Healthcare utilization and costs among older adult female drivers and former drivers

PurposeThis study compared the healthcare utilization and costs for specific types of medical services among older adult women who currently drive and those who no longer drive.MethodsThis study included 347 women aged 65 or older who were either former (had stopped driving) or current drivers, randomly sampled from a large U.S. health plan to participate in a telephone survey, and who had automated health records with healthcare utilization and cost data. Bivariate analyses and generalized linear modeling were used to examine associations between driving status and healthcare utilization and costs.ResultsAdjusting for age, income, and marital status, former drivers were more likely than current drivers to use mental health care services (RR = 3.37; 95% CI: 1.03, 10.98). Former drivers also tended to use more inpatient (RR = 1.85; 95% CI: 0.88, 3.87) and emergency services (RR = 1.89; 95% CI: 0.96, 3.70), but results did not reach statistical significance. Total annual healthcare costs in 2005 were almost twice as high for former drivers compared with current drivers ($13,046 vs. $7,054; mean difference = $5,992; 95% CI: -$360, $12,344), although this relationship was not statistically significant (CR = 1.61; 95% CI: 0.88, 2.96).Impact on IndustryFormer drivers were more than three times as likely as current drivers to use mental health services, and tended to use more emergency and inpatient services. Further research on factors that potentially mediate the relationship between driving status and health service use is warranted.     

Temporal variance of disturbance did not affect diversity and structure of a marine fouling community in north-eastern New Zealand

Natural heterogeneity in ecological parameters, like population abundance, is more widely recognized and investigated than variability in the processes that control these parameters. Experimental ecologists have focused mainly on the mean intensity of predictor variables and have largely ignored the potential to manipulate variances in processes, which can be considered explicitly in experimental designs to explore variation in causal mechanisms. In the present study, the effect of the temporal variance of disturbance on the diversity of marine assemblages was tested in a field experiment replicated at two sites on the northeast coast of New Zealand. Fouling communities grown on artificial settlement substrata experienced disturbance regimes that differed in their inherent levels of temporal variability and timing of disturbance events, while disturbance intensity was identical across all levels. Additionally, undisturbed assemblages were used as controls. After 150 days of experimental duration, the assemblages were then compared with regard to their species richness, abundance and structure. The disturbance effectively reduced the average total cover of the assemblages, but no consistent effect of variability in the disturbance regime on the assemblages was detected. The results of this study were corroborated by the outcomes from simultaneous replicate experiments carried out in each of eight different biogeographical regions around the world.     

A Comparison of Corridors and Intrinsic Connectivity to Promote Dispersal in Transient Successional Landscapes

Low-vagility organisms that specialize on transitory successional habitats may be especially dependent upon habitat connectivity to maintain population viability. We analyzed the theoretical intrinsic connectivity of successional landscapes (i.e., the natural juxtaposition of similar habitats that allows dispersal) as a function of patch geometry coupled with the disperser's habitat specificity. Habitat specialists living in poorly connected landscapes (approximating hexagonal patches) have only a 26.5% chance of colonizing a new site when their resident patch becomes unsuitable. In contrast, generalists living in well connected landscapes can virtually always colonize a new site when needed. We infer from our simulation that for some habitat specialists, such as the rare, endemic Florida scrub lizard (Sceloporus woodi), anthropogenic control of successional dynamics for commercial logging may significantly reduce intrinsic connectivity. Lizard population viability may now depend upon the extrinsic connectivity provided by artificial corridors. However, the use of corridors will not serve as a general solution to the problem of anthropogenically reduced intrinsic connectivity until key logistical design problems have been resolved. Moreover, efforts to enhance intrinsic connectivity by modifying patch geometry may produce undesirable edge effects and conflict with old-growth preservation. Future research should focus on developing spatially explicit corridor models, documenting natural levels of intrinsic connectivity, quantifying anthropogenic disruption of natural connectivity, and describing species-specific mechanisms of inter-patch dispersal.     

Toxic phytoplankton blooms in the southwestern Gulf of Maine: testing hypotheses of physical control using historical data

Blooms of the toxic dinoflagellate Alexandrium tamarense Lebour have been nearly annual features along the coasts of southern Maine, New Hampshire and Massachusetts, USA, since 1972. In 1990 two hypotheses which have been used to explain the initiation of these blooms in the southwestern portion of the Gulf of Maine were tested using historical records of shellfish toxicity, wind, and river flow. The first hypothesis states that the blooms were initiated or advected to shore by wind-driven coastal upwelling. The second states that established blooms were advected from north to south alongshore in a coastally trapped buoyant plume of water. Of the eleven years examined (1979 to 1989), we found seven cases inconsistent with the wind-driven upwelling hypothesis, and only one case (1985) which contradicts the plume-advection hypothesis. 1985 was an unusual year in many respects, and we suggest that some other mechanism was responsible for the toxic outbreaks. In addition, the wind-driven upwelling hypothesis could not explain the observed north-to-south temporal progression of toxicity each year. The plume-advection hypothesis was found to best explain the datails of the timing and spread of shellfish toxicity in Gulf of Maine waters to the south of Penobscot Bay, Maine. These include the variable north-to-south progression with time, the presence of a toxin-free zone south of Cape Ann, Massachusetts, the sporadic nature of toxic outbreaks south of Massachusetts Bay, and the apparently rare occurrence of high toxicity levels well offshore on Nantucket Shoals and Georges Bank.     

