984 resultados para Accumulation rate, n-alkanes C29-C33 per year
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Lung cancer mortality in men from the European Union (EU) peaked in the late 1980s at an age-standardised (world standard population) rate over 53/100,000 and declined subsequently to reach 44/100,000 in the early 2000s. To provide a comprehensive picture of recent trends in male lung cancer mortality in Europe, we analyzed available data from the World Health Organization up to 2009 and predicted future rates to 2015. Lung cancer mortality rates in EU men continued to fall over recent years, to reach a value of 41.1/100,000 in 2005-2009. The fall was similar at all-ages and in middle-aged men (less than 2% per year over most recent years), but was appreciably larger in young men (aged 20-44years, over 5% per year). A favourable trend is thus likely to be maintained in the foreseeable future, although the predicted overall EU rate in 2015 is still over 35/100,000, i.e., higher than the US rate in 2007 (33.7/100,000). Over most recent calendar years, overall male lung cancer rates were around 35-40/100,000 in western Europe, as compared to over 50/100,000 in central and eastern Europe. Within western Europe, lung cancer rates were lower in northern countries such as Sweden, but also Finland and the UK (below 30/100,000), where the tobacco-related epidemic started earlier and rates have long been declining, whereas mortality was high in Belgium (51.6), France (42.3), the Netherlands and Spain (around 43.0), where the epidemic started later but is persisting. Widespread measures for smoking control and cessation in middle-aged European men, i.e., in the generations where smoking prevalence used to be high, would lead to appreciable reductions in male lung cancer mortality in the near future. This is particularly urgent in central and eastern European countries.
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This adult cohort determined the incidence and patients' short-term outcomes of severe traumatic brain injury (sTBI) in Switzerland and age-related differences. A prospective cohort study with a follow-up at 14 days was performed. Patients ≥16 years of age sustaining sTBI and admitted to 1 of 11 trauma centers were included. sTBI was defined by an Abbreviated Injury Scale of the head (HAIS) score >3. The centers participated from 6 months to 3 years. The results are presented as percentages, medians, and interquartile ranges (IQRs). Subgroup analyses were performed for patients ≤65 years (younger) and >65 (elderly). sTBI was observed in 921 patients (median age, 55 years; IQR, 33-71); 683 (74.2%) were male. Females were older (median age, 67 years; IQR, 42-80) than males (52; IQR, 31-67; p<0.00001). The estimated incidence was 10.58 per 100,000 inhabitants per year. Blunt trauma was observed in 879 patients (95.4%) and multiple trauma in 283 (30.7%). Median Glasgow Coma Score (GCS) on the scene was 9 (IQR 4-14; 8 in younger, 12 in elderly) and in emergency departments 5 (IQR, 3-14; 3 in younger, 8 in elderly). Trauma mechanisms included the following: 484 patients with falls (52.6%; younger, 242 patients [50.0%]; elderly, 242 [50.0%]), 291 with road traffic accidents (31.6%; younger, 237 patients [81.4%]; elderly, 54 [18.6%]), and 146 with others (15.8%). Mortality was 30.2% (24.5% in younger, 40.9% in elderly). Median GCS at 14 days was 15 (IQR, 14-15) without differences among subgroups. Estimated incidence of sTBI in Switzerland was low, age was high, and mortality considerable. The elderly had higher initial GCS and a higher death rate, but high GCS at 14 days.
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Background: Several studies have shown that treatment with HMG-CoA reductase inhibitors (statins) can reduce coronary heart disease (CHD) rates. However, the cost effectiveness of statin treatment in the primary prevention of CHD has not been fully established. Objective: To estimate the costs of CHD prevention using statins in Switzerland according to different guidelines, over a 10-year period. Methods: The overall 10-year costs, costs of one CHD death averted, and of 1 year without CHD were computed for the European Society of Cardiology (ESC), the International Atherosclerosis Society (IAS), and the US Adult Treatment Panel III (ATP-III) guidelines. Sensitivity analysis was performed by varying number of CHD events prevented and costs of treatment. Results: Using an inflation rate of medical costs of 3%, a single yearly consultation, a single total cholesterol measurement per year, and a generic statin, the overall 10-year costs of the ESC, IAS, and ATP-III strategies were 2.2, 3.4, and 4.1 billion Swiss francs (SwF [SwF1 = $US0.97]). In this scenario, the average cost for 1 year of life gained was SwF352, SwF421, and SwF485 thousand, respectively, and it was always higher in women than in men. In men, the average cost for 1 year of life without CHD was SwF30.7, SwF42.5, and SwF51.9 thousand for the ESC, IAS, and ATP-III strategies, respectively, and decreased with age. Statin drug costs represented between 45% and 68% of the overall preventive cost. Changing the cost of statins, inflation rates, or number of fatal and non-fatal cases of CHD averted showed ESC guidelines to be the most cost effective. Conclusion: The cost of CHD prevention using statins depends on the guidelines used. The ESC guidelines appear to yield the lowest costs per year of life gained free of CHD.
