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PubMed2006

Pattern of cause-specific childhood mortality in a malaria endemic area of Burkina Faso.

BACKGROUND: Reliable mortality data are a prerequisite for planning health interventions, yet such data are often not available in developing countries, particularly in sub-Saharan Africa (SSA). Demographic surveillance systems (DSS) implementing the verbal autopsy (VA) method are the only possibility to observe cause-specific mortality of a population on a longitudinal basis in many countries. METHODS: This paper reports all-cause and cause-specific mortality rates in children under the age of five years from 1999 until 2003 in a malaria holoendemic area of north-western Burkina Faso. The DSS of the Nouna Health Research Centre, in which VA data were analysed, covers a rural population of about 30,000 (41 villages) and an urban population of about 25,000 (Nouna town). RESULTS: A total of 1,544 deaths were analysed, 87 (6%), 225 (14%), 317 (21%) and 915 (59%) of which occurred in the periods < 1 month, 1-5 months, 6-11 months and 1-4 years respectively. All cause mortality rates of children under five years were higher in the rural than the urban area (34 vs 24 per 1,000 person-years) and in the rainy than the dry season (35 vs 29 per 1,000 person-years). Malaria was the most frequent diagnosis (42%) with peak mortality rates in infants aged 6-11 months. CONCLUSION: Malaria is the most important cause of death in this remote area of SSA, even considering the low specificity of malaria diagnosis in young children. Strengthening the existing malaria control tools is of prime importance to reduce the high childhood mortality in the endemic areas of SSA.

Age Distribution↗
PubMed1999

Approximate Monte Carlo conditional inference in exponential families.

This article presents an algorithm for approximate frequentist conditional inference on two or more parameters for any regression model in the Generalized Linear Model (GLIM) family. We thereby extend highly accurate inference beyond the cases of logistic regression and contingency tables implimented in commercially available software. The method makes use of the double saddlepoint approximations of Skovgaard (1987, Journal of Applied Probability 24, 875-887) and Jensen (1992, Biometrika 79, 693-703) to the conditional cumulative distribution function of a sufficient statistic given the remaining sufficient statistics. This approximation is then used in conjunction with noniterative Monte Carlo methods to generate a sample from a distribution that approximates the joint distribution of the sufficient statistics associated with the parameters of interest conditional on the observed values of the sufficient statistics associated with the nuisance parameters. This algorithm is an alternate approach to that presented by Kolassa and Tanner (1994, Journal of the American Statistical Association 89, 697-702), in which a Markov chain is generated whose equilibrium distribution under certain regularity conditions approximates the joint distribution of interest. In Kolassa and Tanner (1994), the Gibbs sampler was used in conjunction with these univariate conditional distribution function approximations. The method of this paper does not require the construction and simulation of a Markov chain, thus avoiding the need to develop regularity conditions under which the algorithm converges and the need for the data analyst to check convergence of the particular chain. Examples involving logistic and truncated Poisson regression are presented.

Algorithms↗
PubMed2005

Real-time kinetics of gene activity in individual bacteria.

Protein levels have been shown to vary substantially between individual cells in clonal populations. In prokaryotes, the contribution to such fluctuations from the inherent randomness of gene expression has largely been attributed to having just a few transcripts of the corresponding mRNAs. By contrast, eukaryotic studies tend to emphasize chromatin remodeling and burst-like transcription. Here, we study single-cell transcription in Escherichia coli by measuring mRNA levels in individual living cells. The results directly demonstrate transcriptional bursting, similar to that indirectly inferred for eukaryotes. We also measure mRNA partitioning at cell division and correlate mRNA and protein levels in single cells. Partitioning is approximately binomial, and mRNA-protein correlations are weaker earlier in the cell cycle, where cell division has recently randomized the relative concentrations. Our methods further extend protein-based approaches by counting the integer-valued number of transcript with single-molecule resolution. This greatly facilitates kinetic interpretations in terms of the integer-valued random processes that produce the fluctuations.

Algorithms↗
PubMed2001

Geographical distribution of cardiac arrest in Nottinghamshire.