Role of glutamine synthetase in ammonia assimilation by symbiotic marine dinoflagellates (zooxanthellae)

The dinoflagellate symbionts (zooxanthellae) present in many reef corals aid in the survival of the symbiotic unit in nitrogen deficient tropical waters by providing additional routes of nitrogen uptake and metabolism. The enzymatic pathway of ammonia assimilation from seawater and the re-assimilation of coral ammonium waste by zooxanthellae was studied by examining the affinity of glutamine synthetase for one of its substrates, ammonia. Glutamine synthetase activity was measured in dinoflagellates of the species Symbiodinium microadriaticum found in symbiotic association with various marine coelenterates. Michaelis-Menten kinetics for the substrate ammonia were determined for freshly isolated dinoflagellates from Condylactis gigantea (apparent NH₃ K_m=33 M) and for cultured dinoflagellates from Zoanthus sociatus (apparent NH₃ K_m=60 M). On the basis of the low apparent K_ms for NH₃, it appears that ammonia assimilation by these symbiotic dinoflagellates occurs via the glutamine synthetase/glutamate synthase pathway. Additionally, the uptake of exogenous ammonium by an intact coelenterate-dinoflagellate symbiosis was strongly inhibited by 0.5 mM methionine sulfoximine, and inhibitor of glutamine synthetase.     

Modelling gas release event behaviour in hazardous waste tanks

Certain radioactive waste storage tanks at the United States Department of Energy Hanford facilities continuously generate gases as a result of radiolysis and chemical reactions. The congealed sludge in these tanks traps the gases beneath it and causes the level of the waste within the tanks to rise. The waste level continues to rise until the sludge loses its buoyancy and rolls over, changing places with fluid on top. During a rollover, the trapped gases are released, resulting in a sudden drop in the waste level. This is known as a gas release event (GRE). After a GRE, the waste re-congeals and gas again accumulates, leading to another GRE. We are interested in the time between consecutive GREs. Understanding the probabilistic behaviour of the time between consecutive GREs is important because the hydrogen and nitrous oxide gases released during a GRE are flammable and the ammonia that is released is a health risk. From a safety perspective, activity around such waste tanks should be halted when a GRE is imminent. With a credible probability model for the time between consecutive GREs, we can establish time windows in which waste tank research and maintenance activities can be safely performed. We discuss the application of non-linear time series models to this problem.     

Quantifying effects of pollution on biodiversity: a case study of highly diverse molluscan assemblages in the Mediterranean

Structured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cm×20 cm quadrats were taken from each of three sites (80 m–100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m–4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H′) was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (Δ*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities.     

Influence of an artificial reef on the surrounding infaunal community

Artificial reefs have been constructed throughout the world, but their effects on adjacent soft-bottom communities are largely unknown. In December 1986, we investigated the influence of Pendleton Artificial Reef (PAR) in Southern California on the abundance of infauna in the surrounding sand bottom. PAR was constructed in 1980 of quarry rock placed in eight piles, or modules. The artificial reef altered the grain-size distribution of sediments around the reef; sediments close to the modules were coarser than those 10 or 20 m away from the modules. Densities of one of the two most common species, the polychaetePrionospio pygmaeus, were lower near the reef, perhaps due to foraging by reef-associated predators or because the habitat near the reef was less suitable. We found no evidence that foraging by reef-associated fishes caused a widespread reduction in infaunal densities near the reef, and in fact the other most common taxon,Spiophanes spp., had higher densities near the reef. The most conspicuous effect of the artificial reef concerned the tube-dwelling wormDiopatra ornata, which only occurred in close association with the modules. In addition, total infaunal density and the densities of decapods, echinoderms and sipunculids were higher withinD. ornata beds than outside the beds. These results indicate that the densities of some species were enhanced, and others depressed, around the reef, but that the overall effect of the artificial reef on the surrounding infauna was limited to a small area near the modules.     

The effects of varied dissolved oxygen concentrations and temperature on the wood-boring isopod genus Limnoria

Three species of the marine wood-boring genus Limnoria were subjected to low dissolved oxygen concentrations at different temperatures under laboratory conditions. 28-day median tolerance limits (TL_m) were 1.0 mg/l of dissolved oxygen at 15° to 16°C and 19° to 20°C for L. lignorum, 0.75 and 0.60 mg/l at 15° to 16°C and 22° to 25°C, respectively, for L. quadripunctata, and 1.0 and 1.18 mg/l at 15° to 16°C and 22° to 25°C, respectively, for L. tripunctata. The amount of burrowing activity, as measured by the egestion rate, was directly related to the amount of dissolved oxygen. A daily egestion rate of 0.116 mg per day in L. tripunctata at 22° to 25°C was the highest figure measured. The daily egestion rate was sharply reduced at dissolved oxygen concentrations below 3.0 mg/l.