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Co-trimoxazole reduces mortality in HIV-infected adults with tuberculosis (TB), and in vitro data suggest potential antimycobacterial activity of co-trimoxazole. We aimed to evaluate whether prophylaxis with co-trimoxazole is associated with a decreased risk of incident TB in Swiss HIV Cohort Study (SHCS) participants. We determined the incidence of TB per 1,000 person-years from January 1992 to December 2012. Rates were analyzed separately in participants with current or no previous antiretroviral treatment (ART) using Poisson regression adjusted for CD4 cell count, sex, region of origin, injection drug use, and age. A total of 13,431 cohort participants contributed 107,549 person-years of follow-up: 182 patients had incident TB-132 (73%) before and 50 (27%) after ART initiation. The multivariable incidence rate ratios for cumulative co-trimoxazole exposure per year for persons with no previous ART and current ART were 0.70 (95% confidence interval [CI], 0.55 to 0.89) and 0.87 (95% CI, 0.74 to 1.0), respectively. Co-trimoxazole may prevent the development of TB among HIV-positive persons, especially among those with no previous ART.
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Since the mid 90's, international actors as well as governmental actors have raised their interest into the development of irrigation's potential that is still largely unexploited in Niger. It seems all the more interesting as it could answer the needs of a fast growing population (3.3% per year). However, if everyone agrees on the need to development this system, the current implementation triggers questions on the process itself and its side effects. National and international policies on this matter were build upon an historical process through colonial, post-colonial and then the late 1980's neoliberal structures, leading to a business model that reveals a discrepancy between the state logic and the farming one. This business model asks for a high capacity of mobilization of resources unachievable for many, especially when they want to address small-scale irrigation (area
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In the decade of the 1990s, China’s feed sector became increasingly privatized, more feed mills opened, and the scale of operation expanded. Capacity utilization remained low and multi-ministerial supervision was still prevalent, but the feed mill sector showed a positive performance overall, posting a growth rate of 11 percent per year. Profit margin over sales was within allowable rates set by the government of China at 3 to 5 percent. Financial efficiency improved, with a 20 percent quicker turnover of working capital. Average technical efficiency was 0.805, as more efficient feed mills increasingly gained production shares. This study finds evidence that the increasing privatization explains the improved performance of the commercial feed mill sector. The drivers that shaped the feed mill sector in the 1990s have changed with China’s accession to the World Trade Organization. With the new policy regime in place, the study foresees that, assuming an adequate supply of soy meal and an excess capacity in the feed mill sector, it is likely that China will allow corn imports up to the tariff rate quota (TRQ) of 7.2 mmt since the in-quota rate is very low at 1 percent. However, when the TRQ is exceeded, the import duty jumps to a prohibitive out-quota rate of 65 percent. With an import duty for meat of only 10 to 12 percent, China would have a strong incentive to import meat products directly rather than bringing in expensive corn to produce meat domestically. This would be further reinforced if structural transformation in the swine sector would narrow the cost differential between domestic and imported pork.
