Design of cross-sectional surveys using cluster sampling: an overview with Australian case studies

Methodological issues of retrospective surveys for measuring mortality of highly clustered diseases: case study of the 2014-16 Ebola outbreak in Bo District, Sierra Leone

BACKGROUND

There is a lack of empirical data on design effects (DEFF) for mortality rate for highly clustered data such as with Ebola virus disease (EVD), along with a lack of documentation of methodological limitations and operational utility of mortality estimated from cluster-sampled studies when the DEFF is high.

OBJECTIVES

The objectives of this paper are to report EVD mortality rate and DEFF estimates, and discuss the methodological limitations of cluster surveys when data are highly clustered such as during an EVD outbreak.

METHODS

We analysed the outputs of two independent population-based surveys conducted at the end of the 2014-2016 EVD outbreak in Bo District, Sierra Leone, in urban and rural areas. In each area, 35 clusters of 14 households were selected with probability proportional to population size. We collected information on morbidity, mortality and changes in household composition during the recall period (May 2014 to April 2015). Rates were calculated for all-cause, all-age, under-5 and EVD-specific mortality, respectively, by areas and overall. Crude and adjusted mortality rates were estimated using Poisson regression, accounting for the surveys sample weights and the clustered design.

RESULTS

Overall 980 households and 6,522 individuals participated in both surveys. A total of 64 deaths were reported, of which 20 were attributed to EVD. The crude and EVD-specific mortality rates were 0.35/10,000 person-days (95%CI: 0.23-0.52) and 0.12/10,000 person-days (95%CI: 0.05-0.32), respectively. The DEFF for EVD mortality was 5.53, and for non-EVD mortality, it was 1.53. DEFF for EVD-specific mortality was 6.18 in the rural area and 0.58 in the urban area. DEFF for non-EVD-specific mortality was 1.87 in the rural area and 0.44 in the urban area.

CONCLUSION

Our findings demonstrate a high degree of clustering; this contributed to imprecise mortality estimates, which have limited utility when assessing the impact of disease. We provide DEFF estimates that can inform future cluster surveys and discuss design improvements to mitigate the limitations of surveys for highly clustered data.

Examining the extent, forms and factors influencing multiple job holding among medical doctors, professional nurses and rehabilitation therapists in two South African provinces: a cross-sectional study

OBJECTIVE

Multiple job holding (MJH), or working in more than one paid job simultaneously, is a common characteristic of health labour markets. The study examined the extent (prevalence), forms and factors influencing MJH among public sector medical doctors, professional nurses and rehabilitation therapists in two South African provinces.

DESIGN

A cross-sectional, analytical study.

SETTING

29 public sector hospitals in the Gauteng and Mpumalanga provinces of South Africa.

PARTICIPANTS

Full-time public sector medical doctors, professional nurses and rehabilitation therapists.

RESULTS

We obtained an overall response rate of 84.3%, with 486 medical doctors, 571 professional nurses and 340 rehabilitation therapists completing the survey. The mean age was 39.9±9.7 years for medical doctors, 43.7±10.4 years for professional nurses and 32.3±8.7 years for rehabilitation therapists. In the preceding 12 months, the prevalence of MJH was 33.7% (95% CI 25.8% to 42.6%) among medical doctors, 8.6% (95% CI 6.3% to 11.7%) among professional nurses and 38.7% (95% CI 31.5% to 46.5%) among rehabilitation therapists. Medical doctors worked a median of 20 (10-40) hours per month in their additional jobs, professional nurses worked 24 (12-34) hours per month and rehabilitation therapists worked 16 (8-28) hours per month. Private practice was the most prevalent form of MJH among medical doctors and rehabilitation therapists, compared with nursing agencies for professional nurses. MJH was significantly more likely among medical specialists (OR 4.3, p<0.001), married professional nurses (OR 2.4, p=0.022) and male rehabilitation therapists (OR 2.4, p=0.005).

CONCLUSION

The high prevalence of MJH could adversely affect the care of public sector patients. The study findings should inform the review and revision of existing MJH policies.

Malnutrition, Frailty, and Health-Related Quality of Life Among Rural Older Adults in Vietnam: A Cross-Sectional Study

Purpose

Rural older adults are more likely to be malnourished than urban older adults, particularly those living in lower-middle-income countries like Vietnam. Therefore, this study aimed to address the prevalence of malnutrition and its association with frailty and health-related quality of life in older rural Vietnamese adults.

Participants and Methods

This cross-sectional study was conducted on community-dwelling older adults (aged ≥ 60 years) living in a rural province in Vietnam. Nutritional status was determined using the Mini Nutritional Assessment Short Form (MNA-SF), and frailty was evaluated using the FRAIL scale. The 36-Item Short Form Survey (SF-36) was used to evaluate health-related quality of life.

