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An increasingly older population will most likely lead to greater demands on the health care system, as older age is associated with an increased risk of having acute and chronic conditions. The number of diseases or disabilities is not the only marker of the amount of health care utilized, as persons may seek hospitalization without a disease and/or illness that requires hospital healthcare. Hospitalization may pose a severe risk to older persons, as exposure to the hospital environment may lead to increased risks of iatrogenic disorders, confusion, falls and nosocomial infections, i.e., disorders that may involve unnecessary suffering and lead to serious consequences. Aims: The overall aim of this thesis was to describe and explore individual trajectories of cognitive development in relation to hospitalization and risk factors for hospitalization among older persons living in different accommodations in Sweden and to explore older persons' reasons for being transferred to a hospital. Methods: The study designs were longitudinal, prospective and descriptive, and both quantitative and qualitative methods were used. Specifically, latent growth curve modelling was used to assess the association of cognitive development with hospitalization. The Cox proportional hazards regression model was used to analyse factors associated with hospitalization risk overtime. In addition, an explorative descriptive design was used to explore how home health care patients experienced and perceived their decision to seek hospital care. Results: The most common reasons for hospitalization were cardiovascular diseases, which caused more than one-quarter of first hospitalizations among the persons living in ordinary housing and nursing home residents (NHRs). The persons who had been hospitalized had a lower mean level of cognitive performance in general cognition, verbal, spatial/fluid, memory and processing speed abilities compared to those who had not been hospitalized. Significantly steeper declines in general cognition, spatial/fluid and processing speed abilities were observed among the persons who had been hospitalized. Cox proportional hazards regression analysis showed that the number of diseases, number of drugs used, having experienced a fall and being assessed as malnourished according to the Mini Nutritional Assessment scale were related to an increased hospitalization risk among the NHRs. Among the older persons living in ordinary housing, the risk factors for hospitalization were related to marital status, i.e., unmarried persons and widows/widowers had a decreased hospitalization risk. In addition, among social factors, receipt of support from relatives was related to an increased hospitalization risk, while receipt of support from friends was related to a decreased risk. The number of illnesses was not associated with the hospitalization risk for older persons in any age group or for those of either sex, when controlling for other variables. The older persons who received home health care described different reasons for their decisions to seek hospital care. The underlying theme of the home health care patients’ perceptions of their transfer to a hospital involved trust in hospitals. This trust was shared by the home health care patients, their relatives and the home health care staff, according to the patients. Conclusions: This thesis revealed that middle-aged and older persons who had been hospitalized exhibited a steeper decline in cognition. Specifically, spatial/fluid, processing speed, and general cognitive abilities were affected. The steeper decline in cognition among those who had been hospitalized remained even after controlling for comorbidities. The most common causes of hospitalization among the older persons living in ordinary housing and in nursing homes were cardiovascular diseases, tumours and falls. Not only health-related factors, such as the number of diseases, number of drugs used, and being assessed as malnourished, but also social factors and marital status were related to the hospitalization risk among the older persons living in ordinary housing and in nursing homes. Some risk factors associated with hospitalization differed not only between the men and women but also among the different age groups. The information provided in this thesis could be applied in care settings by professionals who interact with older persons before they decide to seek hospital care. To meet the needs of an older population, health care systems need to offer the proper health care at the most appropriate level, and they need to increase integration and coordination among health care delivered by different care services.

