Exercise 6 identifying analytic research types. . Read the following research reports and abstracts
carefully and identify whether the research is descriptive, cross-sectional, experimental, cohort or
case control.
1.
Effect of habitual knuckle cracking on hand function
Jorge Castellanos, David Axelrod
Abstract
The relation of habitual knuckle cracking to osteoarthrosis with functional impairment of the hand
has long been considered an old wives' tale without experimental support. The mechanical sequelae
of knuckle cracking have been shown to produce the rapid release of energy in the form of sudden
vibratory energy, much like the forces responsible for the destruction of hydraulic blades and ship
propellers. To investigate the relation of habitual knuckle cracking to hand function 300
consecutive patients aged 45 years or above and without evidence of neuromuscular, inflammatory,
or malignant disease were evaluated for the presence of habitual knuckle cracking and hand
arthritis/dysfunction. The age and sex distribution of the patients (74 habitual knuckle crackers, 226
non-knuckle crackers) was similar. There was no increased preponderance of arthritis of the hand in
either group; however, habitual knuckle crackers were more likely to have hand swelling and lower
grip strength. Habitual knuckle cracking was associated with manual labour, biting of the nails,
smoking, and drinking alcohol. It is concluded that habitual knuckle cracking results in functional
hand impairment.
Not experimental because the researcher is not administering the treatment. The participants (300
consecutive patients aged 45 years and over – i.e. it is a convenience sample as the 300 were chosen
consecutively as they came into a doctor’s office. The type of doctor’s office is not specified.)
Not cohort prospective as the patients were not followed over time, and not case control as the
researcher did not start with a group who had arthritis.
Exposure: habitual knuckle cracking;
Outcome (primary): arthritis (secondary): hand swelling, grip strength
Age and sex were treated as possible confounding variables.
It seems that there are 2 possibilites: Cross-sectional since the patients are asked 2 questions: Are
you a habitual knuckle cracker? Do you have arthritis? The focus is on the now! Retrospective
cohort seems possible since the exposure to knuckle cracking happened over time in the past.
Cross-sectional is a better answer as there does not seem to be any attempt to assess the length of
time nor the ‘intensity’ of knuckle cracking – the exposure is habitual knuckle cracking.
2. Crack Research: Good news about knuckle cracking
The latest physical anthropology research indicates that the human evolutionary line never went through a knucklewalking phase. Be that as it may, we definitely entered, and have yet to exit, a knuckle-cracking phase. I would run out
of knuckles (including those on my feet) trying to count how many musicians wouldn’t dream of playing a simple scale
without throwing off a xylophonelike riff on their knuckles first. But despite the popularity of this practice, most known
knuckle crackers have probably been told by some expert—whose advice very likely began, “I’m not a doctor, but
...”—that the behavior would lead to arthritis. One M.D. convincingly put that amateur argument to rest with a study
published back in 1998 in the journal Arthritis & Rheumatism entitled “Does Knuckle Cracking Lead to Arthritis of the
Fingers?” The work of sole author Donald Unger was back in the news in early October when he was honored as the
recipient of this year’s Ig Nobel Prize in Medicine.
The Igs, for the uninitiated, are presented annually on the eve of the real Nobel Prizes by the organization Improbable
Research for “achievements that first make people laugh, and then make them think.” In Unger’s case, I thought about
whether his protocol might be evidence that he is obsessive-compulsive. From his publication: “For 50 years, the author
cracked the knuckles of his left hand at least twice a day, leaving those on the right as a control. Thus, the knuckles on
the left were cracked at least 36,500 times, while those on the right cracked rarely and spontaneously.” Unger
undertook his self and righteous research because, as he wrote, “During the author’s childhood, various renowned
authorities (his mother, several aunts and, later, his mother-in-law [personal communication]) informed him that
cracking his knuckles would lead
to arthritis of the fingers.” He thus used a half-century “to test the accuracy of this hypothesis,” during which he could
cleverly tell any unsolicited advice givers that the results weren’t in yet. Finally, after five decades, Unger analyzed his
data set: “There was no arthritis in either hand, and no apparent differences between the two hands.” He concluded that
“there is no apparent relationship between knuckle cracking and the subsequent development of arthritis of the fingers.”