Results

Among the 627 participants, 46 (7.3%) were malnourished (MNA-SF score <8), and 315 (50.2%) were at risk of malnutrition (MNA-SF score: 8-11). Individuals with malnutrition had significantly higher rates of impairments in instrumental activities of daily living and activities of daily living than those without malnutrition (47.8% vs 27.4% and 26.1% vs 8.7%, respectively). The prevalence of frailty was 13.5%. Risk of malnutrition and malnutrition were associated with high risks of frailty, with odds ratios of 2.14 (95% confidence interval [CI]: 1.16-3.93) and 4.78 (1.86-12.32), respectively. Furthermore, the MNA-SF score was positively correlated with eight domains of the health-related quality of life among rural older adults.

Conclusion

The prevalence rates of malnutrition, risk of malnutrition, and frailty were high among older adults in Vietnam. A strong association was observed between nutritional status and frailty. Therefore, this study reinforces the importance of screening for malnutrition and risk of malnutrition among older rural individuals. Further studies should explore whether early nutritional intervention reduces the risk of frailty among older adults and increase their health-related quality of life in the Vietnamese population.

Factors associated with knowledge about family planning and access to sexual and reproductive health services by sexually active immigrant youths in Hillbrow, South Africa: a cross-sectional study

Background

In South Africa, universal access to health care services, including those relating to sexual and reproductive health (SRH) care, is contained in Section 27 of the Constitution and commits the country to supporting the United Nations 2030 Agenda for the Sustainable Development Goals (SDGs). The objective of this study was to examine the factors associated with knowledge about family planning and access to SRH services among sexually active immigrant youths in Hillbrow, South Africa.

Method

This cross-sectional study was based on data from a household survey conducted in Hillbrow during December 2019. Interviewer-administered questionnaires were used to collect information from immigrant youths (18–34 years old). Data on 437 sexually active respondents was analysed in STATA 14 using univariate, bivariate, logistic, and multinomial regression models. A p-value of < 0.05 was chosen as the level of significance.

Results

About half of the respondents had poor knowledge about family planning; about one-third (35%) of the immigrant youths had no access to SRH services, 42% had some access, and 23% had access. The adjusted logistic regression model showed that being a female (AOR = 3.85, CI: 2.34–6.35, belonging to age group 30–34 years (AOR = 3.88, CI: 2.00–7.53); belonging to the rich wealth index (AOR = 2.55 (1.32–4.93); not having received information about family planning (AOR = 0.17, CI = 0.10–0.29) and not using a contraceptive at the time of the survey (AOR = 0.37, CI: 0.19–0.70) were factors associated with having knowledge about family planning. The adjusted multinomial regression shows that the factors associated with not having access to SRH services were secondary or higher level of education (ARRR = 1.89, 95% CI = 1.06–3.36), belonging to the rich wealth quintile (ARRR = 2.25, 95% CI = 1.00–5.07), being undocumented (ARRR = 0.49, 95% CI = 0.27–0.88), having experienced discrimination in Hillbrow (ARRR = 2.06, 95% CI = 1.15–3.67) and having received information about family planning 6 months prior to the survey (ARRR = 0.49, 95% CI = 0.26–0.90, p-value < 0.05).

Conclusion

To move towards realization of the Constitution of South Africa, achieve the SDGs, and curb associated negative SRH outcomes, there is a need to advocate for the implementation of universal access to SRH services that is inclusive of immigrant youths.

Access to SRH services by adolescents and youths has been a serious public health concern globally. In South Africa, universal access to health care including reproductive health care services is contained in Sect. 27 of the Constitution. The country is committed to the 2030 Agenda of the SDGs with the theme “leaving no one behind”. The objective of this study was to examine the factors associated with knowledge about family planning and access to SRH services among sexually active immigrant youths in Hillbrow, South Africa. Interviewer-administered questionnaires were used to collect information on the socio-demographic, migration, and reproductive health characteristics from 439 sexually active immigrant youths in Hillbrow during December 2019. The data were analysed to assess the factors associated with knowledge about family planning and access to SRH services. The findings show that 46% of the immigrant youth had poor knowledge about family planning, while 35% had no access to SRH services, 42% had some access and only 23% had access. The study showed that the factors associated with knowledge about family planning are female respondents, from the rich income group, those in the older age category, those who received information about family planning 6-months prior to the survey and those using a contraceptive at the time of the survey. The factors associated with having no access to SRH services were those respondents having completed secondary education and higher, from the rich income group, undocumented immigrants, those respondents having experienced discrimination in Hillbrow, youths not having received information about family planning prior to the survey, and those not using a contraceptive. It is important to make access to SRH services available to immigrant youths to prevent associated negative SRH outcomes among the youths.

Reasons of COVID-19 Vaccine Hesitancy among Chinese People Living with HIV/AIDS: A Structural Equation Modeling Analysis

Background

Many countries and organizations recommended people living with HIV/AIDS (PLWHA) receive the COVID-19 vaccine. However, vaccine hesitancy still exists and becomes a barrier for promoting COVID-19 vaccination among PLWHA.