Introdução: O excesso de peso em adultos jovens está associado ao desenvolvimento de doenças crônicas não transmissíveis (DCNT) e à diminuição da qualidade de vida e ao aumento da mortalidade precoce. A transição da adolescência para a fase adulta é o período de maior risco para a incidência da obesidade. Objetivo: Estimar o efeito o índice de massa corpora (IMC) aos 20 anos sobre a incidência de DCNT em adultos brasileiros com idade entre 30 a 49 anos. Métodos: Foram selecionados 12.079 indivíduos de 30 a 49 anos da Pesquisa Nacional de Saúde (PNS), realizada no ano de 2013. O modelo adotado para determinação das DCNT foi aquele proposto pela Organização Mundial de Saúde. A incidência das DCNT (hipertensão, doenças cardiovasculares, diabetes e câncer, entre outras), informada pela data do diagnóstico, foi modelada como função do IMC aos 20 anos. Os indivíduos sem a doença até o presente foram considerados como censura. As estimativas de sobrevida foram calculadas com o método de Kaplan-Meier (KM) para cada uma das doenças, estratificada por sexo e ajustada por escolaridade. A análise dos fatores de risco para as doenças foi feita utilizando-se o modelo de riscos proporcionais de Cox. Resultados: Nas curvas de sobrevida KM, indivíduos com IMC >=25kg/m² apresentaram incidência mais elevada e precoce de DCNT, principalmente hipertensão, diabetes e depressão. A idade mediana para incidência do diabetes em obesos foi de 47 anos para homens e 48 anos para mulheres. A incidência da hipertensão arterial foi 4,2 por mil com sobrevida mediana de 48 e 44 anos em mulheres com excesso de peso e obesidade, respectivamente. Dentre os fatores de risco associados as DCNT, o tabagismo em idade precoce foi associado à incidência de depressão. Conclusão: O excesso de peso em adultos jovens aumenta a incidência precoce de DCNT, com efeitos negativos na qualidade de vida, lazer e produtividade, além de aumentar a demanda por serviços de saúde. Torna-se necessário que a intervenção para redução dessas doenças seja direcionada para o período da infância e adolescência com ações que promovam a redução da exposição desses indivíduos à alimentação de má qualidade e incentivo a prática de atividade, não uso do tabaco e consumo moderado de álcool. / Introduction: Overweight in young adults is associated with the development of chronic noncommunicable diseases (NCDs) and decreased quality of life and increased early mortality. The transition from adolescence to adulthood is the period of greatest risk for the incidence of obesity. Objective: To estimate the effect of the corpora mass index (BMI) at age 20 on the incidence of NCDs in Brazilian adults aged 30-49 years. Methods: We selected 12 079 individuals 30-49 years of the National Health Research (PNS) held in 2013. The model adopted for determining the NCD was that proposed by the World Health Organization The incidence of NCDs (hypertension, diseases. cardiovascular, diabetes and cancer, among others), informed by the date of diagnosis, and modeled as a function of BMI at age 20. Individuals without the disease to date have been considered as censorship. Survival estimates calculated with the Kaplan-Meier (KM) for each of the diseases, stratified by gender and adjusted for schooling. The analysis of risk factors for the disease made using the model of Cox proportional hazards. Results: In the survival curves KM, individuals with BMI> = 25 kg / m² presented higher and early incidence of NCDs, particularly hypertension, diabetes and depression. The median age for incidence of diabetes in obese was 47 years for men and 48 years for women. The incidence of hypertension was 4.2 per thousand with a median survival of 48 and 44 years in women with excess weight and obesity respectively. Among the risk factors associated with the NCD, smoking at an early age was associated with the incidence of depression. Conclusion: Being overweight in young adults increases the early incidence of NCDs, with negative effects on quality of life, leisure and productivity, and increase the demand for health services. It is necessary that the intervention to reduce these diseases directed to the period of childhood and adolescence with actions that promote a reduction in exposure of these individuals to the poor quality of food and encouraging the practice of activity, no tobacco use and moderate consumption alcohol.