BACKGROUND: to analyse the incidence of out-of-hospital cardiac arrest in Nottinghamshire; to ascertain its geographical distribution; and to determine whether the geography of coronary heart disease mortality and out-of-hospital cardiac arrest are the same. METHODS AND RESULTS: population based, retrospective study in the County of Nottinghamshire with a total population of 993,914 in an area of 2183 km2 divided into 191 electoral areas. In the 4 years from 1 January, 1991 to 31 December, 1994, 1634 patients sustained a cardiac arrest attributed to a cardiac cause (International Classification of Diseases codes 390-414 and 420-429) and were attended by the Nottinghamshire Ambulance Service. The overall crude mean incidence rate of community cardiac arrest per electoral area was 40.2 per 100,000 population (range 0-121.2). Thirteen electoral areas, relatively deprived according to the Townsend score, had a significantly greater than expected incidence rate of cardiac arrest (median of 75.6/100,000 per electoral area; interquartile range (IQR) 65.3, 83.8). Twelve relatively affluent electoral areas had a significantly lower than expected incidence rate (median of 18.5/100,000 per area (IQR 13.0, 28.7). After adjusting for deprivation index, there were no differences in coronary heart disease (CHD) mortality and community cardiac arrest in urban and rural electoral areas. Apart from response times by ambulance crews, the events that follow the cardiac arrest such as bystander resuscitation, ventricular fibrillation found as the presenting rhythm and survival were similar in all electoral areas. CONCLUSIONS: increasing level of deprivation is associated with areas of increased incidence of out-of-hospital cardiac arrest in Nottinghamshire, and the effect is apparently different from that on CHD mortality. There is scope for reducing incidence rates of community cardiac arrest and to introduce strategies to improve survival in areas identified as having high rates of community cardiac arrest.

Age Distribution↗
PubMed1993

Trends in breast cancer incidence in Sweden 1958-1988 by time period and birth cohort.

Statistics from the Swedish National Cancer Registry based on all 110,658 cases of invasive breast cancer during the 31-year period 1958-1988 were analysed. Age-specific incidence rates increased over successive calendar periods. The average annual increase in the age-standardised incidence rate was 1.3%, with the greatest percentage changes among the youngest age groups. During the latter half of the study period, the rates of increase tended to diminish in the youngest age groups and even reversed significantly among women from 75 years of age. In analyses using age-period-cohort models, the best fit of the cancer incidence data was found for the full model which simultaneously considered the effects of age, period and cohort. Cohort effects were found to be more important than period effects, in terms of model fit. These effects emerged as a seemingly consistent, and in a logarithmic scale, fairly linear increase in the relative risk of breast cancer incidence with a 3-fold elevation in women born in the 1950's relative to those born in the 1880's. It is concluded that the rising breast cancer incidence in Sweden is explained chiefly by birth cohort effects, which indicate persistent secular changes in largely unknown risk factors associated with life style. We could not in the present data see any clear evidence for an adverse effect of contraceptive or replacement sex steroids on breast cancer incidence.

Adult↗
PubMed2000

Cancer of the upper gastrointestinal tract among patients with pernicious anemia: a case-cohort study.

BACKGROUND: An association between pernicious anemia and stomach cancer has been established in several studies. An increased risk of pancreatic and esophageal cancers has also been reported among pernicious anemia patients. The aim of this case-cohort study was to identify additional risk factors for cancer of the esophagus, stomach, and pancreas among patients with pernicious anemia. METHODS: A population-based cohort of 4586 patients with pernicious anemia was linked to the Swedish Cancer Registry to identify patients who subsequently developed cancers of the esophagus, stomach, or pancreas using a case-cohort design. A subcohort consisting of 4% of the cohort was randomly selected to serve as the comparison group. Information on medical history, smoking habits, and alcohol use was retrieved from medical charts and analyzed for cancer patients and subcohort members. RESULTS: We could not identify any risk factors other than pernicious anemia for stomach cancer. For pancreatic and esophageal cancer, younger age at diagnosis of pernicious anemia was associated with an increased risk. A prior gastric resection, smoking and alcohol abuse were more frequent among esophageal cancer cases than in the subcohort. CONCLUSIONS: We conclude that a causal relationship between pernicious anemia and subsequent development of esophageal or pancreatic cancers still remains unproven. For esophageal cancer, confounding by smoking and alcohol use is the likely explanation of earlier reports of an association. In the case of stomach cancer, both the inflammatory process, secondary to the pernicious anemia, and pernicious anemia per se may be factors leading to malignant transformation.

Adult↗
PubMed1999

Epidemiologic, bacteriologic, and long-term follow-up data of children with acute hematogenous osteomyelitis and septic arthritis: a ten-year review.

