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PubMed1995

Life expectancy at age 60--epidemiologic scenarios assuming delayed mortality for selected causes of death.

"The present analysis offers a projection of life expectancy at advanced ages in Austria for the year 2010. To estimate the gains in life expectancy the Simultaneous Multiple Cause-Delay (SIMCAD) method is used. This model takes into account the epidemiological concept of an additional delay in the onset of particular chronic-degenerative diseases. While the results of the SIMCAD method vary only slightly on the whole from the official projection of life expectancy at age 60, the similarity between the two projections decreases steadily with increasing age. The SIMCAD model predicts higher gains in life expectancy for the oldest age-groups of the population than do the official statistics." (SUMMARY IN FRE)

Adult↗

PubMed2003

Breastfeeding and the risk of hospitalization for respiratory disease in infancy: a meta-analysis.

OBJECTIVE: To examine breastfeeding and the risk of hospitalization for lower respiratory tract disease in healthy full-term infants with access to modern medical care. DATA SOURCES: MEDLINE, personal communication with researchers, the OVID databases, Dissertation Abstracts Online, and BIOSIS. STUDY SELECTION: The titles, abstracts, and text of studies from developed countries were explored for breastfeeding exposure measures and lower respiratory tract disease hospitalization rates. For summary statistics, we required 3 inclusion criteria: (1) a feeding contrast of a minimum of 2 months of exclusive breastfeeding (no formula supplementation) vs no breastfeeding and (2) study populations that excluded sick, low birth weight or premature infants and (3) reflected affluent regions; 27% of studies met these criteria. DATA EXTRACTION: We abstracted data from all relevant reports. DATA SYNTHESIS: Data from all primary material (33 studies) indicated a protective association between breastfeeding and the risk of respiratory disease hospitalization. Nine studies met all inclusion criteria, and 7 cohort studies were pooled. The feeding contrasts in these 7 studies were 4 or more months of exclusive breastfeeding vs no breastfeeding. The summary relative risk (95% confidence interval) was 0.28 (0.14-0.54), using a random-effects model. This effect remained stable and statistically significant after adjusting for the effects of smoking or socioeconomic status. CONCLUSION: Among generally healthy infants in developed nations, more than a tripling in severe respiratory tract illnesses resulting in hospitalizations was noted for infants who were not breastfed compared with those who were exclusively breastfed for 4 months.

Breast Feeding↗

PubMed1992

Indoor 222Rn concentrations in a probability sample of 43,000 houses across 30 states.

The U.S. Environmental Protection Agency has assisted 30 of the 48 conterminous states in completing statistically designed surveys of indoor 222Rn over the past 4 y. In all states, the lowest livable level of 43,054 randomly selected houses was tested using charcoal canisters exposed for 48 h. The sampled population included owner-occupied ground-level houses having listed telephone numbers. Summary statistics along with the percentage of houses exceeding various concentration levels are given by state and over all states for houses with basements, for houses without basements, and for all houses. As expected, 222Rn concentration varies widely from one state to another and, in every state, basement houses exhibit higher concentrations than nonbasement houses. The lognormal distribution is shown to be a good approximation to the distribution of screening measurements over the 30-state area. There is, however, some evidence that the lognormal distribution underestimates, by a narrow margin, the upper tail of the observed distribution of basement measurements.

Air Pollutants, Radioactive↗

PubMed2000

The effects of visual input on postural control mechanisms: an analysis of center-of-pressure trajectories using the auto-regressive model.

New measures to characterize center-of-pressure (COP) trajectories during quiet standing were proposed and then utilized to investigate changes in postural control with respect to visual input. Eleven healthy male subjects (aged 20-27 years) were included in this study. An instrumented force platform was used to measure the time-varying displacements of the COP under each subject's feet during quiet standing. The subjects were tested under eyes-open and eyes-closed conditions. The COP time series were separately analyzed for the medio-lateral and antero-posterior directions. The proposed measures were obtained from the parameter estimation of auto-regressive (AR) models. The percentage contributions and geometrical moment of AR coefficients showed statistically significant differences between vision conditions. The present COP displacements under the eyes-open condition showed higher correlation with the past COP displacements at longer lag times, when compared to the eyes-closed condition. In contrast, no significant differences between vision conditions were found for conventional summary statistics, e.g., the total length of the COP path. These results suggest that the AR parameters are useful for the evaluation of postural stability and balance function, even for healthy young individuals. The role of visual input in the postural control system and implications of the findings were discussed.

Adult↗

PubMed2026

Systematic common and rare variant association testing in 392,030 whole genomes in All of Us.

