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Science
Olympiad » Disease Detectives Event
» National Event Exercises
Problem Set 1: Potential Health Hazards Associated with the Use of Cellular
Telephones
(recommended time: 25 minutes)
Molecular ionization
has been hypothesized as a cause of cellular mutations resulting in
cancer. Previously, concerns have been raised about exposure to
electromagnetic radiation from power lines. More recently, anecdotal
reports have associated cell phone use with brain cancer; however, it has
been noted that the energy in radio-frequency radiation may be
insufficient to cause molecular ionization. Cell phones transmit and
receive electromagnetic radiation at frequencies of about 1000 MHz.
- One of the first
steps used by disease detectives in an investigation like this is to
determine the study design that best investigates the hypothesis.
List two of the
most common epidemiological study designs to investigate hypotheses of
this sort. (2 points)
To investigate the
hypothesized association of cell phone usage with brain cancer, disease
detectives and other researchers studied patients in three hospitals.
They found all patients (aged 18 years and older) with primary malignant
brain tumors (i.e., the tumors originated in the brain and not elsewhere
in the body) who had been admitted to these hospitals in Boston,
Phoenix, and Pittsburgh between June 1994 and August 1998. In addition,
the investigators chose a second group of patients admitted to the same
hospitals during the same time period for conditions other than brain
tumors. They excluded from this second group, any patients with tumors
anywhere in their body. For each of the brain cancer patients studied,
the investigators also chose a patient for the second group.
- Why would the
investigators use hospitals from different regions of the country?
(1 point)
- In this
investigation disease detectives developed a standard set of
criteria for deciding whether a person should be included in the
first group of patients.
- What is the term
epidemiologists use for this standard set of criteria? (1 point)
- List the
criteria used in the study described above. (3 points)
The disease
detectives asked study participants about cellular telephone use. They
recorded calendar years of first and last use, duration of regular use
(minutes per day), usual frequency of use (at least 2 calls per week),
and which hand was usually used to hold the handset. In addition, they
collected information on educational level, family income, type of
health insurance coverage, history of medical exposure to ionizing
radiation. Some patients in both groups were too ill or too
functionally impaired to participate in the interview, or died before
the interview could be completed. For these patients, information was
obtained from other family members (proxies).
The disease
detectives enrolled 782 patients with primary brain tumors in the
study and 799 patients without tumors. (Of this second group, 197 were
admitted to the hospital for injuries.) Proxy interviews were
necessary for 12% of the patients with brain tumors and 3% of the
other group. Results from these interviews are given in Table 1 below.
Table 1:
Characteristics* of persons included in the investigation of cell
phone use and brain cancer
| Characteristic† |
Brain Cancer |
No Brain Cancer |
| Use of hand-held cell phone |
|
|
| Ever used |
308 |
358 |
| Never used |
471 |
440 |
| Average daily use |
|
|
| >15 minutes |
35 |
51 |
| <15 minutes |
103 |
117 |
| Never/rarely |
637 |
625 |
| Cumulative use |
|
|
| >500
hours |
18 |
27 |
| 101
to 499 hours |
34 |
27 |
| 13-100
hours |
47 |
58 |
| <13
hours |
39 |
55 |
| Never/rarely |
637 |
625 |
|
* Categories
within each characteristic are mutually exclusive.
†Some characteristics were not measured for all study
participants.
- Use the
information/data above from the study to determine which
characteristic(s) were most important in helping the disease
detectives to investigate the possible association between cell
phone use and brain cancer. You must show your work and include
the appropriate measures of association in Table I. Then
answer the following questions in the space provided. (11 points)
- What do
these data and your calculations permit you to conclude about
the association between cell phone use and brain cancer? (1
point)
- Explain how
you reached your conclusion. (11 points total comprised of 1
point for each correct calculation and 4 points for the
correct explanation)
- Name the
type of study design the disease detectives used. (1 point)
- What is the
term that disease detectives use for the risk estimate you
calculated? (1 point)
- Consider again
the data from the study. The ability of these data to
substantiate your conclusion may be affected by different kinds
of misclassification of patients’ exposures. List two examples
of causes of such misclassification. (2 points)
- Consider the
data from this study, your calculations and conclusions, and
your knowledge of cancer biology. Based on these considerations,
what factors might be important in further studies? List two
such factors. (2 points)
Answer Key
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