Aetna announced late Wednesday after the market closed that it is laying off 625 employees. One hundred and sixty of those employees work in Connecticut. Aetna says the layoffs are the result of a decline in membership and the economic downturn.

“The economic downturn has had a significant impact on our customers,” Aetna Chairman and CEO Ronald A. Williams, said in a statement. “In addition, we must prepare for the impact that health care reform and regulatory changes may have on our business.”

An Aetna spokesman said it had 19 million members at the beginning of the year and now it’s down to 18.7 million members. The decline is expected to continue in 2010 and more layoffs are anticipated.