Large-scale genome-wide association studies (GWAS) and rare variant association studies (RVAS) from population biobanks provide valuable resources for gene discovery in complex human traits. We present an analysis of the All of Us Research Program v8 release, which includes whole genome sequencing data and harmonized phenotypic information of 392,030 participants after quality control, enabling a unified investigation of rare and common variants across a spectrum of human traits and diseases. We build an extensive phenome- and genome-wide ("All by All") computational framework to perform GWAS and RVAS on 3,602 phenotypes and identify 49,863 approximately independent, high-quality single-variant and gene-level associations. Meta-analyses of All of Us and UK Biobank, with sample sizes as large as 786,871 participants, further enhance statistical power and find 193 pLoF gene-phenotype associations that are not significant in either cohort alone, including 22 associations not highlighted by previous studies. We also present a public interactive browser that integrates association results for common and rare variants to facilitate interpretation and rapid querying of summary statistics, along with supporting documentation, and a Featured Workspace in the All of Us Researcher Workbench. Our framework will apply to iterative data releases as All of Us grows, empowering researchers worldwide to uncover insights into the functional effects of genetic components on complex traits and diseases.

Journal Article↗

PubMed2005

Morphological characterization of point patterns.

A triplet of function s for the statistical characterization of planar point patterns is introduced. They are related to the integral-geometric quantities area, boundary length and Euler number of patterns of discs centred at the given points. These functions are able to give information on the distribution of a given point pattern which the traditional summary statistics of point process theory do not offer and so can lead to an improved statistical description. The paper describes the statistical estimation of the new characteristics. Some examples illustrate their application in the exploratory analysis of point patterns of tree positions in forests, in comparison to results obtained by means of second-order and distance characteristics.

Agriculture↗

PubMed2006

Cross-over trials in Statistics in Medicine: the first '25' years.

Papers on cross-over trials that have appeared in the first 25 years of Statistics in Medicine are reviewed. Papers on bioequivalence are also considered. After a brief statistical summary, individual papers are discussed under seven headings: 1. The two-stage analysis of AB/BA trials, 2. Baselines, 3. Binary and categorical data, 4. Survival data, 5. Modelling carry-over, 6. Bioequivalence and 7. Components of variation. Finally, a brief assessment of the importance in this field of Statistics in Medicine is given.

Cross-Over Studies↗

PubMed2006

Head circumference from birth to age 48 months for infants in Sweden.

AIM: To describe the development of head circumference, from birth to age 48 mo, of infants in Sweden. METHODS: Every infant born on the 15th of any month in the 1981 birth cohort, living in Sweden as of 31 December 1989, was studied from birth to age 48 mo (n=3158). By collecting data from child healthcare records and then analysing these data using piecewise linear regression, means and other statistics were produced for every age. Data were analysed for all and with exclusions for low birthweight and those born outside Sweden. RESULTS: From the sample of 3158, data for 3107 infants were collected, making the percentage of missing individuals 1.6%; thus, non-response bias is minimized and high national representativeness is achieved. Summary statistics for head circumference are presented. Comparisons are made to international reference materials, and to previous and current Swedish reference curves. CONCLUSION: For the first time in Sweden, and without selection bias, means and distribution of head circumference measurements are documented longitudinally for a nationally representative sample of infants.

Child, Preschool↗

PubMed2000

Ovulation suppression for endometriosis.

BACKGROUND: Although the etiology of endometriosis is unknown, several theories exist, the most popular of which is retrograde menstruation. As endometriosis can only be diagnosed by laparoscopy, neither the incidence (annual occurrence) nor the prevalence (proportion of the population affected) of endometriosis is known. The association between endometriosis and infertility isn't clear in Stage I (minimal) and Stage II (mild) endometriosis. Endometriosis appears to be an estrogen dependent condition. At the time of menopause, most endometriosis becomes quiescent. This hormonal dependency prompted researchers to seek agents which would suppress ovarian activity. OBJECTIVES: To determine effectiveness of a) ovulation suppression with danazol, medroxy progesterone acetate, gestrinone, combined oral contraceptive pills and GnRH analogues versus placebo or no treatment and b) any of the above agents versus danazol, for the treatment of endometriosis explained infertility in terms of clinical pregnancy rate. SEARCH STRATEGY: The Cochrane Subfertility Review Group specialised register of controlled trials was searched. SELECTION CRITERIA: Four RCTs with five treatment arms compared an ovulation suppression agent with placebo or no treatment. Eight trials were identified comparing a suppressive agent with danazol. DATA COLLECTION AND ANALYSIS DATA EXTRACTION: A diverse search strategy was employed, including hand-search of 43 core journals from 1966 to the present, bibliographies of relevant trials, MEDLINE database, abstracts from North American and European meetings and contact with authors of relevant papers. Relevant data were extracted independently by two reviewers using the standardised data extraction sheet. Validity was assessed in terms of method of randomisation, completeness of follow-up, presence or absence of crossover and co-intervention. DATA SYNTHESIS: 2x2 tables were generated for all relevant outcomes. Odds ratios were generated using the Peto modified Mantel-Haenszel technique. Statistical heterogeneity was assessed using x2. MAIN RESULTS: The common odds ratio for pregnancy following ovulation suppression versus placebo or no treatment was 0.83 (95% CI 0.5-1.39). These data were statistically homogeneous although clinical heterogeneity was present. Their consistency in showing no treatment benefit suggests that this group of interventions is ineffective. Common odds ratio for pregnancy following all agents versus danazol was 1.20 (95% CI 0. 85-1.68). Again these data were homogeneous and suggest no significant treatment benefit in terms of pregnancy rate. REVIEWER'S CONCLUSIONS: Given the significant period of amenorrhea associated with ovulation suppression, the lack of treatment benefit demonstrated and the adverse effects commonly associated with these treatments, ovulation suppression cannot be recommended as a standard therapy for endometriosis-associated infertility.

