Universal pre-k improves kids' health in a hidden, powerful way, according to a new study

New York City is in the middle of a major initiative to improve the lives of children: universal pre-kindergarten.

The city, home to the largest school district in America, started an aggressive expansion of its pre-k program in 2014, based on a body of research that suggests pre-k can be a powerful, cost-effective way to give kids a skills boost as they enter the education system.

Any eligible four-year-old in NYC can now attend free, full-day pre-k. And that means all the kids going to pre-k now are spending their days in radically different ways than their peers born just a few years earlier.

That change is likely to impact the rest of these kids' lives.

A new paper, published by the National Bureau of Economic Research, investigates how pre-k impacts kids' access to healthcare. The results suggest that universal pre-k programs are improving the odds that kids who need treatment for vision, hearing, or asthma issues get the help they need.

There isn't public data that lists all the medical treatments children enrolled in pre-k are getting, so the researchers relied on a proxy: Medicaid data for New York City children.

Medicaid is a federal program that provides healthcare to low-income people and their children, and the population of parents who enroll their young kids in Medicaid in New York City closely resembles the population who sign their children up for universal pre-K programs.

Medicaid keeps detailed records of the treatments the system funds in different communities, so researchers Kai Hong, Kacie Dragan, and Sherry Glied looked at that data for New York City kids during the 2014-2015 academic year. Because that was the year the city most significantly expanded its pre-k program, the children were easily sorted into three groups: kids born in 2009 were too old to be impacted by the expansion, kids born in 2010 likely attended pre-k, and kids born in 2011 were still too young.

The researchers therefore considered kids born in 2010 as the experiment's "treatment" group, with kids in the other age brackets fitting into the "control" group.

Adjusting the numbers to account for differences in age and other factors, they found that kids eligible for pre-k were 2% more likely to get diagnosed with and treated for vision problems and 1% more likely to get treated for hearing problems.

The kids in the treatment group were also more likely to get diagnosed with asthma (kids born in early 2010 were 1.3% more likely than those in the control group to be diagnosed, and kids born in late 2010 were 2.1% more likely). They also had a higher chance of getting an immunization or infectious disease screening (kids born earlier in 2010 were 5.4% more likely, and kids born later in the year were 2.9% more likely).

Those numbers might not seem huge, but it's important to remember that the proportion of kids with serious illness is pretty low. So a 1% increase in the likelihood of diagnosis across a large population of kids can indicate a major shift for the children who actually need treatment. For example, the fact that the group of kids is 1% more likely to get hearing treatment overall means that hearing-impaired kids are actually 63% more likely to get treatment. For vision-impaired kids, the bump is 45%.

So why is pre-k changing health outcomes? The researchers suggest that putting kids in pre-k simply creates more opportunities for their health problems to get noticed, since early childhood teachers are often trained to spot them.

This might account for some of the long-term benefits associated with pre-k, they write:

If a young student's health conditions are well-managed-particularly sensory problems that could impede learning-then the child may have the chance to develop successful long-term learning strategies or problem-solving capacities in comparison to a child who remains burdened by undetected or poorly-managed conditions early in their education.

A significant amount of evidence suggests that undiscovered issues with vision or hearing are much less likely to get detected in poorer kids and can lead children to get frustrated or act out in class. Teachers then label those kids as difficult or disruptive - a label that sticks early on, and can be hard to overcome.

But when the likelihood of spotting kids' health issues increases, those small factors can improve their lives years down the road.