The growing use of cell phones has reshaped day-to-day lives, from being able to reach almost anyone at any time to putting the Internet in a person's pocket. And despite a few common gripes such as losing a signal or running out of minutes, cell phones have no doubt made life more convenient--for the most part.
There is at least one group of people for whom cell phones have become a bit of the proverbial thorn in the side: health researchers. The problem comes into play for researchers and surveyors who collect what is often essential health data via phone, relying on a randomized sampling of telephone numbers to bring back information and inform conclusions that users of such data can deem representative. Historically, this was not difficult--telephone numbers were readily available, corresponded with a person's geographic location and usually belonged to an adult. But today, growing numbers of people have no landline at all, only a cell phone, and general assumptions about who will be at the other end of a phone call are quickly shifting. Still, these are secondary concerns. The primary concern is whether cell phone numbers are included in the survey design in the first place--a less-than-easy task, but one that is becoming more important in gathering truly representative data on people's health and behaviors.
"The survey research industry is in a time of upheaval," said Stephen Blumberg, PhD, senior scientist with the National Center for Health Statistics at the Centers for Disease Control and Prevention. "The survey modes and methods that worked reliably for the past decade or two need to be rethought. I fully expect that we will come out of this with new modes and new methods that continue to accurately reflect the behavior and attitudes of the public ... Right now is a time of challenge, but a time of interesting experiments and new opportunities."
Since 2003, the National Center for Health Statistics has been tracking the prevalence and characteristics of wireless-only--aka cell-phone only--users, putting out reports every six months on their numbers as well as their health-related behaviors. One such report, released in May, found that the "number of American homes with only wireless telephones continues to grow." According to "Wireless Substitution: Early Release Estimates from the National Health Interview Survey, July-December 2008," which Blumberg coauthored, more than 20 percent of surveyed homes had only wireless telephones during the second half of 2008, an increase of almost 3 percent from the first half of 2008--a number that represented the largest six-month growth in wireless-only users since the center began collecting such data. In addition, more than 14 percent of American homes received all or nearly all phone calls on cell phones despite also having a landline. The biggest predictor of whether a household is wireless-only is whether the residence is owned or rented, with renters four times as likely to be wireless-only.
The demographics and health statuses of wireless-only users make their inclusion in health surveys important as well. According to the May report, men and those living in or near poverty were more likely to live in households with only wireless phones as are black and Hispanic adults. Binge drinking, smoking and being uninsured were more likely among wireless-only users, researchers found, but they were also more likely to be physically active, more likely to report being in good health and more likely to have been tested for HIV.
Blumberg noted that even when controlling for age, income and home ownership, such health characteristic differences still persist and while the data isn't available to specifically explain why, Blumberg had some guesses. Perhaps, he said, "people who choose to be readily available to all of …