or they only drink bottled water or do other things to avoid ingesting the lead or they were able to get the city to replace the water lines in their part of town.
MP: Because they are now aware of the risks, communities have reduced lead levels in their water and in the air. Will certain generations feel the impact of lead exposure more than others?
RW: If you look at how much lead children would have been exposed to, based on what we know about leaded gasoline and lead paint and water systems, the people who would have been the most exposed to lead are people who were children in the 1960s and 70s. People were driving cars with leaded gasoline a lot more then. It was just before we got rid of lead paint. So these are the decades when children were the most exposed to lead. If you do the math, this group is not quite old enough yet to be experiencing dementia.
MP: Sounds like you’re talking about members of Generation X.
RW: The big-scale cost to public health and cost to people is still coming. I’m 53. These people are my age. The people who were most exposed to lead in childhood haven’t felt the full consequences of this exposure yet. The first time I gave this as a presentation, I had everyone in the room who was a child in those years raise their hands. It led to an uncomfortable silence.
MP: Is there anything a person can do to limit the future impact of childhood lead exposure?
RW: When you are exposed to lead as a kid, some of the lead naturally filters out of your body. Lead and calcium get confused by the body so a lot of lead gets stored in your bones until you are old enough to experience osteoporosis or other diseases that lead to bone loss. That’s when the lead comes back out into your bloodstream. If people were exposed to lead in childhood, there are things like certain medications and weight-bearing exercises that they can do to prevent bone loss that will ultimately prevent lead from recirculating in their blood. If lead doesn’t circulate in the blood, it is not going to hurt anything.