Cross-sectional study of 24-hour urinary electrolyte excretion and associated health outcomes in a convenience sample of Australian primary schoolchildren: the salt and other nutrients in children (SONIC) study protocol

BACKGROUND: Dietary sodium and potassium are involved in the pathogenesis of cardiovascular disease. Data exploring the cardiovascular outcomes associated with these electrolytes within Australian children is sparse. Furthermore, an objective measure of sodium and potassium intake within this group is lacking. OBJECTIVE: The primary aim of the Salt and Other Nutrient Intakes in Children ("SONIC") study was to measure sodium and potassium intakes in a sample of primary schoolchildren located in Victoria, Australia, using 24-hour urine collections. Secondary aims were to identify the dietary sources of sodium and potassium, examine the association between these electrolytes and cardiovascular risk factors, and assess children's taste preferences and saltiness perception of manufactured foods. METHODS: A cross-sectional study was conducted in a convenience sample of schoolchildren attending primary schools in Victoria, Australia. Participants completed one 24-hour urine collection, which was analyzed for sodium, potassium, and creatinine. Completeness of collections was assessed using collection time, total volume, and urinary creatinine. One 24-hour dietary recall was completed to assess dietary intake. Other data collected included blood pressure, body weight, height, waist and hip circumference. Children were also presented with high and low sodium variants of food products and asked to discriminate salt level and choose their preferred variant. Parents provided demographic information and information on use of discretionary salt. Descriptive statistics will be used to describe sodium and potassium intakes. Linear and logistic regression models with clustered robust standard errors will be used to assess the association between electrolyte intake and health outcomes (blood pressure and body mass index/BMI z-score and waist circumference) and to assess differences in taste preference and discrimination between high and low sodium foods, and correlations between preference, sodium intake, and covariates. RESULTS: A total of 780 children across 43 schools participated. The results from this study are expected at the end of 2015. CONCLUSIONS: This study will provide the first objective measure of sodium and potassium intake in Australian schoolchildren and improve our understanding of the relationship of these electrolytes to cardiovascular risk factors. Furthermore, this study will provide insight into child taste preferences and explore related factors. Given the cardiovascular implications of consuming too much sodium and too little potassium, monitoring of these nutrients during childhood is an important public health initiative.

Neighbourhood environment, sitting time and motorised transport in older adults: a cross-sectional study in Hong Kong

OBJECTIVES: Sitting time is a public health concern. This study examined associations of objectively measured neighbourhood environmental attributes with non-transport sitting time and motorised transport in 484 Hong Kong older adults. Neighbourhood attributes encouraging walking may help older adults replace some sitting time at home and on motorised transport with light-to-moderate-intensity activities such as strolling around the neighbourhood or walking to/from neighbourhood destinations. Thus, we hypothesised environmental attributes found to be related to walking would show associations with non-transport sitting time and motorised transport opposite to those seen for walking. DESIGN: Cross-sectional. SETTING: Hong Kong, an ultradense urban environment. PARTICIPANTS: 484 ethnic Chinese Hong Kong residents aged 65+ recruited from membership lists of four Hong Kong Elderly Health Centres representing catchment areas of low and high transport-related walkability stratified by socioeconomic status (response rate: 78%). PRIMARY AND SECONDARY OUTCOME MEASURES: Attributes of participants' neighbourhood environments were assessed by environmental audits, while non-transport sitting time and motorised transport were ascertained using the International Physical Activity Questionnaire-Long Form (Chinese version). RESULTS: Daily non-transport sitting minutes were 283 (SD=128) and motorised transport 23 (SD=28). Prevalence of signs of crime/disorder, streetlights, public facilities (toilets and benches) and pedestrian safety were independently negatively related, and sloping streets positively related, to sitting outcomes. Places of worship in the neighbourhood were predictive of more, and prevalence of public transit points of less, non-transport sitting. Associations of either or both sitting outcomes with prevalence of food/grocery stores and presence of parks were moderated by path obstructions and signs of crime/disorder. CONCLUSIONS: The findings suggest that access to specific destinations and relatively low-cost, minimal impact modifications to the urban form, such as street lighting, public toilets, benches and public transit points, could potentially reduce sitting time and associated negative health outcomes in Hong Kong older adults.

Marginal and Interaction Effects in Ordered Response Models

In discrete choice models the marginal effect of a variable of interest that is interacted with another variable differs from the marginal effect of a variable that is not interacted with any variable. The magnitude of the interaction effect is also not equal to the marginal effect of the interaction term. I present consistent estimators of both marginal and interaction effects in ordered response models. This procedure is general and can easily be extended to other discrete choice models.

Cross-sectional averages versus principal components

In spite of the increased use of factor-augmented regressions in recent years, little is known regarding the relative merits of the two main approaches to estimation and inference, namely, the cross-sectional average and principal component estimators. By providing a formal comparison of the approaches, the current paper fills this gap in the literature.

A simple test for cointegration in dependent panels with structural breaks

This paper develops a very simple test for the null hypothesis of no cointegration in panel data. The test is general enough to allow for heteroskedastic and serially correlated errors, unit-specific time trends, cross-sectional dependence and unknown structural breaks in both the intercept and slope of the cointegrated regression, which may be located at different dates for different units. The limiting distribution of the test is derived, and is found to be normal and free of nuisance parameters under the null. A small simulation study is also conducted to investigate the small-sample properties of the test. In our empirical application, we provide new evidence concerning the purchasing power parity hypothesis. © Blackwell Publishing Ltd and the Department of Economics, University of Oxford, 2008.

Is there really a unit root in the inflation rate? More evidence from panel data models

Time series unit root evidence suggests that inflation is nonstationary. By contrast, when using more powerful panel unit root tests, Culver and Papell (1997) find that inflation is stationary. In this article, we test the robustness of this result by applying a battery of recent panel unit root tests. The results suggest that the stationarity of inflation holds even after controlling for cross-sectional dependence and structural change.

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.