Associations between physical activity, television viewing and postnatal depressive symptoms amongst healthy primiparous mothers

Background: Postnatal depression is a serious illness in new mothers. In the general population, physical activity (PA) has been found to reduce the risk of depression, whilst sedentary behaviour (SB; in particular television viewing) has been linked to higher levels of depressive symptoms, yet little is known regarding associations between PA, SB and postnatal depression. This study aimed to investigate associations between PA, television viewing and postnatal depressive symptoms in healthy primiparous mothers.. Methods: Cross-sectional survey data were provided by 406 first-time mothers (approximately 3-months postpartum) enrolled in the Melbourne InFANT Extend trial (2012/2013). Women self-reported PA (time spent walking for leisure and transport, and other moderate and vigorous PA), television viewing, and depressive symptoms (CES-D 10). Random intercept linear models examined associations between PA, television viewing and depressive symptoms. Results: In crude models total PA was inversely associated with risk of postnatal depressive symptoms (B = -0.122; 95% CI = -0.24, -0.01). In models adjusted for key sociodemographic and behavioural covariates the association did not remain statistically significant. No other associations between PA, television viewing and postnatal depressive symptoms were evident.. Conclusions: Postnatal depressive symptoms may not be related to PA and television viewing in the same way that these behaviours predict depressive symptoms in the general population. Further investigation of the specific domains of PA, as well as different types/contexts of SB and their respective associations with postnatal depressive symptoms is warranted in order to better inform development of targeted interventions aimed at enhancing postnatal mental health..

Assessing mediators between discrimination, health behaviours and physical health outcomes: a representative cross-sectional study

PURPOSE: Discrimination is a social determinant of health; however, the pathways linking discrimination to ill-health are under-researched. This study investigated the mediators through which discrimination affects health behaviours and physical health outcomes, as well as assessed whether sex moderated these mechanisms. METHODS: Data from a representative survey (n = 1023) of undergraduate students enrolled in a Brazilian university in 2012 were used. Structural equation models were applied to assess the following mediation mechanisms--(1) discrimination influences self-rated health and body mass index via anxiety/depression; (2) discrimination affects behaviours (alcohol consumption, problem drinking, smoking, fruit/vegetable consumption, and physical activity) through discomfort associated with discriminatory experiences. The potential of sex to act as an effect-modifying variable was also explored in each of the postulated pathways. RESULTS: The effect of discrimination on self-rated poor health was totally (100.0%) mediated by anxiety/depression, while body mass index was not correlated with discrimination. Self-reported discrimination was associated with some behaviours via discomfort. Particularly, discomfort partially mediated the positive association between discrimination, leisure time physical activity (43.3%), and fruit/vegetable consumption (52.2%). Sex modified the association between discrimination, discomfort and physical activity in that such mechanism (more discrimination → more discomfort → more physical activity) was statistically significant in the entire sample and among females, but not among males. CONCLUSIONS: This is one of the first studies to demonstrate that discrimination is associated with physical health outcomes and behaviours via distinct pathways. Future investigations should further explicate the mediational pathways between discrimination and key health outcomes.

Obesity management: Australian general practitioners' attitudes and practices

Objectives: To document general practitioners’ (GPs) attitudes and practices regarding the prevention and management of overweight and obesity.

Research Methods and Procedures: A cross-sectional survey of a randomly selected sample of 1500 Australian GPs was conducted, of which 752 questionnaires were returned. The measures included views on weight management, definitions of success, views regarding the usefulness of drugs, approaches to and strategies recommended for weight management, and problems and frustrations in managing overweight and obesity.

Results: GPs view weight management as important and feel they have an important role to play. Although they consider themselves to be well prepared to treat overweight patients, they believe that they have limited efficacy in weight management and find it professionally unrewarding. GPs view the assessment of a patient's dietary and physical activity habits and the provision of dietary and physical activity advice as very important. The approaches least likely to be considered important and/or least likely to be practiced were those that would support the patient in achieving and maintaining lifestyle change.