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Pseudomonas aeruginosa, une bactérie environnementale ubiquitaire, est un des pathogènes nosocomiaux les plus fréquents aux soins intensifs. La source de ce microorganisme peut être soit endogène, 2,6 à 24 % des patients hospitalisés étant colonisés au niveau digestif, soit exogène. La proportion des cas d'infections à P. aeruginosa d'origine exogène, donc secondaires à une transmission par manuportage ou par l'eau du réseau utilisée pour la toilette ou d'autres soins, reste débattue. Or une meilleure évaluation du taux d'infections exogènes est importante pour la mise en place de mesures de contrôle appropriées. Le but de cette étude était de déterminer sur une période de 10 ans les rôles respectifs des sources exogènes (robinets, autres patients) et endogène dans la colonisation et/ou l'infection par P.aeruginosa chez les patients des Soins Intensifs, ainsi que de documenter les variations épidémiologiques au cours du temps. L'étude a été menée dans les unités de Soins Intensifs du Centre Hospitalier Universitaire Vaudois (CHUV). Les patients colonisés et/ou infectés par P. aeruginosa entre 1998 et 2007ont été identifiés via la base de données du laboratoire de microbiologie. Ils ont été inclus dans l'étude s'ils étaient hospitalisés dans une des unités de Soins Intensifs, Durant cette période, des prélèvements pour recherche de P. aeruginosa ont été effectués sur des robinets des soins intensifs. Un typage moléculaire a été effectué sur toutes les souches cliniques et environnementales isolées en 1998, 2000, 2003, 2004 et 2007. Les patients inclus dans l'étude ont été répartis en quatre catégories (A-D) selon le résultat du typage moléculaire leur souche de P. aeruginosa. La catégorie A inclut les cas pour lesquels le génotype de P. aeruginosa est identique à un des génotypes retrouvé dans l'environnement. La catégorie B comprend les cas pour lesquels le génotype est identique à celui d'au moins un autre patient. La catégorie C comprend les cas avec un génotype unique et la catégorie D comprend les cas pour lesquels la souche était non disponible pour le typage. Les cas des catégories A et B sont considérés comme ayant une origine exogène. Au cours des années de l'étude, le nombre d'admissions aux soins intensifs est resté stable. En moyenne, 86 patients par année ont été identifiés colonisés ou infectés par P. aeruginosa aux Soins Intensifs. Durant la première année d'investigation, un grand nombre de patients colonisés par une souche de P. aeruginosa identique à une de celles retrouvées dans l'environnement a été mis en évidence. Par la suite, possiblement suite à l'augmentation de la température du réseau d'eau chaude, le nombre de cas dans la catégorie A a diminué. Dans la catégorie B, le nombre de cas varie de 1,9 à 20 cas/1000 admissions selon les années. Ce nombre est supérieur à 10 cas/1000 admissions en 1998, 2003 et 2007 et correspond à des situations épidémiques transitoires. Tout au long des 10 ans de l'étude, le nombre de cas dans la catégorie C (source endogène) est demeuré stable et indépendant des variations du nombre de cas dans les catégories A et B. En conclusion, la contribution relative des réservoirs endogène et exogène dans la colonisation et/ou l'infection des patients de soins Intensifs varie au cours du temps. Les facteurs principaux qui contribuent à de telles variations sont probablement le degré de contamination de l'environnement, la compliance des soignants aux mesures de contrôle des infections et la génétique du pathogène lui-même. Etant donné que ce germe est ubiquitaire dans l'environnement aqueux et colonise jusqu'à 15% des patients hospitalisés, la disparition de son réservoir endogène semble difficile. Cependant, cette étude démontre que son contrôle est possible dans l'environnement, notamment dans les robinets en augmentant la température de l'eau. De plus, si une souche multi-résistante est retrouvée de manière répétée dans l'environnement, des efforts doivent être mis en place pour éliminer cette souche. Des efforts doivent être également entrepris afin de limiter la transmission entre les patients, qui est une cause importante et récurrente de contamination exogène. - Pseudomonas aeruginosa is one of the leading nosocomial pathogens in intensive care units (ICUs). The source of this microorganism can be either endogenous or exogenous. The proportion of cases as a result of transmission is still debated, and its elucidation is important for implementing appropriate control measures. To understand the relative importance of exogenous vs. endogenous sources of P. aeru¬ginosa, molecular typing was performed on all available P. aeruginosa isolated from ICU clinical and environmental specimens in 1998, 2000, 2003, 2004 and 2007. Patient samples were classified according to their P. aeruginosa genotypes into three categories: (A) identical to isolate from faucet; (B) identical to at least one other patient sample and not found in faucet; and (C) unique genotype. Cases in cat¬egories A and Β were considered as possibly exogenous, and cases in category C as possibly endogenous. A mean of 34 cases per 1000 admissions per year were found to be colonized or infected by P. aeruginosa. Higher levels of faucet contamination were correlated with a higher number of cases in category A. The number of cases in category Β varied from 1.9 to 20 cases per 1000 admissions. This num¬ber exceeded 10/1000 admissions on three occasions and was correlated with an outbreak on one occasion. The number of cases con¬sidered as endogenous (category C) was stable and independent of the number of cases in categories A and B. The present study shows that repeated molecular typing can help identify variations in the epidemiology of P. aeruginosa in ICU patients and guide infection control measures.
