Health and Individual and Community Characteristics: A Research Protocol

Population health policies tend to target communities to enhance the health status of individuals. However, little is known about the effects of community or socio-economic environmental variables on individual health characteristics and behaviour patterns. This paper outlines procedures designed to examine the contribution of context in producing health.health policy

Unemployment and Health: Contextual Level Influences on the Production of Health in Populations

While there is a large and growing literature investigating the relationship between an individuals' employment status and his or her health, considerably less is known about the effect on this relationship of the context in which unemployment occurs. The aim of this paper is to test for the presence and nature of contextual effects in the ways unemployment and health are related, based on a simple underlying model of stress, social support and health using a large population health survey. An individual's health can be influenced directly by own exposure to unemployment and by exposure to unemployment in the individual's context, and indirectly by the effects these exposures have on the relationship between other health determinants and health. Based on this conceptualization an empirical model, using multi-level analysis, is formulated that identifies a five -stage process for exploring these complex pathways through which unemployment affects health. Results showed that the association of individual unemployment with perceived health is statistically significant. Nevertheless, this study did not provide evidence to support the hypothesis that the association of unemployment with health status depends upon whether the experience of unemployment is shared with people living in the same environment.. Above all, this study demonstrates both the subtlety and complexity of individual and contextual level influences on the health of individuals. Our results caution against simplistic interpretations of the unemployment-health relationship and reinforce the importance of using multi-level statistical methods for investigation of it.Unemployment, population health, contextual effect, multi-level models, survey data set, census data set

Use of Help by the Elderly: A Gender Issue?

The routine of instrumental activities of daily living is dependent on the living arrangement of the elderly person in the sense that the availability of a co-resident increases the opportunities for sharing the responsibility for the performance of these activities. However, women are at a higher risk than men to be widowed and to live alone. Thus, the availability of caregivers within the household may be lower for females than for males elderly. As a consequence, gender may appear as a confounder in the relationship between the use of help and the location of the caregiver within or outside the elderly person household. A correspondence analysis was run on a sample of elderly persons living in the community to examine this issue. The results of the analysis showed that elderly women rely predominantly on caregivers living outside of their home for the performance of nine activities reviewed in this study, while males rely predominantly on caregivers located within their household. Nevertheless, 20& of males and females assumed responsibility for the nine activities reviewed in this study while 15% of females relied on a resident for some of the activities and 15% of males relied on a non-resident. This study confirmed that caregivers are shouldering responsibilities for activities. But this help is not structured in the same way for elderly males and elderly females with importance consequences for policy. For example, 30% of the elderly with a non-resident caregiver wished to live in a senior housing project in this study, while 17% expressed this wish among those with a resident caregiver. There is some scattered research evidence that the behavior of elderly males and females toward use of formal and informal help for activities of daily living differs. These gender differences may depend in part on health status, division of household labour and links with family and friends. These factors may affect not only the availability of help, but also the sources of help. If this is the case, use of help is structured differently for male and for female elderly. We argue in this paper that differences in sources of help for male and female elderly have wide ranging implications for a better understanding of the role of informal support for the elderly and for links between informal and formal sources of help.

The utilization of health services : Sequence of visits to general practitioners

Multivariate studies of health services utilization have been particularly disappointing. Some of the difficulties might be within the conceptualization of the utilization concept. The purpose of this paper is to suggest that propensity to utilize should be expressed in time sequences and that an explanation should be sought for such sequences, rather than for the total number of times physicians are consulted. Using data from the universal health insurance scheme in Québec, the concept of sequence of visits is illustrated, while variations in utilization patterns are better explained by the sequences of utilization than by age and sex.

Impact on Cronbach's alpha of simple treatment methods for missing data

The scientific treatment of missing data has been the subject of research for nearly a century. Strangely, interest in missing data is quite new in the fields of educational science and psychology (Peugh & Enders, 2004; Schafer & Graham, 2002). It is now important to better understand how various common methods for dealing with missing data can affect well-used psychometric coefficients. The purpose of this study is to compare the impact of ten common fill-in methods on Cronbachs alpha (1951). We use simulation studies to investigate the behavior of alpha in various situations. Our results show that multiple imputation is the most effective method. Furthermore, simple imputation methods like Winer imputation, item mean, and total mean are interesting alternatives for specific situations. These methods can be easily used by non-statisticians such as teachers and school psychologists

Abstract tree crowns in 3D radiative transfer models: Impact on simulated open-canopy reflectances

Three-dimensional (3D) radiative transfer models of vegetation canopies are increasingly used to study the reflective properties of specific land cover types and to interpret satellite-based remote sensing observations of such environments. In doing so, most 3D canopy reflectance models simplify the structural representation of individual tree crowns, for example, by using a single ellipsoidal envelope or a series of cubic volumes (known as voxels) to approximate the actual crown shape and the 3D distribution of scatterers therein. Often these tree abstractions ignore or simplify the woody architectures as well. Focusing on broad-leafed Savanna trees, this study investigates the impact that architectural simplifications may have on the fidelity of simulated satellite observations at the bottom-of-the-atmosphere for a variety of spatial resolutions, spectral bands, as well as, viewing and illumination geometries. As quality objective for the simulated bidirectional reflectance factors (BRFs) the typical uncertainty associated with vicarious calibration efforts is used, i.e., 5%. Our results indicate that the size of the voxel as well as the spectral, viewing, and illumination conditions drive the BRF bias at a given spatial resolution. The simulation of remote sensing data at medium spatial resolution is not affected by canopy abstractions except in the NIR for cases where woody structures are completely omitted. Here the BRF simulations of the abstract tree crowns exceeded the 5% tolerance limit even at spatial resolutions coarser than 100m. For high resolution satellite imagery, i.e. for nominal pixel sizes of 1×1 m2 or finer, BRF biases in excess of ±50% can occur within individual tree crowns and/or inside their shadows on the background. The sign of the local BRF bias is determined by the relative weight of the single-uncollided and single-collided BRF components.JRC.H.7-Climate Risk Managemen

Estimating leaf area distribution in savanna trees from terrestrial LiDAR measurements

Vegetation structure parameters are key elements in the study of ecosystem functioning and global scale ecosystemic interactions. The detailed retrieval of many of these parameters by direct measurements is impractical due to the quantity of plant material in trees. Terrestrial LiDAR Scanners (TLSs) have been shown to hold great potential as an indirect means of estimating plant structure parameters with a high level of detail, while some studies identified a number of challenges inherent to this approach. In this study we investigate the use of a voxel-based approach to retrieve leaf area distribution of individual trees. The approach is based on the contact frequency method applied to co-registered TLS returns from two or more scanning positions. The contact frequency was computed for voxels being 10, 30, and 50 cm in size and subsequently corrected for the influence of occlusion effects, leaf inclination, the presence of non-photosynthetic material, and the laser beam size. The leaf area of voxels for which occlusion effects were too pronounced was estimated using modeled values based on the availability of light. We compared the TLS derived leaf area estimates against direct measurements, obtained by the harvesting of leaves, in a broad-leaved savanna of central Mali. The measured leaf area values of the sampled trees ranged from 30 to 530 m2, and crown LAI values between 0.8 and 7.2. The leaf area estimates lay on average 14% from the reference measurements (general bias). Our method provides vertical as well as radial distributions of leaf area in individual trees, and lends itself to the estimation of savanna vegetation structural parameters with a high level of detail.JRC.H.3-Global environment monitorin