Discussion: There remains considerable opportunity to improve the practice of GPs in their management of overweight and obesity. Although education is fundamental, it is important to acknowledge the constraints of the GPs’ existing working environment.

24-h urinary sodium excretion is associated with obesity in a cross-sectional sample of Australian schoolchildren

Emerging evidence indicates that dietary Na may be linked to obesity; however it is unclear whether this relationship is independent of energy intake (EI). The aim of this study was to assess the association between Na intake and measures of adiposity, including BMI z score, weight category and waist:height ratio (WHtR), in a sample of Australian schoolchildren. This was a cross-sectional study of schoolchildren aged 4-12 years. Na intake was assessed via one 24-h urine collection. BMI was converted to age- and sex-specific z scores, and WHtR was used to define abdominal obesity. In children aged ≥8 years, EI was determined via one 24-h dietary recall. Of the 666 children with valid urine samples 55 % were male (average age 9·3 (sd 1·8) years). In adjusted models an additional 17 mmol/d of Na was associated with a 0·10 higher BMI z score (95 % CI 0·07, 0·13), a 23 % (OR 1·23; 95 % CI 1·16, 1·31) greater risk of being overweight/obese and a 15 % (OR 1·15; 95 % CI 1·09, 1·23) greater risk of being centrally obese. In the subsample of 8-12-year-old children (n 458), adjustment for EI did not markedly alter the associations between Na and adiposity outcomes. Using a robust measure of daily Na intake we found a positive association between Na intake and obesity risk in Australian schoolchildren, which could not be explained by total energy consumption. To determine whether this is a causal relationship, longitudinal studies, with high-quality measures of Na and EI, are required.

The association between self-reported diet quality and health-related quality of life in rural and urban Australian adolescents

OBJECTIVE: This study examines the relationship between diet quality and health-related quality of life (HRQoL) in rural and urban Australian adolescents, and gender differences.

DESIGN: Cross-sectional.

SETTING: Secondary schools.

PARTICIPANTS: 722 rural and 422 urban students from 19 secondary schools.

MAIN OUTCOME MEASURES: Self-report dietary-related behaviours, demographic information, HRQoL (AQoL-6D) were collected. Healthy and unhealthy diet quality scores were calculated; multiple linear regression investigated associations between diet quality and HRQoL.

RESULTS: Compared to urban students, rural students had higher HRQoL, higher healthy diet score, lower unhealthy diet score, consumed less soft drink and less frequently, less takeaway and a higher proportion consumed breakfast (P < 0.05). Overall, males had higher unhealthy diet score, poorer dietary behaviours but a higher HRQoL score compared to females (P < 0.05). In all students, final regression models indicated: a unit increase in healthy diet score was associated with an increase in HRQoL (unstandardised coefficient(B)±standard error(SE); B = 0.02 ± 0.01(SE); P < 0.02); and a unit increase in unhealthy diet scores was associated with a decrease in HRQoL (-0.01 ± 0.00; P < 0.05). In rural students alone, a unit increase in unhealthy diet score was associated with a decrease in HRQoL (B = -0.01 ± 0.00; P = 0.002), and in urban students a unit increase in healthy diet score was associated with an increase in HRQoL (B = 0.02 ± 0.00; P < 0.001).

CONCLUSIONS: Cross-sectional associations between diet quality and HRQoL were observed. Dietary modification may offer a target to improve HRQoL and general well-being; and consequently the prevention and treatment of adolescent health problems. Such interventions should consider gender and locality.

Obesity impacts on general practice appointments

Objective: To quantify the impact of obesity on the number of visits to both primary and secondary care teams.

Research Methods and Procedures: The adult populations of 80 general practices throughout the United Kingdom were classified according to their BMI. We undertook a cross-sectional survey of computer-generated and handwritten records of 6150 obese people (BMI ≥ 30 kg/m2) and 1150 normal weight (BMI = 18.5 to 24.9 kg/m2) control subjects over an 18-month retrospective period.

