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At least 559 records · Page 31Linked to original sources
PubMed2003

Qualitative semi-parametric test for genetic associations in case-control designs under structured populations.

Recently, statistical methods have been proposed using genomic markers to control for population stratification in genetic association studies. However, these methods either have unacceptable low power when population stratification becomes strong or cannot control for population stratification well under admixture population models. In this paper, we propose a semiparametric association test to detect genetic association between a candidate marker and a qualitative trait of interest in case-control designs. The performance of the test is compared to other existing methods through simulations. The results show that our method gives correct type I error rate both under discrete population models and admixture population models, and our method is robust to the extent of the population stratification. In most of the cases we considered, our method has higher power and, in some cases, substantially higher power than that of existing methods.

Case-Control Studies↗
PubMedDate not supplied

Inter-generational occupational mobility and population heterogeneity: a statistical analysis.

"In the present paper an attempt is made to study the inter-generational occupational mobility in three types of developing villages [in India] that are heterogeneous in many socio-economic and other aspects. The specific objectives of this study are: (i) to study the overall occupational mobility of fathers-sons and to find out the predicted equilibrium structure, (ii) to find the waiting time (number of generations) that sons will stay in their fathers' occupational state before moving to other ones and (iii) to test the hypothesis of identical class structures in these three types of heterogeneous societies." The data are from a 1978 sample survey, and "the basic simple time-homogeneous Markov Chain model by Prais (1955) is employed...."

Asia↗
PubMed1994

Individualized drug utilization statistics. Analysing a population's drug use from the perspective of individual users.

The Danish retail pharmacies' drug subsidy system is completely computerized. The data are person-identifiable, making it possible to chart the population's drug use from the perspective of individual users. We decided to explore the potential of this data source and to analyse heavy drug users specifically. The analysis encompassed all 890,352 prescriptions presented by citizens of Odense in 1991. There was a total sales volume of 32 million defined daily doses consumed by 113,468 adult drug users, corresponding to 65.1% of the adult population. We found 2388 heavy drug users, defined by an annual purchase of more than 2000 defined daily doses. Heavy drug users accounted for 1.4% of the adult population and 22.9% of drug sales. They were remarkably well characterized by their main therapeutic class, which constituted a median of 47% of their drug use. A median of 97% of each heavy user's drugs were issued by one main prescriber. We conclude that heavy drug use can generally be ascribed to severe disease rather than to irresponsible prescribing. For the most important drug classes, we present various epidemiological measures of drug use, including 1-year prevalence, incidence, duration of therapy and some measures of skewness in utilization. If analysed regularly these measures can disclose subtle trends in clinical drug use that would not be evident from the wholesale figures.

Age Distribution↗
PubMedDate not supplied

The need for a statewide pediatric trauma program.

Development and maintenance of an effective regional trauma care system mandates on-going assessment of those at risk, patterns of injury and types of resources available. It is known that a significantly higher injury and traumatic death rates exists for children in a rural environment, and there is also evidence to support improved outcomes for children treated at verified trauma centers. While many still rely on practice-based statistics, we postulated that population-based statistics are much more reflective as to what is actually happening and provide crucial information on how improvements can be achieved. To test this theory, we reviewed all pediatric traumatic deaths for children 18 years old and younger from Jan. 1, 1990 to Dec. 31, 1998 at the Jon Michael Moore Trauma Center at West Virginia University, a rural pediatric trauma center. We compared this data to trauma mortality within the center's 13 county primary region from the Office of Vital Statistics. Our research revealed that mortality from pediatric trauma is higher in rural environments than in urban environments, and that population-based statistics more accurately reflect the true impact of what is actually happening in any given region. Age appears to be an important factor in determining which children are transferred to the trauma center and this may represent a critical factor in outcome.

Adolescent↗
PubMed1983

Population based pathology statistics of oesophageal carcinoma.