Danazol↗

PubMed1999

Statistical method to evaluate management strategies to decrease variability in operating room utilization: application of linear statistical modeling and Monte Carlo simulation to operating room management.

BACKGROUND: Operating room (OR) managers seeking to maximize labor productivity in their OR suite may attempt to reduce day-today variability in hours of OR time for which there are staff but for which there are no cases ("underutilized time"). The authors developed a method to analyze data from surgical services information systems to evaluate which management interventions can most effectively decrease variability in underutilized time. METHODS: The method uses seven summary statistics of daily workload in a surgical suite: daily allocated hours of OR time, estimated hours of elective cases, actual hours of elective cases, estimated hours of add-on cases, actual hours of add-on cases, hours of turnover time, and hours of underutilized time. Simultaneous linear statistical equations (a structural equation model) specify the relationship among these variables. Estimated coefficients are used in Monte Carlo simulations. RESULTS: The authors applied the analysis they developed to two OR suites: a tertiary care hospital's suite and an ambulatory surgery center. At both suites, the most effective strategy to decrease variability in underutilized OR time was to choose optimally the day on which to do each elective case so as to best fill the allocated hours. Eliminating all (1) errors in predicting how long elective or add-on cases would last, (2) variability in turnover or delays between cases, or (3) day-to-day variation in hours of add-on cases would have a small effect. CONCLUSIONS: This method can be used for decision support to determine how to decrease variability in underutilized OR time.

Humans↗

PubMed2006

Multifocal versus monofocal intraocular lenses after cataract extraction.

BACKGROUND: Good unaided distance visual acuity is now a realistic expectation following cataract surgery and intraocular lens (IOL) implantation. Near vision however still requires additional refractive power usually in the form of reading glasses. Multiple optic (multifocal) IOLs are available which claim to allow good vision at a range of distances. It is unclear whether this benefit outweighs the optical compromises inherent in multifocal IOLs. OBJECTIVES: The objective of this review was to assess the effects of multifocal IOLs, including effects on visual acuity, subjective visual satisfaction, spectacle dependence, glare and contrast sensitivity, compared to standard monofocal lenses. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which includes the Eyes and Vision Group Trials Register) on The Cochrane Library (2006, Issue 3), MEDLINE (1966 to July 2006), EMBASE (1980 to July 2006), NRR (2006, Issue 3) and PUBMED searched on 25 July 2006, limit: 90 days (entry date). We searched the reference lists of relevant articles and contacted investigators of included studies and manufacturers of multifocal intraocular lenses for information about additional published and unpublished studies. SELECTION CRITERIA: All randomised controlled trials comparing a multifocal IOL of any type with a monofocal IOL as control were included. Both unilateral and bilateral implantation trials were included. DATA COLLECTION AND ANALYSIS: Data were collected and trial quality was assessed. Where possible, statistical summary measures were calculated otherwise data were tabulated. MAIN RESULTS: Ten trials were identified, and a further three are pending review. There was significant variability between the trials in which outcomes were reported. Unaided distance acuity was similar in multifocal and monofocal IOLs (standardised mean difference (SMD) 0.03, 95% Confidence Interval (CI) -0.13 to 0.19). There was no statistical difference between multifocal IOLs and monofocals with respect to the proportion of participants achieving 6/6 best corrected visual acuity (Peto odds ratio (OR) 1.05, 95% CI 0.67 to 1.63). Unaided near vision was improved with the multifocal IOLs. Total freedom from use of glasses was achieved more frequently with multifocal than monofocal IOLs (OR for spectacle dependence 0.17, 95% CI 0.12 to 0.24). Adverse effects included reduced contrast sensitivity and the subjective experience of haloes around lights. AUTHORS' CONCLUSIONS: Multifocal IOLs are effective at improving near vision relative to monofocal IOLs. Whether that improvement outweighs the adverse effects of multifocal IOLs will vary between patients. Motivation to achieve spectacle independence is likely to be the deciding factor.

