Debanne SM, Bielefeld RA, Cauthen G, Daniel TM, Rowland
DY. A Multivariate Markov Chain Model of Tuberculosis: Forecasts for
the United States. Emerging Infectious Diseases 2000;6(2):30-39.
ABSTRACT
We have developed a computer-implemented, multivariate Markov chain
model to project tuberculosis incidence in the United States from
1980 to 2010 in disaggregated demographic groups. Uncertainty in model
parameters and in the projections is represented using fuzzy numbers.
Projections are made under the assumption that tuberculosis control
measures currently in place will remain unchanged for the duration
of the projection period. The projections of the model demonstrate
an intermediate increase in national tuberculosis incidence similar
to that which actually occurred, followed by continuing decline. The
rate of decline is strongly dependent on geographic, racial, and ethnic
characteristics. The model predicts that the rate of decline in the
number of cases in Hispanics will be less than those for white non-Hispanics
and for black non-Hispanics, a prediction supported by the most recent
data.
Debanne SM, Rowland DY. Statistical Certification
of Eradication of Poliomyelitis in the Americas. Mathematical Biosciences
1998;150:83-103.
ABSTRACT
The last confirmed case of paralytic poliomyelitis due to indigenous
wild poliovirus in the Americas occurred in Peru in 1991. In 1994
the International Commission on Polio Eradication of the Pan American
Health Organization (PAHO) deemed eradication of polio from the area
to have occurred, based on its strategic efforts and the observed
results. A mathematical model, based on fluctuation theory, is presented
here which relates the time elapsed since that last detected case
of paralytic poliomyelitis caused by wild poliovirus to the probability
that the transmission of indigenous wild poliovirus has been stopped.
The appropriateness of applying the model to various geographical
areas of the Americas is investigated using data about the occurrence
of confirmed cases of polio since 1984, the time of the eradication
initiative adopted by PAHO.
The model suggests that if four years have elapsed since the last
reported confirmed case of polio caused by wild poliovirus, and no
other confirmed cases have been identified, the probability of undetected
indigenous wild poliovirus transmission is less than 5%. An important
assumption is that the eradication strategy implemented by PAHO has
yielded steady improvements.
A consequence of this approach is that the annual probabilities of
persistence given by the model are conservative, in the sense of being
higher than the true, but unknown a priori probabilities, and more
so with each passing year. It is thus seen that the model results
are compatible with the conclusion reached by PAHO in 1994. The model
takes into account the intensity of surveillance of each country in
the region, measured by the corresponding rates of acute flaccid paralysis.
Because importations of wild poliovirus may occur from other regions
of the world, surveillance efforts are being maintained in the Americas
until global eradication has been achieved.
Debanne SM, Riedel T, Cleves
M, Rowland DY. Association Between Alzheimer's Disease and Smoking:
The Case for Sibling Controls. To appear July 2000, J Am Geriatrics
Soc.
ABSTRACT
OBJECTIVES: To study the association between cigarette smoking and
Alzheimer’s Disease (AD). DESIGN: Intra-family case-control, with
sibling controls and variable number of controls per case. SETTING:
AD cases were identified through the Research Registry of the University
Hospitals of Cleveland/Case Western Reserve University Alzheimer Center.
PARTICIPANTS: Study subjects were 86 probable AD cases (index cases),
and all their full siblings, alive or dead, who had attained the age
of 50, for a total of 238 subjects. MEASUREMENTS: For each individual,
exposure was ascertained with a questionnaire answered by multiple
informants. Cognitive status of siblings of the AD cases (impaired
or intact) was ascertained by telephone, using validated instruments.
Diagnosis of dementia in cognitively impaired siblings of index cases
was not attempted. RESULTS: Chi-square analysis tested for departure
from a random distribution of disease across smokers and non-smokers
within families. No significant departure was found utilizing all
families (p > 0.40), nor utilizing those families where only the index
case was affected (p > 0.90). Conditional logistic regression evaluated
the association within families, controlling for age, sex and education.
Analyses both included and excluded secondary cases of cognitive impairment.
No association was found between smoking and disease (OR = 1.26, 95
percent confidence interval 0.66-2.42, and OR = 1.42, 95 percent confidence
interval 0.69-2.89, respectively). CONCLUSION: No significant association
between smoking and cognitive status was found. Further, those analyses
based on the comparison of AD cases to their unaffected siblings suggest
that smoking does not decrease the risk of AD.
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