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PubMed1995

Statistical inference in stationary populations.

A fixed ensemble of alternating renewal processes is proposed as a model for stationary populations. This model is applied to explore the relationship between survival times and forward recurrence times. In addition, it is shown that ergodic theory can be applied to the model. An example is presented.

Biometry↗
PubMed1981

Maternal and abortion related deaths in Bangladesh, 1978-1979.

The incidence and causes of pregnancy-related deaths are unknown for most of Asia; only local area studies have been done for Bangladesh. Between December 1978 and May 1979, we interviewed 118 health workers in 63 hospitals and 732 non-hospital facilities to identify case reports of maternal and abortion-related deaths in Bangladesh. Of 1933 pregnancy-related deaths identified, 498 (25.8%) were due to induced abortion. Abortion mortality rates varied significantly in the 18 administrative districts; the highest were in Dinajpur and Chittagong, the most northern and southern districts, and the lowest in Comilla and Noakhali. We used an earlier study of maternal mortality to estimate that about 21,600 pregnancy-related deaths occur each year in Bangladesh. We estimate that about 7.5% of all pregnancy-related deaths were identified in this survey. We infer from these data that safe and effective fertility control, including abortion performed by adequately trained health workers in both in- and out-patient facilities, might be the most appropriate first step in preventing pregnancy-related deaths in Bangladesh.

Abortion, Induced↗
PubMed1989

Biological growth and spread modeled by systems of recursions. I. Mathematical theory.

We study the asymptotic behavior of solutions to a system of recursions u in+1 = Qi[mu n], i = 1, ..., k. The vector operator Q has the origin theta and a positive vector beta as fixed points and is defined for vector-valued functions bounded between theta and gamma where gamma greater than or equal to beta. In addition, Q is order-preserving, commutes with translation, and is continuous in the topology of uniform convergence on compact subsets. Let theta less than or equal to pi much less than beta, and suppose that for all pi much less than alpha much less than beta, Q(n) alpha]----beta as n----infinity. If u0 much greater than pi on a sufficiently large ball and has bounded support, then un propagates with a speed c*(xi) in the direction of the unit vector xi as n----infinity. In certain cases, c*(xi) can be calculated explicitly. The results generalize those of a scalar equation studied by Weinberger.

Genetics, Population↗
PubMed1995

Different trends in serum cholesterol levels among rural and urban populations aged 40-59 in Japan from 1960 to 1990.

In Japan, coronary heart disease mortality is low and has been declining since 1970, despite recent increases in serum cholesterol levels which have been reported in nationwide surveys. Longitudinal and cross-sectional surveys of serum cholesterol levels in rural and urban populations from 1960 to 1990 were reviewed. In the surveys in the 1960s, serum cholesterol levels in urban populations were higher than those in rural populations. An increase in serum cholesterol levels for men and women was observed in all longitudinal studies among rural populations; mean increases in serum cholesterol levels per year were 0.034 mmol/l (p < 0.001) and 0.033 mmol/l (p < 0.001), respectively. These trends were still observed after combining the data from the longitudinal and cross-sectional studies in both men and women (0.027 and 0.028 mmol/l per year, respectively), while there was no significant increase among urban populations. The results of National Nutrition Surveys are consistent with these findings and show that meat consumption per day per capita increased from 23.9 to 66.2 g in rural populations and 51.2 to 77.6 g in urban populations in the 1966 and 1990 surveys. It is suggested that different trends in coronary heart disease mortality should also be apparent in rural and urban populations over this period.

Adult↗
PubMed1998

Standardized structure and modular design of a pharmacokinetic database.