Cataract Extraction↗

PubMed1986

Prenatal growth of the median face.

The growth and development of the median facial region remain incompletely understood. Data concerning the prenatal size and growth rates of facial components are especially lacking. A group of fetuses and newborn infants with apparently normal craniofacial development and body size was therefore studied at autopsy. The interorbital distance and dimensions of the external nose, philtrum (upper lip), and mouth were determined; the growth of morphogenetically related structures--the ethmoid bone and tongue--was also studied. The slopes of linear regressions of these variables against body length indicated that growth of the median facial region proceeds slowly in the latter half of gestation. The center of the face seems to grow slower than the sides of the face. A multivariate technique, factor analysis, identified and ordered relationships among the variables. The best statistical summary of size in the median face was given by four transversely oriented variables, nose breadth, outer orbital distance, inner canthal distance, and mouth width. Within the region, a secondary cluster was dominated by sagittally oriented variables. The second best summary of median facial relationships was provided by three variables of lingual size and was followed by a group of variables representing ethmoidal size. This pattern of growth may represent the effects of a developmental hierarchy. Growth seems to be coordinated along the major axes of the body, with transverse growth controlled more rigidly than sagittal growth. The statistical independence of the three regions suggests that the controls of growth are also separate.

Biometry↗

PubMed1999

Measuring for improvement: from Toyota to thoracic surgery.

BACKGROUND: Measuring quality has become a high priority in the era of managed care. Nevertheless, it can be counterproductive to use the same methods for measuring improvement in surgical procedures and processes as we use for measurement in basic research. Techniques of statistical process control have been used for many years to measure process improvement in industry and are now being applied to health care. METHODS: Examples of using statistical process control charts to monitor coronary artery bypass grafting mortality, intensive care unit admission time, and length of stay are reviewed. RESULTS: The major advantage of using control chart methodology is that it allows one to determine whether the process being evaluated is in fact stable and to detect when significant or special cause variation occurs. CONCLUSIONS: Summary statistics currently provided to purchasers of care and regulatory agencies do not ensure that the processes being evaluated are stable. We need to look at data over time with statistically validated methods such as control charts to better monitor our processes of care and thereby provide accurate statistics.

Coronary Artery Bypass↗

PubMed2006

Growth from birth to age 19 for children in Sweden born in 1981: descriptive values.

AIM: To describe Swedish children's growth (i.e. height, weight and body mass index) from birth to age 19 y. METHODS: Every infant born on the 15th of any month in 1981 and living in Sweden as of 31 December 1989 was sampled. Longitudinal data were collected from childhood and school health records, and analysis by piecewise linear regression gave statistical descriptions of height, weight and body mass index for every age group. RESULTS: The data include measurements of 3107 of 3158 sampled children; 1.6% of individuals are missing, so non-response bias is minimal. Thus, statistical descriptions and comparisons with similar data sets can be based on data with unusually high national representativeness. Selected subgroups (i.e. individuals born outside Sweden, suffering from chronic disease causing major growth impairment, or with birthweight <2500 g) deviate in growth pattern, and exclusion of these subgroups increases means and decreases SD for height but only slightly influences summary statistics for weight and body mass index. CONCLUSION: This study represents, without selection bias, the current growth situation among children and adolescents in Sweden, enabling both epidemiological comparisons over time and comparisons with other national surveys.

Adolescent↗

PubMed2004

Population Graphs: the graph theoretic shape of genetic structure.

Patterns of intraspecific genetic variation result from interactions among both historical and contemporary evolutionary processes. Traditionally, population geneticists have used methods such as F-statistics, pairwise isolation by distance models, spatial autocorrelation and coalescent models to analyse this variation and to gain insight about causal evolutionary processes. Here we introduce a novel approach (Population Graphs) that focuses on the analysis of marker-based population genetic data within a graph theoretic framework. This method can be used to estimate traditional population genetic summary statistics, but its primary focus is on characterizing the complex topology resulting from historical and contemporary genetic interactions among populations. We introduce the application of Population Graphs by examining the range-wide population genetic structure of a Sonoran Desert cactus (Lophocereus schottii). With this data set, we evaluate hypotheses regarding historical vicariance, isolation by distance, population-level assignment and the importance of specific populations to species-wide genetic connectivity. We close by discussing the applicability of Population Graphs for addressing a wide range of population genetic and phylogeographical problems.

