The first study was conducted in 2004 and 2005 by a team led by Dr. Ashok Agarwal of the Cleveland Clinic. It analysed 361 men who visited an infertility clinic and found that sperm count and quality was "significantly lower" in those men who used cell phones for more than fours hours per day.
Agarwal is now in the "early stages" of a follow-up study, although it is too early to say how many men will be studied or to discuss other details, a spokesman for Cleveland Clinic said in an interview. Agarwal was unavailable for comment.
Agarwal presented findings of the first study at a medical conference in October 2006, which led to a flurry of news coverage at the time. Recent publication of the findings on the web sparked a spate of articles on the web and on national television newscasts.
Agarwal and his associates published the results in a scientific journal, Fertility and Sterility and also in a shorter form in Urology News.
The Urology News article appeared last year, but the longer version was distributed at sciencedirect.com last month, which apparently led to the recent surge in media attention, said clinic spokeswoman Lisa Bast.
"There's been a lot of attention on the story, and we've had several calls in the last couple days," said Cleveland Clinic spokeswoman Lisa Bast.
Agarwal reportedly told Reuters in a story widely posted on the web last week that the original study is being followed by two studies on the topic, one with a larger group. However, Bast said there is apparently actually only one follow-up study underway.
The first press attention on the topic occurred after Agarwal presented the results in October 2006 to a medical conference, she added. But the revived attention is probably because of the publication of the full data, she said.
Responses to the news articles on the web blasted the research for surfacing again when it concerns a relatively small research sample.
"Wasn't that the same study from a while ago that was written about in the press in 2006?" asked Joe Farren, a spokesman for the CTIA-the Wireless Association. "You can't draw any conclusions from that."
Farren said CTIA and its wireless carrier members have been careful to track studies regarding any impact from wireless usage on the human body. "We support good science and always have," Farren said. "It's important to look at studies that are peer reviewed and published in leading journals and to listen to the experts."
Farren said CTIA has found in looking through many studies that "there is no association between health risks and wireless usage." That goes for the impact of wireless usage on the brain or any part of the body, he added. Federal regulators limit the electromagnetic frequency emissions from phones, and manufacturers EMF emissions are well below those limits, he said.
Farren pointed to a study out of Japan released last week that discounts previous links between cell phone use and cancer.
And he noted that the American Cancer Society has said that cell phone use and cancer is one of the "Top 10 Cancer Myths."
However, the National Cancer Institute has laid out a summary of research into the subject, and notes on its website that, "Overall, research has not consistently demonstrated a link between cellular telephone use and cancer or any other adverse health effect."
As for the impact of cell phone usage on sperm quality, Farren said CTIA is awaiting the results of further study.