Health researchers have noticed that some groups of people are more consistently healthy than others, and wondered? Is it race? Income? Where you live? In the United States, these disparities in health outcomes have been the focus of intense research for the past several decades.

Harvard University health policy researcher Ellen Meara says scholars have found some clues as to why some groups of people have more or less disease than others. She says one important factor in people's health is the amount of education they have.

In her most recent paper, Meara looked at data from the United States census. These counts of people occur every 10 years. Meara and her colleagues examined data from several decades.

"We looked at life expectancy at age 25," Meara says.

"How many additional years can you expect to live if you arrive at age 25 and your education has stopped at high school, or sooner? Versus how many years, can you expect to live if you've reached aged 25 and you've gone on to at least some college?"

Meara says they found that in 1990, a 25-year-old who only had some secondary school could expect to live for a total of 75 years. In 2000, a 25 year old with some secondary education could also expect to live to the age of 75.

In contrast, for a better educated 25-year-old, they could expect to live to the age of 80 in 1990. Someone with a similar education level in the year 2000, could expect to live to be more than 81 years, 81.6 years to be exact.

Meara says, not only do better-educated people live longer to begin with, but over just ten years, more educated people made gains in the length of their lives. Meanwhile, the life expectancy didn't change for less educated people.

Some of these gains can be explained. Meara says researchers know that people who are more educated are more likely to quit smoking cigarettes, or not start at all, compared to people with less education.

"I think it's a reminder not to be complacent," Meara says.

"Just because a population overall appears to be getting healthier, it doesn't always mean that those advantages and successes that many people have enjoyed really extend into all parts of the population. And I think that's something to really pay attention to regardless of whether you live in the US or elsewhere."

Meara points out that education often determines income - people with more education frequently make more money. This makes them better able to access health care, and purchase other resources and services that can keep them healthier. But the data on income do NOT show that people who make more money are automatically healthier.

Meara says education is key. People need to be educated in order to take advantage of opportunities for better health.

Her research appears in the journal Health Affairs.