Health is rapidly becoming a hot topic in the blogosphere, and marketing–whether self-promotion or the promotion of others’ products–is becoming more prevalent among health-related blogs, according to new research.

A survey from health care marketing communications consultant Envision Solutions finds that nearly half of all American adult bloggers have written about a health-related subject, and 60% of those bloggers write primarily on health-related topics. The company estimated that more than 13 million Americans posted at least one health-related item to a blog between February and August 2008.

“[Health blogging] has exponentially grown over the past two years,” says Fard Johnmar, founder of Envision Solutions. “Once dominated by medical professionals, the health blogosphere has grown to incorporate a diverse range of people in the United States.”

Health-related blogs also span many different demographics, Johnmar says. More than half–057%–of health bloggers are women and 38% are African-American or Hispanic. Half of health-related bloggers were between the ages of 18 and 34, according to the survey.

While one-third of the respondents said they were blogging to educate others about a condition or malady, 21% of them said they blogged primarily for marketing purposes, such as a doctor who looked to increase business for his or her practice, or a health care consultant wishing to demonstrate expertise in a subject or health policy.

Only 7% of the respondents said they were blogging to help cope with a medical condition, and 10% said they were doing it to advance a cause.

Outside of personal marketing, 46% of the health care marketing professionals said they had been contacted by PR professionals to promote a product or service–up 29% in the 2006 survey, Johnmar says. Thirty-five percent of the bloggers said they were running advertisements on their blogs, compared with 27% in 2006.

Despite those findings, nearly three-quarters of the bloggers — 73%–expressed confidence that their peers were disclosing conflicts of interest. (In a finding that may be related, nearly 20% fewer bloggers reported posting anonymously than in the 2006 survey.) Seventy-nine percent of health bloggers said a person’s background and biases have a greater influence than advertising
on credibility.