Cactaceae↗

PubMedDate not supplied

Treatment of recurrent high grade astrocytoma; results of a systematic review of 1,415 patients.

OBJECTIVE: The optimum treatment strategy for recurrent high grade glioma (anaplastic astrocytoma and glioblastoma multiforme) remains undefined. The objective of this report is to present a systematic analysis of the published clinical trial literature on the therapy of this disease. METHODS: A study protocol was prospectively developed outlining the objectives and methods of the analysis such as; literature search strategy, eligibility criteria for published trials to be included, key data elements to be extracted, and a plan for statistical analysis. Variables of interest were, those describing key features of the study such as publication date and geographic location of reporting institution, characteristics of study population including functional status, details of patient treatment, treatment sequencing and data on clinical outcomes of interest, i.e. time to tumor progression and overall survival. Data were analyzed using SAS version 6.11. Summary statistics were calculated for the primary outcome variables. Data on recognized prognostic variables were recorded in order to adjust the analysis for these parameters. RESULTS: A total of 40 trials (36 non-randomized controlled trials; nRCTs and 4 randomized controlled trials: RCTs) were included in the analysis. Thirty-two of the eligible trials were chemotherapy trials while 7 were radiation therapy trials. One surgical trial met eligibility criteria. A total of 47 treatment arms were analysed which included 1,415 patients. Five chemotherapy groups were studied, i.e. interferons, nitrosoureas, platinums, platinums + nitrosoureas and others. The nitrosoureas were found to significantly extend time to tumor progression compared to all other drugs (26.9 weeks). The nitrosoureas and platinums appear to be the most active agents with regard to overall survival (over 32.0 weeks) as compared with the other drug categories. Patients treated with both a nitrosourea and a platinum compound showed the longest overall survival (40.0 weeks) although this was not significantly different from these drugs used as single agents. Average median survival for patients treated with radiation therapy was 44.7 weeks although selection bias makes these data difficult to compare with those derived from studies of chemotherapy. No definite conclusions can be made regarding surgical therapy in this setting due to limited data. CONCLUSIONS: The nitrosoureas and platinums, either as single agents or as combination chemotherapy, appear to be the most active agents in this disease although few, well designed chemotherapy trials are available for analysis. Due to the limitations of the available data on radiation therapy and surgery, as outlined in this report, additional, well designed clinical trials are needed to define the appropriate role for these modalities in the treatment of recurrent high grade glioma.

Antineoplastic Agents↗

PubMed1985

A statistical test for differences in sexual dimorphism between populations.

Many studies involve comparison of measures of sexual dimorphism between two samples. This comparison is used to test a variety of hypotheses, such as changing environmental conditions. Methods for testing the significance of the difference between two populations tend to be complex, and/or require access to complete original data. We offer a simplified approach which is based on a linear regression model using dummy variables. Our method is computationally simple and can be used with summary statistics (sample size, means, standard deviations) instead of raw data. We present three examples of the application of our method to problems in physical anthropology. We also note that our method has a broader range of applications apart from that of sexual dimorphism.

Anthropometry↗

PubMed2004

Statistical validation of surrogate endpoints: is bone density a valid surrogate for fracture?

In the treatment of osteoporosis using anti-resorptive agents there has been increasing interest in quantifying the relationship between fracture endpoints and surrogates such as bone mineral density (BMD) or bone turnover markers. Statistical methodology constitutes a critical component of assessing surrogate validity. Depending on study designs, data resources, and statistical methods used for analyses, one has to use caution when interpreting results from different analyses, especially when results are disparate. For example, analyses based on individual patient data reported that only a limited proportion of the anti-fracture efficacy was explained by BMD increases for agents such as alendronate, risedronate and raloxifene. Analyses employing meta-regression based on summary statistics, however, indicated that most of the anti-fracture benefits were due to improvements in BMD. In this paper, we review definitions of surrogate endpoints and requirements for their statistical validation. We evaluate whether BMD meets these requirements as a possible surrogate for fracture. Our review indicates that the actual BMD value is correlated with fracture risk and thus BMD is useful in identifying patients that might need treatment. There is limited evidence to support BMD increase with anti-resorptive agents as a reliable substitute for fracture risk reduction. Strengths and limitations for various statistical methods are discussed.

Biomarkers↗