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Sexual reproduction is extremely widespread in spite of its presumed costs relative to asexual reproduction, indicating that it must provide significant advantages. One postulated benefit of sex and recombination is that they facilitate the purging of mildly deleterious mutations, which would accumulate in asexual lineages and contribute to their short evolutionary life span. To test this prediction, we estimated the accumulation rate of coding (nonsynonymous) mutations, which are expected to be deleterious, in parts of one mitochondrial (COI) and two nuclear (Actin and Hsp70) genes in six independently derived asexual lineages and related sexual species of Timema stick insects. We found signatures of increased coding mutation accumulation in all six asexual Timema and for each of the three analyzed genes, with 3.6- to 13.4-fold higher rates in the asexuals as compared with the sexuals. In addition, because coding mutations in the asexuals often resulted in considerable hydrophobicity changes at the concerned amino acid positions, coding mutations in the asexuals are likely associated with more strongly deleterious effects than in the sexuals. Our results demonstrate that deleterious mutation accumulation can differentially affect sexual and asexual lineages and support the idea that deleterious mutation accumulation plays an important role in limiting the long-term persistence of all-female lineages.
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We analyze crash data collected by the Iowa Department of Transportation using Bayesian methods. The data set includes monthly crash numbers, estimated monthly traffic volumes, site length and other information collected at 30 paired sites in Iowa over more than 20 years during which an intervention experiment was set up. The intervention consisted in transforming 15 undivided road segments from four-lane to three lanes, while an additional 15 segments, thought to be comparable in terms of traffic safety-related characteristics were not converted. The main objective of this work is to find out whether the intervention reduces the number of crashes and the crash rates at the treated sites. We fitted a hierarchical Poisson regression model with a change-point to the number of monthly crashes per mile at each of the sites. Explanatory variables in the model included estimated monthly traffic volume, time, an indicator for intervention reflecting whether the site was a “treatment” or a “control” site, and various interactions. We accounted for seasonal effects in the number of crashes at a site by including smooth trigonometric functions with three different periods to reflect the four seasons of the year. A change-point at the month and year in which the intervention was completed for treated sites was also included. The number of crashes at a site can be thought to follow a Poisson distribution. To estimate the association between crashes and the explanatory variables, we used a log link function and added a random effect to account for overdispersion and for autocorrelation among observations obtained at the same site. We used proper but non-informative priors for all parameters in the model, and carried out all calculations using Markov chain Monte Carlo methods implemented in WinBUGS. We evaluated the effect of the four to three-lane conversion by comparing the expected number of crashes per year per mile during the years preceding the conversion and following the conversion for treatment and control sites. We estimated this difference using the observed traffic volumes at each site and also on a per 100,000,000 vehicles. We also conducted a prospective analysis to forecast the expected number of crashes per mile at each site in the study one year, three years and five years following the four to three-lane conversion. Posterior predictive distributions of the number of crashes, the crash rate and the percent reduction in crashes per mile were obtained for each site for the months of January and June one, three and five years after completion of the intervention. The model appears to fit the data well. We found that in most sites, the intervention was effective and reduced the number of crashes. Overall, and for the observed traffic volumes, the reduction in the expected number of crashes per year and mile at converted sites was 32.3% (31.4% to 33.5% with 95% probability) while at the control sites, the reduction was estimated to be 7.1% (5.7% to 8.2% with 95% probability). When the reduction in the expected number of crashes per year, mile and 100,000,000 AADT was computed, the estimates were 44.3% (43.9% to 44.6%) and 25.5% (24.6% to 26.0%) for converted and control sites, respectively. In both cases, the difference in the percent reduction in the expected number of crashes during the years following the conversion was significantly larger at converted sites than at control sites, even though the number of crashes appears to decline over time at all sites. Results indicate that the reduction in the expected number of sites per mile has a steeper negative slope at converted than at control sites. Consistent with this, the forecasted reduction in the number of crashes per year and mile during the years after completion of the conversion at converted sites is more pronounced than at control sites. Seasonal effects on the number of crashes have been well-documented. In this dataset, we found that, as expected, the expected number of monthly crashes per mile tends to be higher during winter months than during the rest of the year. Perhaps more interestingly, we found that there is an interaction between the four to three-lane conversion and season; the reduction in the number of crashes appears to be more pronounced during months, when the weather is nice than during other times of the year, even though a reduction was estimated for the entire year. Thus, it appears that the four to three-lane conversion, while effective year-round, is particularly effective in reducing the expected number of crashes in nice weather.