Evidence for whether the doctor himself was cracked may be that he traveled all the way from his California home to
Harvard University to pick up his Ig Nobel Prize in person. Actually other scholarly studies of the phenomenon had
been done. Responding to the Unger paper, Robert Swezey, M.D., wrote to the journal to report that his own 1975
study—co-authored by his then 12-year-old son in an apparent attempt to get the kid’s grandma to stop the kvetching
over the cracking—also found no crack case for arthritis. Swezey further consulted statistician , who noted that “it
appears that the [Unger] study was not blinded. Blinding would only be possible if the investigator didn’t know left
from right. This is not likely since studies indicate that only 31 percent of primary care physicians don’t know left from
right.” The knuckle kerfuffle reminded me that bone development expert got dragged into this field a few years back
when his son’s fourth grade class asked him if cracking was bad for you. He challenged them to come up with ways to
find out while he searched the medical literature. “One kid said that we could divide the room in half,” he recalled, “and
some of us could really crack our knuckles a lot and the others couldn’t, and we could see whether we end up with
arthritis—an intervention experiment. I said that this was a great idea. The only problem was that it might take 20
years.” Or even 50.
Experimental because the researcher is administering the treatment. The treatment in this case is
knuckle cracking. The participants (i.e. the unit of analysis) is the hands. n = 2, with only one
participant (hand) in each of the treatment and control groups. This is kind of weird as we would
expect there to be more than 1 participant in each group.
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3. Coffee consumption unrelated to alertness
2 June 2010
The stimulatory effects of caffeine may be nothing more than an illusion according to new BBSRC-funded
research, which shows there is no real benefit to be gained from the habitual morning cup of coffee.
Tests on 379 individuals who abstained from caffeine for 16 hours before being given either caffeine or a
placebo and then tested for a range of responses showed little variance in levels of alertness.
The study, published online in the journal of Neuropsychopharmacology, reports that frequent coffee
drinkers develop a tolerance to both the anxiety-producing effects and the stimulatory effects of caffeine.
While frequent consumers may feel alerted by coffee, evidence suggests that this is actually merely the
reversal of the fatiguing effects of acute caffeine withdrawal. And given the increased propensity to anxiety
and raised blood pressure induced by caffeine consumption, there is no net benefit to be gained.
Peter Rogers, from the University of Bristol's Department of Experimental Psychology and one of the lead
authors of the study, said: "Our study shows that we don't gain an advantage from consuming caffeine although we feel alerted by it, this is caffeine just bringing us back to normal. On the other hand, while
caffeine can increase anxiety, tolerance means that for most caffeine consumers this effect is negligible."
Approximately half of the participants were non/low caffeine consumers and the other half were
medium/high caffeine consumers. All were asked to rate their personal levels of anxiety, alertness and
headache before and after being given either the caffeine or the placebo. They were also asked to carry out
a series of computer tasks to test for their levels of memory, attentiveness and vigilance.
The medium/high caffeine consumers who received the placebo reported a decrease in alertness and an
increase in headache, neither of which were reported by those who received caffeine. However, their postcaffeine levels of alertness were no higher than the non/low consumers who received a placebo,
suggesting caffeine only brings coffee drinkers back up to 'normal'.
Experimental because the researcher is administering the treatment. The treatment in this case is
caffeine (control is a placebo).
Exposure: caffeine (vs placebo)
Outcome (primary): range of responses that measured levels of alertness
Outcomes (secondary) anxiety, feeling of alertness.
There is a tricky part to this study too as previous levels of caffeine consumption are mentioned
(e.g. low/medium/high caffeine consumers). This may make it feel like a cohort study. However,
the previous levels of caffeine consumption are treated as a confounding variable.
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4. Randomised prostate cancer screening trial: 20 year follow-up
Gabriel Sandblom, associate professor1, Eberhard Varenhorst, professor2, Johan Rosell, statistician3, Owe Löfman,
professor4, Per Carlsson, professor5 Accepted 24 December 2010 BMJ
ABSTRACT
Objective: To assess whether screening for prostate cancer reduces prostate cancer specific mortality.
Design: Population based randomised controlled trial.
Setting: Department of Urology, Norrköping, and theSouth-East Region Prostate Cancer Register.
Participants: All men aged 50-69 in the city of Norrköping, Sweden, identified in 1987 in the
National Population Register (n=9026).
Intervention: From the study population, 1494 men were randomly allocated to be screened by
including every sixth man from a list of dates of birth. These men were invited to be screened every
third year from 1987 to 1996. On the first two occasions screening was done by digital rectal
examination only. From 1993, this was combined with prostate specific antigen testing, with 4 μg/L
as cut off. On the fourth occasion (1996), only men aged 69 or under at the time of the investigation
were invited.
Main outcome measures: Data on tumour stage, grade, and treatment from the South East Region
Prostate Cancer Register. Prostate cancer specific mortality up to 31 December 2008.