<p>A general time-to-event data analysis known as event history analysis is considered. The focus is on the analysis of time-to-event data using Cox's regression model when the time to the event may be measured from different origins giving several observable time scales and when longitudinal measurements are involved. For the multiple time scales problem, procedures to choose a basic time scale in Cox's regression model are proposed. The connections between piecewise constant hazards, time-dependent covariates and time-dependent strata in the dual time scales are discussed. For the longitudinal measurements problem, four methods known in the literature together with two proposed methods are compared. All quantitative comparisons are performed by means of simulations. Applications to the analysis of infant mortality, morbidity, and growth are provided.</p>

<p>This thesis consists of four papers about the assumption of proportional hazards for the Cox model in survival analysis. </p><p>The <b>first paper </b>compares the hazard ratio estimated from the Cox model to an exact calculation of the geometric average of the hazard ratio when the underlying assumption of proportional hazards is false, i.e. when the hazards are not proportional. The estimates are evaluated in a simulation study.</p><p>The <b>second paper</b> describes and compares six of the most common numerical procedures to check the assumption of proportional hazards for the Cox model. The tests are evaluated in a simulation study.</p><p>Six graphical procedures to check the same assumption of proportional hazards for the Cox model are described and compared in the <b>third paper</b>. A criterion for rejection is derived for each procedure, to make it possible to compare the results of the different methods. The procedures are evaluated in a simulation study.</p><p>In the <b>fourth paper </b>the effects of covariate measurement error on testing the assumption of proportional hazards is investigated. Three of the most common numerical procedures to check the assumption of proportional hazards for the Cox model are evaluated in a simulation study. </p>

This thesis consists of four papers about the assumption of proportional hazards for the Cox model in survival analysis. The <b>first paper </b>compares the hazard ratio estimated from the Cox model to an exact calculation of the geometric average of the hazard ratio when the underlying assumption of proportional hazards is false, i.e. when the hazards are not proportional. The estimates are evaluated in a simulation study. The <b>second paper</b> describes and compares six of the most common numerical procedures to check the assumption of proportional hazards for the Cox model. The tests are evaluated in a simulation study. Six graphical procedures to check the same assumption of proportional hazards for the Cox model are described and compared in the <b>third paper</b>. A criterion for rejection is derived for each procedure, to make it possible to compare the results of the different methods. The procedures are evaluated in a simulation study. In the <b>fourth paper </b>the effects of covariate measurement error on testing the assumption of proportional hazards is investigated. Three of the most common numerical procedures to check the assumption of proportional hazards for the Cox model are evaluated in a simulation study.

A general time-to-event data analysis known as event history analysis is considered. The focus is on the analysis of time-to-event data using Cox's regression model when the time to the event may be measured from different origins giving several observable time scales and when longitudinal measurements are involved. For the multiple time scales problem, procedures to choose a basic time scale in Cox's regression model are proposed. The connections between piecewise constant hazards, time-dependent covariates and time-dependent strata in the dual time scales are discussed. For the longitudinal measurements problem, four methods known in the literature together with two proposed methods are compared. All quantitative comparisons are performed by means of simulations. Applications to the analysis of infant mortality, morbidity, and growth are provided.

