Nearly 24 million Americans — or 10% of the entire online population — visited a health insurance website in the fourth quarter of last year, with Aetna logging the most visitors, new research suggests.

Reston, Va.-based comScore, a digital measurement company, found that 23.8 million Americans visited either sites of insurers or aggregators, including online health insurance brokerages.

“Consumers are increasingly turning to the Internet as one of their first destinations to research health insurance, whether it is gathering information to evaluate options or seeking answers to questions concerning their current provider,” said comScore director Susan Engleson in a statement. “Having a strong online presence serves as both a gateway to consumers as well as an important branding opportunity for health insurance organizations.”

Other possible reasons for the numbers include people doing research in preparation for the annual open-enrollment season, and the lingering effects of the recession causing more people to seek alternatives to employer-based insurance they used to receive or to find cheaper options available to them. Also, awareness of health insurance costs and coverage has been heightened as Congress and President Barack Obama continue to debate possible reform to the nation’s health insurance system.

In all, nine companies had more than 2 million web visitors. Aetna’s websites had the most visits, with 4.8 million or a 20% industry penetration, comScore reported. The websites of Blue Cross Blue Shield affiliates across the country followed, reaching 4.1 million visits or a 17.4% penetration.

USInsuranceOnline. com, an aggregator, had 4 million visits and a 16.8% penetration, while Kaiser Permanente had 3.1 million visits and a 13.2% penetration. Another aggregator, eHealthInsurance. com, followed with 2.8 million visits (11.6%), ahead of CIGNA’s websites, which had 2.6 million visits (11%).

Rounding out the top nine were WellPoint’s websites, reaching 2.2 million visits (9.4%), Humana’s websites, drawing 2.1 million visits (8.6%). Other health insurance providers whose websites claimed a portion of the market share include Coventry, IndividualHealthQuotes .com, Vimo. com, GoHealthInsurance .com, Health-Plan-Quote .com, HealthInsuranceSort .com, Assurant Health, MedHealthInsurance .com, HealthQuoteExpert .com.

Engleson added that the Internet is a “critical channel” for health insurance providers and that consumers are “displaying increasing comfort in turning to the web to obtain this often complex information.”