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[Quintessence] - L'incidence du mélanome malin augmente rapidement depuis plus de 50 ans. - La Suisse, avec 1700 nouveaux cas diagnostiqués par an, est, avec la Norvège, le pays d'Europe le plus touché par le mélanome. - Des différences régionales sont récemment apparues avec une incidence plus élevée dans les cantons romands. - Les changements observés en Suisse dans l'attitude et le comportement face au soleil sont trop récents et modestes pour influencer l'incidence. - La détection précoce effectuée depuis près de 20 ans a permis d'augmenter la survie et le taux de mélanomes fins sans toutefois altérer l'incidence des lésions épaisses. - La mortalité associée au mélanome malin a récemment diminué, d'abord chez les femmes. L'efficacité de la prévention devrait se confirmer à terme si les efforts entrepris se poursuivent. [Auteurs] [Summary] - The incidence of malignant melanoma has steadily increased in Caucasian populations over the last 50 years. - With some 1700 new cases per year, Switzerland has, with Norway, the highest rate of melanoma in Europe. - Regional differences within Switzerland are emerging, with a higher incidence in western (French-speaking) cantons. - Observed changes in sun protection attitudes and knowledge in the Swiss population have yet to impact on the incidence trend. - Early detection, as pursued since the mid-1980s in Switzerland, has led to a substantial increase in survival and rates of thin melanoma, without major change in rates of thick melanoma. - Mortality from melanoma has recently decreased, initially in women. The effectiveness of prevention campaigns should eventually be confirmed if current efforts persist. [Authors]
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We postulate a two-region world, comprised of North (calibrated after the US) and South(calibrated after China). Our optimization results show the compatibility of the following threedesiderata:(1) Global CO2 emissions follow a conservative path that leads to the stabilizationof concentrations at 450 ppm.(2) North and South converge to a path of sustained growth at 1% per year (28.2%per generation) in 2075.(3) During the transition to the steady state, North also grows at 1% per year whileSouth s rates of growth are markedly higher.The transition paths require a drastic reduction of the share of emissions allocated to North,large investments in knowledge, both in North and South, as well as very large investments ineducation in South. Surprisingly, in order to sustain North s utility growth rate, some output mustbe transferred from South to North during the transition.Although undoubtedly subject to many caveats, our results support a degree of optimism byproviding prima facie evidence of the possibility of tackling climate change in a way that is fairboth across generations and across regions while allowing for positive rates of humandevelopment.
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We investigated dispersal patterns in the monogamous Crocidura russula, based both on direct field observations (mark-recapture data) and on genetic analyses (microsatellite loci). Natal dispersal was found to be low. Most juveniles settled within their natal territory or one immediately adjacent. Migration rate was estimated to two individuals per year and per population. The correlation between genetic and geographical distances over a 16 km transect implies that migration occurs over short ranges. Natal dispersal was restricted to first-litter juveniles weaned in early May; this result suggests a direct dependence of dispersal on reproductive opportunities. Natal dispersal was highly female biased, a pattern unusual among mammals. Its association with monogamy provides support for the resource-competition model of dispersal. Our results demonstrate that a state-biased dispersal can be directly inferred from microsatellite genotype distributions, which opens new perspectives for empirical studies in this area.
