Lead exposure during childhood may lead to reduced cognitive abilities in later life, meaning people experience symptoms of dementia sooner, data suggest.
The study, one of the first to investigate the decades-long consequences of lead poisoning, suggests countries could face an explosion of people seeking support for dementia as individuals who were exposed to high lead levels during early life progress into old age.
“In the US, and I would imagine the UK, the prime years when children were exposed to the most lead was in the 1960s and 70s. That’s when the most leaded gasoline was getting used, lead paint was still common, and municipal water systems hadn’t done much to clean up their lead,” said Prof John Robert Warren at the University of Minnesota in Minneapolis, who was involved in the research.
“Those children who are now in their 40s, 50s and early 60s, will soon be entering the time of life when cognitive impairment and dementia are really common. So there’s this coming wave, potentially, of problems for the people who were most exposed.”
Although scientists have long known that children and adults who are exposed to lead have poorer cognitive and educational outcomes, few studies have investigated the longer-term consequences.
Warren and his colleagues combined data from the US-based longitudinal Health and Retirement Study (HRS), which has followed the brain health of thousands of adults over several decades, with census records to pinpoint where 1,089 of these individuals lived as children. They also mapped the locations of towns and cities that used lead pipes and had acidic or alkaline water – a proxy for high lead exposure.
The research, published in Science Advances, revealed that people who lived in cities with lead-contaminated water as children had worse baseline cognitive functioning – a measure of their ability to learn, process information, and reason – at age 72, compared with those who did not. The difference was equivalent to being roughly eight years older.
Warren said: “Most people tend to think of lead as a yesterday problem. We got rid of leaded gasoline and lead paint, and we’re doing what we can to clean up water, so we tend to think of this as a problem that we’ve kind of solved. But unfortunately, the long-term damage of all that lead exposure may still be felt in the coming decades.”
Although childhood lead exposure doesn’t necessarily mean a person is at greater risk of dementia, “they are starting out at a substantially lower point, and so they are potentially going to get to problematic levels of cognitive impairment earlier,” Warren added.
The good news is that the team found no difference in the rate of cognitive decline between the two groups – possibly because their cognitive function was tested after any brain damage due to lead exposure had taken place.
Dr Haena Lee at Sungkyunkwan University in Seoul, South Korea, who led the research, said: “More research is clearly and urgently needed to better understand the lifelong implications of childhood lead exposure for brain ageing and to identify effective interventions to mitigate lead’s long-term consequences.”