BACKGROUND: The accumulated knowledge on drugs can be used for an individual drug dosage adjustment if it is placed at our disposal in an informatically structured form. THEORY AND METHODS: We have started building up a pharmacokinetic database aimed at adjusting drug dosages, in exemplary form, to patients with renal impairment. Parameters needed for the three dosage adjustment rules (Dettli, Kunin, Holford) and the most general concept of pharmacokinetics constituted the theoretical basis. TWO PROCESSES PERTAIN TO ALL DRUGS: Distribution and elimination. Total drug clearance and at least two parameters representing distribution and elimination processes are closely interdependent in mathematical terms (clearance = volume of distribution*rate of elimination). This relation yields the unifying concept that serves as a prerequisite for a structured recording of 30 assigned pharmacokinetic and pharmacodynamic parameters within an informatic database. SOLUTIONS AND RESULTS: The information is retrieved and referenced from 2383 original publications by means of a standardized input module. The complete database at present contains 15,397 records for 1573 drugs. A programmed meta-analytic algorithm is used to calculate the statistical measures for the central value and variance--as available--from the pooled values of primary records. The statistically standardized parameters are extracted for 6601 pharmacokinetic parameters, and placed at the users disposal with the output module. PRACTICAL UTILITY: Following meta-analysis, published pharmacokinetics can be used as statistical estimates of population parameters. The statistical estimates with variances permit an individual drug dosage adjustment by applying the Bayesian approach or neural networks.

Algorithms↗
PubMed1997

A literature review of low back disorder surveillance measures and risk factors.

OBJECTIVE: The goal of this literature review was to gain insight into low back disorder risk factors via a critical examination of the surveillance measures and analysis techniques employed in existing literature. DESIGN: Fifty-seven original articles were evaluated and categorized as a function of their surveillance measures. BACKGROUND: There have been a plethora of articles concerning the causes of low back disorder, yet no specific risk factors are consistently associated with the development of these disorders. It was hypothesized that different low back surveillance measures and variations in risk factor (dependent variable) measurements have led to the inconsistencies in the literature. METHODS: Five low back disorder surveillance measures and five risk factor categories were defined for this review. Each article was classified on several criteria including: surveillance measures, risk factors, statistical methods, population and type of study. Summary statistics were calculated for the percentage of positive findings as a function of surveillance measure and risk factor category. RESULTS: The most consistently defined surveillance measure was incidence of low back disorder, with 82% of those investigating it as claims from medical records or Occupational Safety and Health Administration records. The combination of surveillance measures and risk factor influenced the outcome of investigations. Ninety-one percent of the direct or video methods of measuring exposure risk factor influenced outcome. Psychosocial measures had positive findings in 70% of the studies examining lost time. Finally, statistical methodology was critical in the outcome of these investigations. CONCLUSIONS: The surveillance measure of incidence had more positive findings, with exposure risk factors and the surveillance measures indicating more advanced stages of low back disorder such as lost time had more positive findings with psychosocial risk factors. Thus, as low back disorders progress to disability, the psychosocial risk factors play a more prominent role. RELEVANCE: In order to prevent low back disorders we must first understand the plethora of epidemiological literature. This literature review provides new insight on the critical issues that have contributed to the results of previous research.

Journal Article↗
PubMed2000

Plasma retinol and tocopherol levels in greek elderly population from an urban and a rural area: associations with the dietary habits.

Data on plasma concentrations of retinol and alpha-tocopherol in elderly (over 65 years) living in the Mediterranean countries are sparse. In the current study, plasma retinol and alpha-tocopherol concentrations were determined in 200 healthy subjects (82 men and 112 women) residing in an urban and in a rural area in South Western Greece. High prevalence of low plasma retinol concentration was observed for both sexes in each area. The 16.7% of males in urban and 25.4% in rural area had plasma retinol levels below 0.3 mg/l. The corresponding values for female subjects were 26% and 20.3%. Plasma alpha-tocopherol was found to be within normal range in the rural area (only one male had plasma alpha-tocopherol below 5 mg/l) while in the urban area 68.3% of men and 62% of women had plasma alpha-tocopherol values below 5 mg/l. Differences in dietary habits between subjects living in the rural and in the urban area were revealed through a weekly food frequency questionnaire. This could partly explain the difference in alpha-tocopherol concentrations between the two areas. The results of this study revealed high risk of vitamin A and E deficiency and suggests that the health care system in Greece should pay more attention on the social and health status of its elderly population.

Aged↗
PubMed1999

On the methods for predicting the effective size of populations under selection.

Inconsistencies between equations for the effective population size under selection obtained by two different approaches are explained. In one approach, the effective population size is predicted from the drift in the frequency of a neutral allele, accounting for the accumulation of selective advantage over generations. The second approach is based on the rate of inbreeding, using the concept of long-term genetic contributions. It is shown that the long-term genetic contribution approach leads to an identical result to the drift approach, if the effect of mates on the long-term genetic contributions is correctly accounted for.