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Introduction. Agricultural workers are among the professional groups most at risk of developing acute or chronic respiratory problems. Despite this fact, the etiology of these occupational diseases is poorly known, even in important sectors of agriculture such as the crops sector. Cereals can be colonized by a large number of fungal species throughout the plants' growth, but also during grain storage. Some of these fungi deliver toxins that can have a serious impact on human health when they are ingested via wheat products. Although International and European legislation on contaminants in food, including mycotoxins, include measures to ensure protection of public health by setting down the maximum levels for certain contaminants, the risks associated with the inhalation of such molecules during grain handling remains poorly documented. Goal of study. This project's objective was to characterize worker exposure to pathogenic, irritative or allergenic microorganisms and to identify the abiotic or biotic factors that reduce the growth of these microorganisms in crops. Indeed, the proliferation of microorganisms on wheat is dependent on temperature, rainfall and human disturbance (e.g. usage of tillage, addition of fungicides). A change in the concentration of these microorganisms in the substrate will directly result in a change in the concentration of aerosolized particles of the same microorganisms. Therefore, the exposure of worker to bioaérosols will also change. The Vaud region of Switzerland is a perfect region for conduct such a project as weather conditions vary and agricultural land management programs are divers at a small geographic scale. Methods. Bioaerosols and wheat dust have been sampled during wheat harvesting of summer 2010 at 100 sites uniformly distributed in the Vaud region that are representative of the different agriculture practices. Personal exposure has been evaluated for different wheat related activities: harvesting, grain unload, baling straw, the cleaning of harvesters and silos. Aerosols have been sampled at a rate of 2L/min between 15 min to 4 hours (t) on a 5m PVC filter for estimating the total dust inhaled, on gelatine filter for the identification and quantification of molds, and on a 0.45um polycarbonate filter for endotoxin quantification. Altitude, temperature and annual average rainfall were considered for each site. The physical and chemical characteristics of soils were determined using the methods in effect at Sol Council (Nyon). Total dust has been quantified following NIOSH 0500 method. Reactive endotoxine activity has been determined with Limulus Amebocyte Lysate Assay. All molds have been identified by the pyrosequencing of ITS2 amplicons generated from bioaerosol or wheat dust genomic DNA. Results & Conclusions. Our results confirm the previous quantitative data on the worker exposure to wheat dust. In addition, they show that crop workers are systematically exposed to complex mixtures of allergens, irritants or cytotoxic components. The novelty of our study is the systematic detection of molds such as Fusarium - that is a mycotoxins producer - in the bioaerosols. The results are interpreted by taking in account the agriculture practice, the Phosphorus : Carbon : Nitrogen ratio of the soil, the altitude and the average of rainy days per year.
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BACKGROUND: We assessed the prevalence of risk factors for cardiovascular disease (CVD) in a middle-income country in rapid epidemiological transition and estimated direct costs for treating all individuals at increased cardiovascular risk, i.e. following the so-called "high risk strategy". METHODS: Survey of risk factors using an age- and sex-stratified random sample of the population of Seychelles aged 25-64 in 2004. Assessment of CVD risk and treatment modalities were in line with international guidelines. Costs are expressed as USD per capita per year. RESULTS: 1255 persons took part in the survey (participation rate of 80.2%). Prevalence of main risk factors was: 39.6% for high blood pressure (> or =140/90 mmHg or treatment) of which 59% were under treatment; 24.2% for high cholesterol (> or =6.2 mmol/l); 20.8% for low HDL-cholesterol (<1.0 mmol/l); 9.3% for diabetes (fasting glucose > or =7.0 mmol/l); 17.5% for smoking; 25.1% for obesity (body mass index > or =30 kg/m2) and 22.1% for the metabolic syndrome. Overall, 43% had HBP, high cholesterol or diabetes and substantially increased CVD risk. The cost for medications needed to treat all high-risk individuals amounted to USD 45.6, i.e. 11.2 dollars for high blood pressure, 3.8 dollars for diabetes, and 30.6 dollars for dyslipidemia (using generic drugs except for hypercholesterolemia). Cost for minimal follow-up medical care and laboratory tests amounted to 22.6 dollars. CONCLUSION: High prevalence of major risk factors was found in a rapidly developing country and costs for treatment needed to reduce risk factors in all high-risk individuals exceeded resources generally available in low or middle income countries. Our findings emphasize the need for affordable cost-effective treatment strategies and the critical importance of population strategies aimed at reducing risk factors in the entire population.
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Silene dioica is a diploid, dioecious, perennial, insect-pollinated herb and part of the deciduous phase of primary succession in Skeppsvik Archipelago, Gulf of Bothnia, Sweden. These islands are composed of material deposited and left underwater by melting ice at the end of the last ice age. A rapid and relatively constant rate of land uplift of 0.9 cm per year continually creates new islands available for colonization by plants. Because the higher deposits appear first, islands differ in age. Because it is possible to estimate the ages of islands and populations of plant species belonging to early stages of succession, the genetic dynamics occurring within an age-structured metapopulation can be investigated in this archipelago. Fifty-two island populations of S. dioica of known ages, sizes, and distances from each other were studied through electrophoretic data. A number of factors increase the degree of genetic differentiation among these island populations relative to an island model at equilibrium. Newly founded populations were more differentiated than those of intermediate age, which suggests that colonization dynamics increase genetic variance among populations. The very old populations, which decrease in size as they approach extinction, were more differentiated than intermediate-aged populations. Isolation by distance occurs in this system. Colonizers are likely to come from more than one source, and the migrant pool model best explains colonization events in the archipelago. Degree of environmental exposure also affects population differentiation.