Chronic wasting disease (CWD) has infected wild deer of Saskatchewan for at least the past 10 years. Disease management plans have evolved over the years, but without information on mule deer (<i>Odocoileus hemionus</i>) habits and movements in the grasslands of southern Saskatchewan. We radio-collared and monitored the survival and movements of 206 mule deer from 2006 to 2009. Long distance movements by deer have potential to transfer disease to previously naïve areas. Survival rates had not yet been evaluated in this area; baseline data will provide a useful measure for population-level impacts of the disease in the future.<p> Juvenile dispersals and adult migrations were contrasted from 4 study areas along the South Saskatchewan River. Dispersal distance (median = 22.8 km, n = 14) was similar to migration distance (median = 16.0 km, n = 49). Median migration distance was similar between males (15.7 km, n = 51) and females (19.7 km, n = 65). Obligatory migrants were more likely to be female. Deer from an area of extensive grassland were more likely to be migratory than their counterparts in fragmented grassland of an agricultural landscape. Maximum migration and dispersal distances were 113 km and 195 km, respectively. Movement paths of 33 GPS-collared deer were best explained by high terrain ruggedness values and proximity to grassland.<p> Seasonal survival rates showed that deer had lowest survival in autumn months during hunting season. Juveniles had lower survival than adults in all seasons. Harvest regime changes in 2008 improved the autumn survival of adult females but adult males had lower survival than in 2007. Body condition of captured deer was evaluated from residuals of mass-length regression. Cox regression analyses suggested that deer in good body condition (75th percentile) were half as likely to die and that those in very poor body condition (10th percentile) were twice as likely to die. Radio collars that weighed > 2% of body mass negatively affected survival and we recommend future researchers take this into consideration. <p> Survival, dispersal, and migration rates and patterns are crucial parameters in modeling CWD in local mule deer populations. Saskatchewan wildlife managers aim to prevent CWD spread into new areas, and can use mule deer movement orientations to target surveillance accordingly. White-tailed deer (<i>Odocoileus virginianus</i>) movements are briefly discussed; further knowledge of their movements is required for CWD management in all of Saskatchewan.

Chronic wasting disease (CWD) has infected wild deer of Saskatchewan for at least the past 10 years. Disease management plans have evolved over the years, but without information on mule deer (<i>Odocoileus hemionus</i>) habits and movements in the grasslands of southern Saskatchewan. We radio-collared and monitored the survival and movements of 206 mule deer from 2006 to 2009. Long distance movements by deer have potential to transfer disease to previously naïve areas. Survival rates had not yet been evaluated in this area; baseline data will provide a useful measure for population-level impacts of the disease in the future.<p> Juvenile dispersals and adult migrations were contrasted from 4 study areas along the South Saskatchewan River. Dispersal distance (median = 22.8 km, n = 14) was similar to migration distance (median = 16.0 km, n = 49). Median migration distance was similar between males (15.7 km, n = 51) and females (19.7 km, n = 65). Obligatory migrants were more likely to be female. Deer from an area of extensive grassland were more likely to be migratory than their counterparts in fragmented grassland of an agricultural landscape. Maximum migration and dispersal distances were 113 km and 195 km, respectively. Movement paths of 33 GPS-collared deer were best explained by high terrain ruggedness values and proximity to grassland.<p> Seasonal survival rates showed that deer had lowest survival in autumn months during hunting season. Juveniles had lower survival than adults in all seasons. Harvest regime changes in 2008 improved the autumn survival of adult females but adult males had lower survival than in 2007. Body condition of captured deer was evaluated from residuals of mass-length regression. Cox regression analyses suggested that deer in good body condition (75th percentile) were half as likely to die and that those in very poor body condition (10th percentile) were twice as likely to die. Radio collars that weighed > 2% of body mass negatively affected survival and we recommend future researchers take this into consideration. <p> Survival, dispersal, and migration rates and patterns are crucial parameters in modeling CWD in local mule deer populations. Saskatchewan wildlife managers aim to prevent CWD spread into new areas, and can use mule deer movement orientations to target surveillance accordingly. White-tailed deer (<i>Odocoileus virginianus</i>) movements are briefly discussed; further knowledge of their movements is required for CWD management in all of Saskatchewan.

The main aim of this study is to explore the effects of risk factors contributing to death in the elderly American population. To achieve this purpose, we constructed Cox proportional hazard regression models and logistic regression models with the complex survey dataset from the national Second Longitudinal Study of Aging (LSOA II) to calculate the hazard ratios (HR)/odds ratios (OR) and confidence interval (CI) of risk factors. Our results show that in addition to chronic disease conditions, many risk factors, such as demographic factors (gender and age), social factors (interaction with friends or relatives), personal health behaviors (smoking and exercise), and biomedical factors (Body mass index and emotional factors) have significant effects on death in the elderly American population. This will provide important information for elderly people to prolong lifespan regardless of whether they have chronic disease/diseases or not.