Results: In the four screenings from 1987 to 1996 attendance was 1161/1492 (78%), 957/1363
(70%), 895/1210 (74%), and 446/606 (74%), respectively. There were 85 cases (5.7%) of prostate
cancer diagnosed in the screened group and 292 (3.9%) in the control group. The risk ratio for death
from prostate cancer in the screening group was 1.16 (95% confidence interval 0.78 to 1.73). In a
Cox proportional hazard analysis comparing prostate cancer specific survival in the control group
with that in the screened group, the hazard ratio for death from prostate cancer was 1.23 (0.94 to
1.62; P=0.13). After adjustment for age at start of the study, the hazard ratio was 1.58 (1.06 to 2.36;
P=0.024).
Conclusions After 20 years of follow-up the rate of death from prostate cancer did not differ
significantly between men in the screening group and those in the control group.
Experimental because the researcher is administering the treatment. The treatment in this case is
screening for prostate cancer.
Exposure: screening for prostate cancer (vs non-screening)
Outcome (primary): death from prostate cancer. Outcome (secondary): diagnosis of prostate cancer
This one is pretty straightforward, except that it seems weird to have screening as a ‘treatment’.
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5. Daily Candy Consumption in Children Linked to Violence in Adulthood
Deborah Brauser
October 5, 2009 — Excessive consumption of confectionery (sweets/chocolates) during childhood can increase the
likelihood of adult aggression, according to results from a large cohort study published in the October issue of the
British Journal of Psychiatry.
In this study, "children who ate confectionery daily at age 10 years were significantly more likely to have been
convicted for violence at age 34 years," write Simon C. Moore, PhD, and colleagues from the Violence and Society
Research Group and Applied Clinical Research and Public Health in the School of Dentistry at Cardiff University in
Wales.
Although past studies have shown a causal effect between diet and behavioral problems, including aggression, this is
the first study to look at the long-term effects of childhood diet on adult violence, report the study authors.
In addition, "we think that kids who demand candy every day do not learn to delay gratification, which some think is a
feature of violent individuals generally," Dr. Simon told Medscape Psychiatry.
"The main takeaway for clinicians is that small changes early in life can make a profound difference in childhood," he
added.
Background
"We've been researching offending behavior in youngsters for a long time and we've found that problem behavior
seems to be associated with impulsive risk taking," explained Dr. Simon. "We also noticed that the diets of these
youngsters were pretty poor. Coupled with other research suggesting a link between diet and behavior, we decided to
look at data to see whether confectionery consumption was linked to adult violence."
The investigators examined data from 17,415 participants in the British Cohort Study born between April 5 and April
11, 1970 in the United Kingdom. That cohort study collected data on health, education, and social and economic status
from respondents at varying stages from age 5 to 42 years.
Consistent Association Found Between Confectionery and Violence
Results showed that 69.7% of the study participants who were violent by the age of 34 reported that they ate
confectionery nearly every day during childhood, whereas only 42% of those who were nonviolent did.
Other significant relations between control variables and violence included the child's sex (male) and the parents'
attitude toward parenting. Access to motorized transport at 34 years was found to protect against adult violence,
whereas living in a rural area at 34 years increased the risk for violence.
"We found the main result quite surprising and interpret it as perhaps evidence that it is the way that confectionery is
given to kids rather than the candy itself," said Dr. Simon.
He explained that a plausible mechanism for the link is that persistently using confectionery to control childhood
behavior might prevent children from learning to defer gratification, which can lead to more impulsive behaviors.
These are both biases that are strongly associated with delinquency.
"Irrespective of the causal mechanism, which warrants further attention, targeting resources at improving childhood diet
may improve health and reduce aggression," write the study authors.
"The next step is to better understand how social, psychological, and consumption factors interact to produce problem
behavior," concluded Dr. Simon.
This one is tricky because the data comes from a prospective cohort study, but the researchers are using the data set as
for secondary purposes. Once that is clear, it is easy to dismiss all except retrospective cohort and case control. Your
choice depends on how you interpret the data collection. You would choose retrospective cohort if you don’t see any
indication that the researchers started with a group of individuals that were ‘violent’ and then compared their exposure
to candy to a group of ‘non-violent’ controls. There is no indication that that was done, which means that they may
have started with the whole population and then looked for ‘violence’ and candy exposure – i.e. retrospective cohort.
However, the way the way the results are reported (% of candy eaters in ‘violent’ vs ‘non-violent’) would make me
choose case control.
In reading the full study it is clear that this was in fact a retrospective cohort study as the researchers simply looked for
the outcome in all respondents and did not start with a group of incarcerated individuals.
This one is very tricky .
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6. Three-second distraction doubles work errors
Posted By Andy Henion-Michigan State On January 8, 2013 @ 11:29 am In Top Stories | 2
Comments
MICHIGAN STATE (US) — Even tiny interruptions can derail your train of thought and increase mistakes, new
research shows.
