STATE COLLEGE — Pennsylvania is showing its gray in Census figures being released today, with the median age of residents having inched past 40 as the first baby boomers approach retirement age.

Counties in rural northern Pennsylvania, as well as areas in western parts of the state once teeming with steel mills and coal mines were among the oldest in the commonwealth, according to the statistics from the 2010 head count providing fresh evidence of a long-developing trend.

Also factoring in is the maturation of the massive baby boom generation, the oldest of whom turn 65 this year. Plus, the percentage of Pennsylvania homes with children dipped to 29.9, down from 32.6 percent in 2000.

The consequences are broad in Pennsylvania.

While leaders try to reverse the “brain drain” of young, educated residents to warmer or more lucrative locales, state lawmakers mull balancing the needs of a population living longer while trying to cut into a massive budget deficit.

“It impacts everything from housing to transportation to child care. Cultural institutions, medical care and even the trajectory of how people define their lives,” said Dr. Neil Resnick, director of the University of Pittsburgh Institute on Aging. “Most people born now have a good chance of making it to 100, so in that context why would you need to figure out what your major is by 21 or 22?”

The median age of Pennsylvania’s 12.7 million residents in 2010 was 40.1, up from 38.0 in 2000, according to the latest batch of census data that sheds more light on age and household makeup. Data for all states have yet to be released, so a national comparison can’t be made.

A separate Census Bureau survey in 2009 had Pennsylvania tied with New Hampshire for the fifth-oldest median age in the country behind Maine, Vermont, West Virginia and Florida.

There was a 29 percent increase in the number of residents age 85 and older to more than 305,000, though they represent just over 2 percent of the population.

“It just means increased demands for social services and a political conundrum for politicians who want to cut funding for them,” said G. Terry Madonna, a political scientist at Franklin & Marshall College in Lancaster.

There was a 2 percent jump in the number of residents 65 and older to about 1.9 million, or about 15 percent of the population.

But the 2010 count was taken at a time when the oldest baby boomers — those born between 1946 and 1964 — were just a year from retirement age of 65. Those residents began celebrating their 65th this year, a demographic wave so large that researchers have referred to it as the “aging tsunami.”

As of 2010, the number of Pennsylvanians age 45-64 rose about 25 percent to more than 3.5 million. They make up 28 percent of the state’s population, up from 23 percent a decade ago.

Medical advances, a focus on healthier lifestyles and better management of chronic diseases have Americans living longer.