A total of 69 children with acute hematogenous osteomyelitis and 48 with septic arthritis admitted in the period 1978 through 1987 were included in a retrospective review. Epidemiologic and bacteriologic data were analyzed and compared with those of an earlier study (1965 through 1975), confined to the same geographic area. Long-term outcome was evaluated by a questionnaire and clinical and radiographic follow-up. A significant increase in the admission rate for both disorders was observed. The long-term outcome was favorable: major sequelae were found in three patients (3%), minor sequelae in two patients (2%). The benign long-term outcome may well be related to rapid hospital admission and appropriate long-lasting antibiotic treatment.

Adolescent↗
PubMed1996

Spatial sampling and filtering of EEG with spline laplacians to estimate cortical potentials.

The electroencephalogram (EEG) is recorded by sensors physically separated from the cortex by resistive skull tissue that smooths the potential field recorded at the scalp. This smoothing acts as a low-pass spatial filter that determines the spatial bandwidth, and thus the required spatial sampling density, of the scalp EEG. Although it is better appreciated in the time domain, the Nyquist frequency for adequate discrete sampling is evident in the spatial domain as well. A mathematical model of the low-pass spatial filtering of scalp potentials is developed, using a four concentric spheres (brain, CSF, skull, and scalp) model of the head and plausible estimates of the conductivity of each tissue layer. The surface Laplacian estimate of radial skull current density or cortical surface potential counteracts the low-pass filtering of scalp potentials by shifting the spatial spectrum of the EEG, producing a band-passed spatial signal that emphasizes local current sources. Simulations with the four spheres model and dense sensor arrays demonstrate that progressively more detail about cortical potential distribution is obtained as sampling is increased beyond 128 channels.

Cerebral Cortex↗
PubMed2003

Radiological effects on populations of Oligochaeta in the Chernobyl contaminated zone.

A detailed investigation of 3 populations of Oligochaete species (Dero obtusa, Nais pseudobtusa and Nais pardalis) has been carried out in a contaminated lake of the close-in Chernobyl zone and in a control lake. Hydrochemical indices and concentrations of heavy metals, chloro-organic compounds and (90)Sr in bottom sediments have been measured. Absorbed doses were calculated on the basis of the results of radiochemical analysis and assessed directly with thermoluminescent dosimeters (TLD). Stimulation of paratomous division (asexual reproduction) was found in one species of worm (D. obtusa), and activation of sexual reproduction in the two other species studied. An increase in the amount of cytogenetic damage in the somatic cells of worms from the contaminated lake was found and an attempt was made to assess the relative contributions of radiation and chemical exposure on the basis of analyses of inter-cellular aberration distributions and the types of chromosome aberrations observed in the cells.

Animals↗
PubMedDate not supplied

Chance or design? Some specific considerations concerning synaptic boutons in cat visual cortex.

To understand the rules by which axons lay down their synaptic boutons we analyzed the linear bouton distributions in 39 neurons (23 spiny, 13 smooth) and 3 thalamic axons, which were filled intracellularly with horseradish peroxidase (HRP) during in vivo experiments in cat area 17. The variation of the total number of boutons and the total axonal length was large (789-7,912 boutons, 12-126 mm). The overall linear bouton density for smooth cells was higher than that of spiny cells and thalamic afferents (mean +/- sd, 110 +/- 21 and 78 +/- 27 boutons per mm of axonal length). The distribution of boutons varied according to their location on the tree. Distal axon collaterals (first and second order segments in Horton-Strahler ordering) of smooth neurons had a 3.5 times higher, spiny cells and thalamic afferents a 2 times higher bouton density compared to the higher order (more proximal) segments. The distribution of interbouton intervals was positively skewed and similar for cells of the same type. In most cases a gamma-distribution fitted well, but the distributions had a tendency to have a heavier tail. To a first approximation these bouton distributions are consistent with both diffuse and specific models of interneuronal connections. Quite simple rules can explain these distributions and the connections between the different classes of neurons.

Animals↗
PubMed2001

Simultaneous modelling of operative mortality and long-term survival after coronary artery bypass surgery.