Results: Obese patients made significantly more visits to the general practitioner (GP), practice nurse (PN), and hospital outpatient units than normal weight patients (all p < 0.001), and they were admitted to the hospital more often (p = 0.034). For both GP and PN visits, the relationship remained after adjusting for age, sex, social deprivation category, country, and number of comorbidities. Among obese patients, there was an increasing relationship between frequent GP visits (at least four appointments) and greater BMI, which remained significant after adjustment had been made for age, sex, deprivation, country, and number of comorbidities.

Discussion: The human resource burden to general practice is significantly higher in the obese population than in the normal weight population, even when adjusted for confounding factors. The increase in prevalence of obesity will continue to put pressure on GP and PN time unless appropriate action is taken.

Explaining the variation in the management of lifestyle risk factors in primary health care: a multilevel cross sectional study

Background

Despite evidence for the effectiveness of interventions to modify lifestyle behaviours in the primary health care (PHC) setting, assessment and intervention for these behaviours remains low in routine practice. Little is known about the relative importance of various determinants of practice.

This study aimed to examine the relative importance of provider characteristics and attitudes, patient characteristics and consultation factors in determining the rate of assessment and intervention for lifestyle risk factors in PHC.

Methods

A prospective audit of assessment and intervention for lifestyle risk factors was undertaken by PHC nurses and allied health providers (n = 57) for all patients seen (n = 732) over a two week period. Providers completed a survey to assess key attitudes related to addressing lifestyle issues. Multi-level logistic regression analysis of patient audit records was undertaken. Associations between variables from both data sources were examined, together with the variance explained by patient and consultation (level 1) and provider (level 2) factors.

Results

There was significant variance between providers in the assessment and intervention for lifestyle risk factors. The consultation type and reason for the visit were the most important in explaining the variation in assessment practices, however these factors along with patient and provider variables accounted for less than 20% of the variance. In contrast, multi-level models showed that provider factors were most important in explaining the variance in intervention practices, in particular, the location of the team in which providers worked (urban or rural) and provider perceptions of their effectiveness and accessibility of support services. After controlling for provider variables, patients' socio-economic status, the reason for the visit and providers' perceptions of the 'appropriateness' of addressing risk factors in the consultation were all significantly associated with providing optimal intervention. Together, measured patient consultation and provider variables accounted for most (80%) of the variation in intervention practices between providers.

Conclusion

The findings highlight the importance of provider factors such as beliefs and attitudes, team location and work context in understanding variations in the provision of lifestyle intervention in PHC. Further studies of this type are required to identify variables that improve the proportion of variance explained in assessment practices.

The Capm and Fama-French models in Brazil: a comparative study

This paper confronts the Capital Asset Pricing Model - CAPM - and the 3-Factor Fama-French - FF - model using both Brazilian and US stock market data for the same Sample period (1999-2007). The US data will serve only as a benchmark for comparative purposes. We use two competing econometric methods, the Generalized Method of Moments (GMM) by (Hansen, 1982) and the Iterative Nonlinear Seemingly Unrelated Regression Estimation (ITNLSUR) by Burmeister and McElroy (1988). Both methods nest other options based on the procedure by Fama-MacBeth (1973). The estimations show that the FF model fits the Brazilian data better than CAPM, however it is imprecise compared with the US analog. We argue that this is a consequence of an absence of clear-cut anomalies in Brazilian data, specially those related to firm size. The tests on the efficiency of the models - nullity of intercepts and fitting of the cross-sectional regressions - presented mixed conclusions. The tests on intercept failed to rejected the CAPM when Brazilian value-premium-wise portfolios were used, contrasting with US data, a very well documented conclusion. The ITNLSUR has estimated an economically reasonable and statistically significant market risk premium for Brazil around 6.5% per year without resorting to any particular data set aggregation. However, we could not find the same for the US data during identical period or even using a larger data set. Este estudo procura contribuir com a literatura empírica brasileira de modelos de apreçamento de ativos. Dois dos principais modelos de apreçamento são Infrontados, os modelos Capital Asset Pricing Model (CAPM)e de 3 fatores de Fama-French. São aplicadas ferramentas econométricas pouco exploradas na literatura nacional na estimação de equações de apreçamento: os métodos de GMM e ITNLSUR. Comparam-se as estimativas com as obtidas de dados americanos para o mesmo período e conclui-se que no Brasil o sucesso do modelo de Fama e French é limitado. Como subproduto da análise, (i) testa-se a presença das chamadas anomalias nos retornos, e (ii) calcula-se o prêmio de risco implícito nos retornos das ações. Os dados revelam a presença de um prêmio de valor, porém não de um prêmio de tamanho. Utilizando o método de ITNLSUR, o prêmio de risco de mercado é positivo e significativo, ao redor de 6,5% ao ano.