The frequency of oesophageal carcinoma among autopsies performed in the Institute of Pathology in Heidelberg between 1900 and 1979 is estimated and compared with the findings of the patho-anatomically based Regional Cancer Registry of North Baden. The autopsy data suggest that there is no increase in the percentage of oesophageal carcinoma in the area of Heidelberg during the period considered. The average age of oesophageal carcinoma patients at death remained nearly unchanged during the study period, while the average age of death for all autopsies showed a steep increase. In a retrospective study of the registry data, oesophageal carcinoma patients showed a higher percentage of alcohol consumers and heavy smokers over patients with stomach, colon, and rectal cancer. The retrospective study of clinical findings further revealed liver cirrhosis in 8%. This was not documented in patients with other gastro-intestinal carcinomas. The results obtained suggest that patho-anatomical data may be useful for checking the applicability of results obtained elsewhere.

Adult↗
PubMed1999

Statistical evaluation of population data for calculation of radioactive material transport accident risks.

Calculation of accident dose-risk estimates with the RADTRAN code requires input data describing the population likely to be affected by the plume of radioactive material (RAM) released in a hypothetical transportation accident. In the existing model, population densities within 1/2 mile (0.8 km) of the route centerline are tabulated in three ranges (Rural, Suburban, and Urban). These population densities may be of questionable validity since the plume in the RADTRAN analysis is assumed to extend out to 120 km from the hypothetical accident site. We present a GIS-based population model which accounts for the actual distribution of population under a potential plume, and compare accident-risk estimates based on the resulting population densities with those based on the existing model. Results for individual points along a route differ greatly, but the cumulative accident risks for a sample route of a few hundred kilometers are found to be comparable, if not identical. We conclude, therefore, that for estimation of aggregate accident risks over typical routes of several hundred kilometers, the existing, simpler RADTRAN model is sufficiently detailed and accurate.

Accidents, Traffic↗
PubMed2002

Sciatic nerve variations in some studies on the Polish population and its statistical significance.

The purpose of the study was to describe and analyse sciatic nerve variation in a relatively small, yet statistically significant, group. Consequently, a comparison of described variation to that known from former studies was performed. Additionally, we estimated the minimum group necessary for a statistical confirmation of hypothetical differences in sciatic nerve topography between the studies.

Female↗
PubMedDate not supplied

Annual and sub-annual rhythms in human conception rates. I. Effective correction and use of public record LMP dates.

Most studies of rhythms in human conception rates have used monthly total births back-dated 9 months. Such data are of little use for studying any pattern less than a few months in length. Even at that level, they are poor material for studying the possibility of altered conception rhythms in anomalous births. The high frequency of premature delivery in such births makes a simple 9-month offset simplistic and misleading. Dates of last normal menses (LMP) provide appropriate detail, but have generally been dismissed as unreliable. In a large public birth record dataset, we have identified a clear artifact of poor LMP recall, highly correlated with passage of time between conception and onset of prenatal care. The majority of the variation in daily LMP counts due to this recall artifact can be corrected statistically to yield population data suitable to more detailed analyses.

Female↗
PubMed1986

Statistics of natural populations. III. Sequential sampling plans for the estimation of gene frequencies.

In previous work several models have been developed for genetic surveys of natural populations. Parents of unknown genotype are collected from a natural population, polymorphic at a single genetic locus. From each of these N cryptic parents a number of offspring are identified for their genotype. Our problem is to select an efficient offspring sampling plan for estimating the frequency of an allele in the cryptic adult population based on the N family profiles of juvenile genotypes. A criterion called the information per unit cost of observation is introduced to evaluate sequential sampling plans, in which the number of offspring per family examined is random. Some simple, practical schemes for stopping the sampling of offspring from a collected parent are introduced; one example is stopping when: (i) the offspring are definitive about the parental genotype(s) for the first time; (ii) a fixed number of one genotype only is seen; or (iii) a fixed maximum feasible number of offspring have been genotyped. This sampling scheme is recommended. For each sampling scheme, the best linear unbiased estimator and the sequential maximum likelihood estimator of the allele frequency are characterized. From the moments of these estimators, it is then possible to tabulate efficient sequential sampling plans, which are better (in the sense of information per unit cost), just as simple, and less costly than corresponding fixed sampling plans in use.

Alleles↗