Typical analyses of lifetime data treat the time to death or failure as the response variable and use a variety of modelling strategies such as proportional hazards or fully parametric, to investigate the relationship between the response and covariates. In certain circumstances it may be more natural to view the distribution of the response variable as consisting of two or more parts since the survival curve appears segmented. This article addresses such a scenario and we propose a model for simultaneously investigating the effects of covariates over the two segments. The model is an analogue of that proposed by Lambert for zero-inflated Poisson regression. The application is central to the model development and is concerned with survival after coronary artery bypass surgery. Here operative mortality, defined as death within 30 days after surgery, and long-term mortality, are viewed as distinct outcomes. For the application considered, the survivor function displays much steeper descent during the first 30 days after surgery, that is, for operative mortality, than after this period. An investigation of the effects of covariates on operative and long-term mortality after coronary artery bypass surgery illustrates the usefulness of the proposed model.

Age Factors↗
PubMedDate not supplied

Two dental implants designed for immediate loading: a finite element analysis.

PURPOSE: The aim of this study was to evaluate by finite element analysis the influence of the design of 3 different dental implants on micromovements, cervical shearing stress intensity, and stress distribution after occlusal loading. MATERIALS AND METHODS: The first investigated implant was a classical cylinder, the second was reinforced by 2 bicortical locking pins, and the third was an expanding dental implant. The parameters analyzed were the implant's geometry, the quality of the cancellous bone, and the orientation of occlusal loading. RESULTS: It was found that initial stability of the locking pin implant was greater than the initial stability of the other investigated implant designs, regardless of the quality of cancellous bone and orientation of occlusal loading; in low-rigidity cancellous bone, under a horizontal load (500 N), decreasing displacement compared to those of the other investigated implants was 16 microm. The apical expansion and locking pin implants exhibited favorable behavior regarding the distribution and intensity of cervical shearing stresses; in low-rigidity cancellous bone, under horizontal load, decreasing cervical stresses compared with those of the cylindric implant were 10 MPa for the apical expansion implant and 150 MPa for the locking pin implant. DISCUSSION: For the cylindric implant, stresses were concentrated in the neck region; for the apical expansion implant, stresses were evenly distributed from the neck to the apex of the implant. For the locking pin implant, stresses around the neck were moderate and appeared concentrated around the pins. CONCLUSIONS: Initial stability of the pin implant was greater than that of the expanding implant, but the expanding implant showed the most favorable stress distribution.

Bite Force↗
PubMedDate not supplied

The estimated magnitude of AIDS in Brazil: a delay correction applied to cases with lost dates.

The number of HIV-infected people is an important measure of the magnitude of the AIDS epidemic in Brazil and allows for comparison with epidemic patterns in other countries. This quantity can be estimated from the number of reported AIDS cases, which in turn needs to be corrected for the distribution of reporting delays and under-recording of cases. These distributions are unknown and must also be estimated from the recorded dates, which were missed to the Brazilian National AIDS registry. This paper estimates the number of AIDS cases diagnosed by inputting the lost information based on an estimate of the pattern in registration delay until 1996. We first fitted a non-stationary bivariate Poisson regression model to estimate the pattern in reporting delay. In the subsequent steps these models were applied to input new data, thus replacing the missing information, and to estimate the magnitude of the AIDS epidemic in the country. Model estimates ranged from 36,000 to 50,000 AIDS cases diagnosed in Brazil and still unreported. Therefore, the epidemic was 20 to 30% greater than known from the available information as of February 1999. To be useful to health policy-makers, the surveillance system based on officially reported AIDS cases must be continuously improved.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Redundancy reduction and sustained firing with stochastic depressing synapses.

Many synapses in the CNS transmit only a fraction of the action potentials that reach them. Although unreliable, such synapses do not transmit completely randomly, because the probability of transmission depends on the recent history of synaptic activity. We examine how a variety of spike trains, including examples recorded from area V1 of monkeys freely viewing natural scenes, are transmitted through a realistic model synapse with activity-dependent depression arising from vesicle depletion or postrelease refractoriness. The resulting sequences of transmitted spikes are significantly less correlated, and hence less redundant, than the presynaptic spike trains that generate them. The spike trains we analyze, which are typical of those recorded in a variety of brain regions, have positive autocorrelations because of the occurrence of variable length periods of sustained firing at approximately constant rates. Sustained firing may, at first, seem inconsistent with input from depressing synapses. We show, however, that such a pattern of activity can arise if the postsynaptic neuron is driven by a fixed population of direct, "feedforward" inputs accompanied by a variable number of delayed, "reverberatory" inputs. This leads to a prediction for the number and latency distribution of the inputs that typically drive a cortical neuron.

Action Potentials↗
PubMedDate not supplied

Equity in health care utilization: further tests based on hurdle models and Swedish micro data.

