two emerging issues in epidemiologic research access to populations for epidemiologic study side...
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Two Emerging Issues in Epidemiologic Research
• Access to populations for epidemiologic study
• Side effects of specialization
Issue #1: Access to Populationsfor Epidemiologic Study
• Often use pre-existing data
• But need primary data collection when:– No surveillance system exists
– Need exposure data not already available
• Common situation: population-based case-control study
• Present in ~95% of U.S. households
• Used for sampling, data collection, or both
• Random digit dialing (RDD)– Yields probability sample
– Captures unlisted phone numbers
Number of MedLine Citations with “Random digit” and “Epidemiologic-methods” by Year
0102030405060708090
100
1975-9 1980-4 1985-9 1990-4 1995-9 2000-2
Calendar year
Now-Standard RDD Refinements
• Distribution of calls among weekday, evening, weekend
• Later recontacting and conversion of “soft refusers”
• High-yield sampling methods:– Mitofsky-Waksberg two-stage sampling
– List-assisted sampling
Reported Participation among Controls in 69 Case-Control Studies, by Year of Publication
(Olson, 2001)
Source: Am J Epidemiol 2001; 154:574-81
Trend in Response Rates in CDC Behavioral Risk Factor Surveillance System, 1994-2000
0
10
20
30
40
50
60
70
80
1994 1995 1996 1997 1998 1999 2000
Calendar year
Source: BRFSS 1998-9 Quality Control Reports
Trend in Calling Effort in Behavioral Risk Factor Surveillance System, 1995-1999
0
1
2
3
4
5
6
7
1995 1996 1997 1998 1999
Calendar year
Phone numbers called per
eligible respondent
Source: BRFSS 1999 Quality Control Report
“And to think if I hadn’t been home having dinner I might have missed this wonderful
investment opportunity.”
Impact of Telemarketing in the U.S.
• Employed ~6 million people in 2001
• Generated $257 billion in direct sales to consumers in 2000
• ~19 billion telemarketing dialings each month
• “SUGging” - Selling Under the Guise of a survey
• “FRUGging” - Fund Raising Under the Guise of a survey
Other Contributing Factors
• More single-person households
• More households in which all adults work outside the home
• Answering machines
• Caller ID
“As of July 2002 CMS will no longer release the Medicare Names and Addresses file to researchers. CMS has imposed a moratorium on the release of this file as means for notifying beneficiaries about research studies.
“We are reevaluating our procedures to ensure that we continue to have in place the best privacy protections for Medicare beneficiaries.”
Source: www.cms.gov/data/requests/moratorium.asp, accessed 6/5/03
Center for Medicare and Medicaid Services Moratorium
Some Unfortunate Possible Responses
• Use only pre-existing data
• Use only populations of convenience– Self-identified volunteers
– Existing samples from prior studies
– Familiar, easy-access settings: workplaces, etc.
• Shift work abroad
Some General Measures We Can Take
• Work toward more standardized reporting of study participation
• Promote a positive public image of epidemiologic research– Feed back interesting information to participants
– Be mindful of respondent burden
– Minimize discomfort
• Scrupulously protect privacy and confidentiality
Specific Coping Strategies:1. Worry More Selectively?
• Bias due to non-response depends on:
(a) Proportion who participate
(b) Extent of difference between participants
and non-participants
• Sometimes (b) is small
• But can’t always predict when
Specific Coping Strategies:2. More Incremental Improvements to RDD
For example...
• Use answering-machine messages to distinguish research from telemarketing
• Increase number of call-backs
• Optimize selection and training of interviewers
• Offer incentives for participation
Percentage of U.S. Households with Internet Access by Annual Household Income, 2001
0 20 40 60 80 100
<$5K
$5-10K
$10-15K
$15-20K
$20-25K
$25-35K
$35-50K
$50-75K
$75K+
Source: Bureau of the Census Current Population Survey
Percentage of Households
Possible Future Portals of Access to Populations: 1. Internet
• Useful data-collection method once study participation arranged
• Not (yet?) a promising successor to RDD for sampling
Possible Future Portals of Access to Populations: 2. Cellular Phones
• Linked more to individuals, not households
• Population coverage may become very high
• Fewer calling plans charge for incoming calls
• Text messaging or other features may permit
initial contact without annoying interruptions
Some Currently Available Alternatives
• Area sampling
• Lists
– Commercial mailing lists
– Drivers license records
– Voter registration lists
– Other: town lists, dwelling units, etc.
Issue #2: Side Effects of Specialization
How epidemiologists vary:
• Chronic disease / Infectious disease
• Clinical training / Non-clinical background
• Academia / Government / Industry / Other
• Basic research / Field epidemiology
• By disease or exposure area
Side Effects of Specialization
• Fragmentation and
compartmentalization
• Risk of intellectual isolation from
each other
Divisions and Interdependencies
• Chronic disease / Infectious disease
• Clinical training / Non-clinical background
• Academia / Government / Industry / Other
• Basic research / Field epidemiology
• By disease area or exposure area