Statcast Number 7 Transcript

DATE: May 14

PUBLICATION: “Wireless Substitution: Early Release of Estimates from the National Health Interview Survey, July-December 2007”

SPOKESPERSON: Stephen Blumberg, a senior scientist with the CDC National Center for Health Statistics, discusses the growing reliance on wireless telephones in the U.S.

BLUMBERG: There’s about 32,000,000 adults in the U.S. who are “wireless-only,” and there’s about 31,000,000 adults in the U.S. who are “wireless-mostly.” Ultimately that means about 3 out of every 10 adults in the United States receive all or nearly all calls on wireless phones

HOST: Statcast… May 14, 2008

HOST: Stephen Blumberg is a senior scientist with the CDC/National Center for Health Statistics, who is tracking the growing use of wireless telephones in U.S. households. The data come from the National Health Interview Survey.

Dr. Blumberg, why is a health statistics agency like NCHS collecting data on wireless telephone use?

BLUMBERG: NCHS collects data on wireless telephone use because of the number of telephone surveys about health that NCHS conducts… CDC in general conducts a number of health surveys by telephone and these telephone surveys typically do not include cell phones or wireless phone numbers in their sampling frame. So they don’t call them. That isn’t to say they can’t call them. But generally it’s more expensive, people aren’t expecting calls on their wireless phones. To the extent that people who are wireless only are different from people with landline telephones, these surveys may be biased because they don’t include them in the survey.

HOST: What sort of data-related problems are associated with the rise in wireless-only households?

BLUMBERG: Well, the wireless-only population in general has been described as “the young and the restless,” so young adults are more likely to be wireless-only …people who are their renting homes… people who are changing jobs often… tend to be more likely to be wireless only. These people also have different health characteristics than others. We know they’re more likely to be uninsured, for example. They’re more likely to binge drink and to smoke. On the other hand they’re also more likely to exercise more often. If these wireless-only individuals are not included in health surveys than these health surveys may be biased in their results – that is a telephone survey that use only landline telephones may underestimate the number of adults who binge drink or may underestimate the number of adults who smoke if they don’t include the wireless-only.

HOST: So what did your study find then?

BLUMBERG: Well, this study that we’ve recently released looked at data from July to December of 2007 and found the prevalence of the wireless-only population continues to grow. It’s been growing at a rate of about 2 to 3 percentage points every year. It found that it continues to grow among the populations that we were expecting to see it grow in – that is, young adults… adults who were renting their homes. But the other interesting news from this recent release concerns the “wireless-mostly” population. When I say “wireless-mostly” I’m referring to those adults who have both a landline and a wireless telephone, but who receive all or nearly all their calls on the wireless telephone. They may have a landline for their computer or their fax machine or their burglar alarm system but in general they receive their calls on wireless phones. What we were surprised to find was that the size of this wireless-mostly population was nearly equal to the size of the wireless-only population. That is, there’s about 32,000,000 adults in the U.S. who are wireless-only, and there’s about 31,000,000 adults in the U.S. who are wireless-mostly. Ultimately that means about 3 out of every 10 adults in the United States receive all or nearly all calls on wireless phones.

HOST: Is this phenomenon relegated to college students and other young adults?

BLUMBERG: Certainly that’s the group that most people think of when they think of the wireless-only population. And indeed young adults are more likely to be wireless-only. However if we look at the wireless-only population, only half of them are under 30 years of age. So that means that half the wireless-only population is over 30.

HOST: Are there any health risks associated with excessive or exclusive wireless phone use?

BLUMBERG: There certainly are people who have hypothesized that — these data don’t tell us anything about health risks related to cell phone use.

HOST: Do you expect that the number of wireless-only households will continue to grow?

BLUMBERG: We’re certainly seen it grow ever since we started tracking these numbers in 2003. I would expect it to continue to grow, and since 2003 it has been growing at a steady rate. Obviously it can’t sustain that rate otherwise you’d be above one hundred percent at some point. But for now we don’t see any suggestion that the prevalence or the growth of the prevalence of the wireless-only population is slowing down.

HOST: Our thanks to Stephen Blumberg for joining us on this edition of “Statcast.” “Statcast” is a production of the Public Affairs Office at the CDC/National Center for Health Statistics.