Gene Frequency↗
PubMed2002

Atopy, asthma, and antibodies to Ascaris among rural and urban children in Kenya.

OBJECTIVE: The purpose of this study was to evaluate differences in the relationship between asthma and immune responses to allergens in children living in rural and urban areas of Kenya. STUDY DESIGN: Children (mean age, 11 years) from Kabati (n = 136), a rural village, and Thika (n = 129), a small town, were studied by skin testing and serum immunoglobulin E (IgE) and immunoglobulin G (IgG) antibody measurement. Asthma was evaluated by symptoms, as well as spirometry before and after vigorous exercise to test for exercised-induced bronchospasm (EIB). School children from a study performed in Atlanta, Georgia, were used for comparison of anthropometric and immunologic results. RESULTS: Compared with the urban area of Kenya, children living in the rural area had a lower percentage of body fat, smaller and fewer skin test responses to allergens, a higher prevalence of IgE antibodies to Ascaris (67% vs 26%) and 10-fold higher total IgE. In the urban area of Kenya, there was a strong correlation between EIB and atopy determined both by IgE antibodies (P =.02) and skin tests (P =.002). By contrast, in the rural area, none of the 13 children with EIB were skin-test positive (vs 13/109 of children without EIB). CONCLUSIONS: Among the rural children, there was no association between immune responses to allergens and airway-related symptoms or reactivity. The association between asthma and atopy seen in the town of Thika may represent an important step in the increase in asthma seen both in urban Africa and in the West.

Adolescent↗
PubMed1995

Report from a Nordic workshop on CD34+ cell analysis: technical recommendations for progenitor cell enumeration in leukapheresis from multiple myeloma patients. Nordic Myeloma Study Group Laboratories.

Recently, high-dose chemo- and radiotherapy for newly diagnosed young patients with multiple myeloma has been established in member centers of the Nordic Myeloma Study Group (NMSG). The treatment includes supportive use of autologous hematopoietic blood progenitors harvested by leukapheresis. Safe and adequate hematopoietic support with minimal toxicity requires optimization of the number and quality of harvested progenitors. We have therefore established a workshop consisting of the 11 laboratories within the NMSG with the aim of developing recommendations for enumeration of CD34-positive cells. In this first workshop report, we discuss technical variables affecting the enumeration of progenitors harvested by leukapheresis and make specific recommendations. The products are analyzed within 4 h following erythrocyte lysis using the Ortho lysing solution for 8-10 minutes. A sample containing 0.5-1.0 x 10(6) nucleated cells is incubated with the test or control antibody (anti-CD34 = HPCA-2PE and Ms IgG1PE from Becton Dickinson) at dilutions of 1:10 to 1:40 in a final volume of 1 ml. The samples are incubated 15 minutes at ambient temperature, washed two to three times, and fixed with 1% paraformaldehyde (150 microliters/pellet) for a minimum of 10 minutes. Flow cytometric analysis is performed on 50,000 cellular events with debris eliminated. The estimation of CD34-positive cells can be performed on an FL2-side-scatter plot after marking of a positive population containing > 50 events. Using quadrant statistics, this population can be identified in the upper left quadrant, among cells with the side-scatter profile of small lymphocytic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1990

Zinc in breast milk during prolonged lactation: comparison between the UK and the Gambia.

A total of 580 breast milk samples were collected from 56 lactating women living in a rural village community in The Gambia, West Africa, and 92 samples were obtained from 57 lactating women living in Cambridge, England. Total zinc content of each sample was measured by atomic absorption spectrometry, and pooled samples of the Gambian breast milks, representing successive periods of lactation, were fractionated into fat, whey and insoluble casein fractions, to examine zinc distribution. The two sets of milks both exhibited a dramatic decline in total zinc concentrations with increasing duration of lactation, in common with previous studies. However, the UK milks unexpectedly had lower zinc contents at all stages than the Gambian milks. Milk zinc levels were not significantly related to either maternal age or parity in the Gambian women. The proportion of zinc found in the sedimentable fraction remained nearly constant with increasing duration of lactation, but the proportion found in the fat fraction increased and the proportion in the whey fraction declined. These observations are potentially relevant for estimations of milk zinc availability and the fulfillment of zinc requirements by infants, and hence for infant feeding practices.

Adolescent↗