Short interruptions—such as the few seconds it takes to silence that buzzing smartphone— have a surprisingly large
effect on one’s ability to accurately complete a task, according to new research. The study, in which 300 people
performed a sequence-based procedure on a computer, found that interruptions of about three seconds doubled the error
rate.
Brief interruptions are ubiquitous in today’s society, from text messages to a work colleague poking his head in the
door and interrupting an important conversation. But the ensuing errors can be disastrous for professionals such as
airplane mechanics and emergency room doctors, says Erik Altmann, lead researcher on the study and associate
professor of psychology at Michigan State University.
“What this means is that our health and safety is, on some level, contingent on whether the people looking after it have
been interrupted,” says Altmann.
The study, published in Journal of Experimental Psychology: General [1], is one of the first to examine brief
interruptions of relatively difficult tasks. Study participants were asked to perform a series of tasks in order, such as
identifying with a keystroke whether a letter was closer to the start or the end of the alphabet. Even without
interruptions a small number of errors in sequence were made.
Sometimes participants were interrupted and told to type two letters—which took 2.8 seconds—before returning to the
task. When this happened, they were twice as likely to mess up the sequence. Altmann says he was surprised that such
short interruptions had a large effect. The interruptions lasted no longer than each step of the main task, he noted, so the
time factor likely wasn’t the cause of the errors. “So why did the error rate go up?” Altmann asks. “The answer is that
the participants had to shift their attention from one task to another. Even momentary interruptions can seem
jarring when they occur during a process that takes considerable thought.” One potential solution, particularly when
errors would be costly, is to design an environment that protects against interruptions. “So before you enter this critical
phase: All cell phones off at the very least,” Altmann says.
Gregory Trafton of the Naval Research Laboratory and Zach Hambrick of Michigan State are
co-authors of the study, which was funded by the US Navy
This one is tricky because the unit of analysis is not the same as the participants. 300 participants
are ‘people’, but the unit of analysis (the object being studied) was the set of tasks that they were
asked to perform. The treatment that was administered (to the tasks) was an interruption (or no
interruption). Imagine the data set. It will include every single task that the 300 individuals were
asked to perform. If they performed 100 tasks each then there will be 30,000 cases. For each case
the researchers coded whether the task was interrupted and whether an error was made (yes/no)
Given that the interruptions (yes or no) were controlled/administered by the researcher this one is
clearly an experiment.
Exposure: interruption (yes/no)
Outome: error (yes/no)
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7. Literacy education as treatment for depression in patients with limited
literacy and depression: a randomized controlled trial.
Weiss, Barry D, Francis, Laurie; Senf, Janet H; Heist, Kim; Hargraves, Rie
BACKGROUND: Individuals with limited literacy and those with depression share many characteristics, including low
self-esteem, feelings of worthlessness, and shame.
OBJECTIVE: To determine whether literacy education, provided along with standard depression treatment to adults
with depression and limited literacy, would result in greater improvement in depression than would standard depression
treatment alone.
DESIGN: Randomized clinical trial with patients assigned either to an intervention group that received standard
depression treatment plus literacy education, or a control group that received only standard depression treatment.
PARTICIPANTS: Seventy adult patients of a community health center who tested positive for depression using the 9question Patient Health Questionnaire (PHQ-9) and had limited literacy based on the Rapid Estimate of Adult Literacy
in Medicine (REALM).
MEASUREMENTS: Depression severity was assessed with PHQ-9 scores at baseline and at 3 follow-up evaluations
that took place up to 1 year after study enrollment. Changes in PHQ-9 scores between baseline and follow-up
evaluations were compared between the intervention and control groups.
RESULTS: The median PHQ-9 scores were similar in both the intervention and control groups at baseline (12.5 and 14,
respectively). Nine-question Patient Health Questionnaire scores improved in both groups, but the improvement was
significantly larger in the intervention group. The final follow-up PHQ-9 scores declined to 6 in the intervention group
but only to 10 in the control group.
CONCLUSIONS: There may be benefit to assessing the literacy skills of patients who are depressed, and
recommending that patients with both depression and limited literacy consider enrolling in adult education classes
as an adjuvant treatment for depression.
Weiss, B. D., Francis, L., Senf, J. H., Heist, K., & Hargraves, R. (2006). Literacy education as treatment for depression
in patients with limited literacy and depression: a randomized controlled trial. Journal of general internal
medicine, 21(8), 823–8. doi:10.1111/j.1525-1497.2006.00531.x
Experiment because the researcher is administering a treatment (literacy program). This one is pretty
straightforward. You will receive the full-text of this study for further analysis.
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