Essays in macroeconomy and dynamic term-structure models

This thesis is composed of three articles with the subjects of macroeconomics and - nance. Each article corresponds to a chapter and is done in paper format. In the rst article, which was done with Axel Simonsen, we model and estimate a small open economy for the Canadian economy in a two country General Equilibrium (DSGE) framework. We show that it is important to account for the correlation between Domestic and Foreign shocks and for the Incomplete Pass-Through. In the second chapter-paper, which was done with Hedibert Freitas Lopes, we estimate a Regime-switching Macro-Finance model for the term-structure of interest rates to study the US post-World War II (WWII) joint behavior of macro-variables and the yield-curve. We show that our model tracks well the US NBER cycles, the addition of changes of regime are important to explain the Expectation Theory of the term structure, and macro-variables have increasing importance in recessions to explain the variability of the yield curve. We also present a novel sequential Monte-Carlo algorithm to learn about the parameters and the latent states of the Economy. In the third chapter, I present a Gaussian A ne Term Structure Model (ATSM) with latent jumps in order to address two questions: (1) what are the implications of incorporating jumps in an ATSM for Asian option pricing, in the particular case of the Brazilian DI Index (IDI) option, and (2) how jumps and options a ect the bond risk-premia dynamics. I show that jump risk-premia is negative in a scenario of decreasing interest rates (my sample period) and is important to explain the level of yields, and that gaussian models without jumps and with constant intensity jumps are good to price Asian options.

Using irregularly spaced returns to estimate multi-factor models: application to Brazilian equity data

Multi-factor models constitute a useful tool to explain cross-sectional covariance in equities returns. We propose in this paper the use of irregularly spaced returns in the multi-factor model estimation and provide an empirical example with the 389 most liquid equities in the Brazilian Market. The market index shows itself significant to explain equity returns while the US$/Brazilian Real exchange rate and the Brazilian standard interest rate does not. This example shows the usefulness of the estimation method in further using the model to fill in missing values and to provide interval forecasts.

Optimal auction with a general distribution: virtual valuation without densities

We characterize the optimal auction in an independent private values framework for a completely general distribution of valuations. We do this introducing a new concept: the generalized virtual valuation. To show the wider applicability of this concept we present two examples showing how to extend the classical models of Mussa and Rosen and Baron and Myerson for arbitrary distributions

Essays on the general equilibrium effects of barriers to trade on economic growth, foreign trade and the location of economic activity in Brazil