This paper tests the null hypothesis of no horizontal inequity in delivery of health care by use of count data hurdle models and Swedish micro data. It differs from most earlier work in three principal ways: First, the tests are carried out separately for physician and hospital care; second, the tests are carried out separately for the probability of seeking care and the amount of care received (given any use); and third, the tests are based on a model that includes several socioeconomic variables, e.g. income, education and size of community of residence. The paper rejects the hypothesis of no inequity because socioeconomic factors also have significant effects on utilization, e.g. income and size of community of residence. Size of community of residence has a positive significant effect on the frequency of physician visits but not on the probability of visiting a physician.

Adolescent↗
PubMed2002

Annual rates of admission and seasonal variations in hospitalizations for heart failure.

AIMS: To investigate the annual hospitalization rate and seasonal variation in confirmed heart failure (HF) admissions. METHODS AND RESULTS: Records from all admissions to one hospital during 1 year with a HF diagnostic code were reviewed. From 1953 admissions, 595 were excluded because they did not fulfill the diagnostic criteria. A total of 1069 patients had 1358 admissions with confirmed HF. Mean age was 74.8 +/- 11.5 years, 42% were males. The admission data were matched with data from the municipal census with 537,666 people aged > or = 15 years. There were 2.5 admissions per 1000 for the adult population and 26.5/1000 in those aged > or = 80 years. There were 444 males and 625 females, giving a higher rate of admission for female patients 2.2/1000 vs. 1.7/1000 (P < 0.0001), although age adjusted rates in females were higher only for > or = 80 years. Echocardiogram was performed in 706 patients (66%), 325 (46%) had a normal ejection fraction. This proportion increased in females--64% vs. 29% males--and in older patients--55% in > or = 75 vs. 39% in < 75 years. Mortality during the first admission of 1996 was 8.3%. There was a seasonal variation in HF hospitalizations (P < 0.0001) peaking at 25% above average in January and dipping to 33% below average in August. CONCLUSION: The rate of HF admissions was 2.5/1000 with an elderly preponderance and a higher rate of admission in males < 80 years and in females > or = 80 years. A seasonal variation ranging from 25% above average in January to 33% below average in August was observed.

Adolescent↗
PubMed2002

Heat wave morbidity and mortality, Milwaukee, Wis, 1999 vs 1995: an improved response?

OBJECTIVES: This study examined whether differences in heat alone, as opposed to public health interventions or other factors, accounted for the reduction in heat-related deaths and paramedic emergency medical service (EMS) runs between 1995 and 1999 during 2 heat waves occurring in Milwaukee, Wis. METHODS: Two previously described prediction models were adapted to compare expected and observed heat-related morbidity and mortality in 1999 based on the city's 1995 experience. RESULTS: Both models showed that heat-related deaths and EMS runs in 1999 were at least 49% lower than levels predicted by the 1995 relation between heat and heat-related deaths or EMS runs. CONCLUSIONS: Reductions in heat-related morbidity and mortality in 1999 were not attributable to differences in heat levels alone. Changes in public health preparedness and response may also have contributed to these reductions.

Age Distribution↗
PubMed1994

Aneuploidy in somatic cells of in utero exposed A-bomb survivors in Hiroshima.

Cytogenetic data on cultured lymphocytes of the in utero exposed A-bomb survivors in the RERF Adult Health Study cohort have been analyzed using the G-banding technique to determine the frequency of aneuploid cells. The data consist of blood samples collected between 1985 and 1987 from 264 Hiroshima individuals for whom DS86 maternal uterine dose estimates are available: 124 proximally exposed (74 males and 50 females) with an estimated dose of 0.005 Sv or more, and 140 distally exposed (76 males and 64 females) with a dose estimate of 0 Sv, assuming the neutron relative biological effectiveness (RBE) of 10. A main feature of aneuploidy was that aneuploid frequency in autosomes depended generally on chromosome length; aneuploidies were significantly more frequent in shorter chromosomes than in longer chromosomes. The frequency of aneuploidies also depended on type, with chromosome loss approximately five times more frequent than chromosome gain. However, chromosome 21, as well as the sex chromosomes, were notable in that aneuploidy was much more frequent for these chromosomes than would be predicted from a simple relationship with length. X chromosome aneuploidies were significantly more frequent in females than in males. There was no dependence of aneuploid frequencies on dose when measured 40 years after the exposure.

Adult↗