This work presents a fully operational interstate CGE model implemented for the Brazilian economy that tries to quantify both the role of barriers to trade on economic growth and foreign trade performance and how the distribution of the economic activity may change as the country opens up to foreign trade. Among the distinctive features embedded in the model, modeling of external scale economies, port efficiency and land-maritime transport costs provides an innovative way of dealing explicitly with theoretical issues related to integrated regional systems. In order to illustrate the role played by the quality of infrastructure and geography on the country‟s foreign and interregional trade performance, a set of simulations is presented where barriers to trade are significantly reduced. The relative importance of trade policy, port efficiency and land-maritime transport costs for the country trade relations and regional growth is then detailed and quantified, considering both short run as well as long run scenarios. A final set of simulations shed some light on the effects of liberal trade policies on regional inequality, where the manufacturing sector in the state of São Paulo, taken as the core of industrial activity in the country, is subjected to different levels of external economies of scale. Short-run core-periphery effects are then traced out suggesting the prevalence of agglomeration forces over diversion forces could rather exacerbate regional inequality as import barriers are removed up to a certain level. Further removals can reverse this balance in favor of diversion forces, implying de-concentration of economic activity. In the long run, factor mobility allows a better characterization of the balance between agglomeration and diversion forces among regions. Regional dispersion effects are then clearly traced-out, suggesting horizontal liberal trade policies to benefit both the poorest regions in the country as well as the state of São Paulo. This long run dispersion pattern, on one hand seems to unravel the fragility of simple theoretical results from recent New Economic Geography models, once they get confronted with more complex spatially heterogeneous (real) systems. On the other hand, it seems to capture the literature‟s main insight: the possible role of horizontal liberal trade policies as diversion forces leading to a more homogeneous pattern of interregional economic growth.

Multiple structural change models:a simulation analysis

In a reccnt paper. Bai and Perron (1998) considcrccl theoretical issues relatec\ lo lhe limiting distriblltion of estimators and test. statist.ics in the linear model \\'ith multiplc struct ural changes. \Ve assess. via simulations, the adequacy of the \'arious I1Iethods suggested. These CO\'er the size and power of tests for structural changes. the cO\'erage rates of the confidence Íntervals for the break dates and the relat.Í\'e merits of methods to select the I1umber of breaks. The \'arious data generating processes considered alIo,,' for general conditions OIl the data and the errors including differellces across segmcll(s. Yarious practical recommendations are made.

Bailey's measure of the welfare costs of infiation as a general-equilibrium measure

Lucas (2000) has ShO\nl t hat Baile,\"'s formula for t hc \\'elfare costs of inflatioIl caIl bc rcgardpd as an approximation to t hc gcneral-equilibriuIll IllCaSllH'S \\"hich emerge from thc Sidrauski anrl the shopping-time models, In this paper \\'c shm\' that Baile~"s mcaSllrc can bc cxactly obtairlf'd in tllf' Siclrauski geIleral-equilibri1lIn framp\\'ork under the assUIllption of quasilinpar prefpreIlC'cs, The rpslllt. based on ",heter or not \\'Palt h pffpcts are incorporatccl into t hp analysis, is also helpful in darif\'ing \\'hy Lucas' Illeasurp clerin'd from the Siclrauski model turns 01lt to be aIl upper bOllIlcl to Bailp~"s, T,,'o eXaInplcs arp used to illustratc t he main C'ondusions,

Moral hazard and nonlinear pricing in a general equilibrium model

The paper analyzes a two period general equilibrium model with individual risk and moral hazard. Each household faces two individual states of nature in the second period. These states solely differ in the household's vector of initial endowments, which is strictly larger in the first state (good state) than in the second state (bad state). In the first period households choose a non-observable action. Higher leveis of action give higher probability of the good state of nature to occur, but lower leveIs of utility. Households have access to an insurance market that allows transfer of income across states of oature. I consider two models of financiaI markets, the price-taking behavior model and the nonlínear pricing modelo In the price-taking behavior model suppliers of insurance have a belief about each household's actíon and take asset prices as given. A variation of standard arguments shows the existence of a rational expectations equilibrium. For a generic set of economies every equilibrium is constraíned sub-optímal: there are commodity prices and a reallocation of financiaI assets satisfying the first period budget constraint such that, at each household's optimal choice given those prices and asset reallocation, markets clear and every household's welfare improves. In the nonlinear pricing model suppliers of insurance behave strategically offering nonlinear pricing contracts to the households. I provide sufficient conditions for the existence of equilibrium and investigate the optimality properties of the modeI. If there is a single commodity then every equilibrium is constrained optimaI. Ir there is more than one commodity, then for a generic set of economies every equilibrium is constrained sub-optimaI.