Objective

This study aims to investigate factors that contributed to COVID-19 vaccine hesitancy among PLWHA.

Methods

The study used a multicenter cross-sectional design and an online survey mode. We recruited PLWHA aged 18-65 years from 5 metropolitan cities in China between January 2021 and February 2021. Participants completed an online survey through Golden Data, a widely used encrypted web-based survey platform. Multiple linear regression models were used to assess the background characteristics in relation to COVID-19 vaccine hesitancy, and structural equation modeling was performed to assess the relationships among perceived benefits, perceived risks, self-efficacy, subjective norms, and COVID-19 vaccine hesitancy.

Results

Among 1735 participants, 41.61% (722/1735) reported COVID-19 vaccine hesitancy. Older age, no other vaccinations in the past 3 years, and having chronic disease history were positively associated with COVID-19 vaccine hesitancy. Structural equation modeling revealed a direct relationship of perceived benefits, perceived risks, and subjective norms with self-efficacy and vaccine hesitancy and an indirect relationship of perceived benefits, perceived risks, and subjective norms with vaccine hesitancy. Moreover, self-efficacy toward COVID-19 vaccination was low. PLWHA had concerns of HIV disclosure during COVID-19 vaccination. Family member support could have an impact on COVID-19 vaccination decision-making.

Conclusions

COVID-19 vaccine hesitancy was high among PLWHA in China. To reduce COVID-19 vaccine hesitancy, programs and strategies should be adopted to eliminate the concerns for COVID-19 vaccination, disseminate accurate information on the safety and efficacy of the COVID-19 vaccine, encourage family member support for COVID-19 vaccination, and improve PLWHA’s trust of medical professionals.

Atrial fibrillation prevalence, awareness and management in a nationwide survey of adults in China

OBJECTIVE

To determine AF prevalence and gaps in atrial fibrillation (AF) awareness and management in China.

METHODS

We conducted a community-based survey of 47 841 adults (age ≥45 years) in seven geographic regions of China between 2014 and 2016. Participants underwent a structured questionnaire, a standard 12-lead ECG, physical examination and blood sampling. AF prevalence, defined by either ECG detection or self-report, was estimated according to sampling weights, non-response and age and sex distribution of the population. We used multivariable logistic regression to estimate associations among sociodemographic, clinical and geographic factors with the AF prevalence, awareness and treatment.

RESULTS

The weighted AF prevalence was 1.8% (95% CI 1.7% to 1.9%), but varied from 0.9% to 2.4% across geographical regions and equates to being present in an estimated 7.9 (95% CI 7.4 to 8.4) million people in China. Among men and women, the AF prevalence increased from 0.8% and 0.6% in the age group 45-54 years to 5.4% and 4.9% in the age group ≥75 years, respectively. Proportions of people who were aware of having AF decreased overall from 65.3% in 45-54 year-olds to 53.9% in ≥75 year-olds and varied between sex (men 58.5%, women 68.8%) and residency status (urban 78.3%, rural 35.3%). Only 6.0% of patients with high-risk AF received anticoagulation therapy.

CONCLUSIONS

AF prevalence is higher than previously reported in China, with low awareness and large treatment gaps. Large-scale efforts are urgently needed to reduce AF adverse consequences.

Workplace pedometer interventions for increasing physical activity

BACKGROUND

The World Health Organization (WHO) recommends undertaking 150 minutes of moderate-intensity physical activity per week, but most people do not. Workplaces present opportunities to influence behaviour and encourage physical activity, as well as other aspects of a healthy lifestyle. A pedometer is an inexpensive device that encourages physical activity by providing feedback on daily steps, although pedometers are now being largely replaced by more sophisticated devices such as accelerometers and Smartphone apps. For this reason, this is the final update of this review.

OBJECTIVES

To assess the effectiveness of pedometer interventions in the workplace for increasing physical activity and improving long-term health outcomes.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Occupational Safety and Health (OSH) UPDATE, Web of Science, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform from the earliest record to December 2016. We also consulted the reference lists of included studies and contacted study authors to identify additional records. We updated this search in May 2019, but these results have not yet been incorporated. One more study, previously identified as an ongoing study, was placed in 'Studies awaiting classification'.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of workplace interventions with a pedometer component for employed adults, compared to no or minimal interventions, or to alternative physical activity interventions. We excluded athletes and interventions using accelerometers. The primary outcome was physical activity. Studies were excluded if physical activity was not measured.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. When studies presented more than one physical activity measure, we used a pre-specified list of preferred measures to select one measure and up to three time points for analysis. When possible, follow-up measures were taken after completion of the intervention to identify lasting effects once the intervention had ceased. Given the diversity of measures found, we used ratios of means (RoMs) as standardised effect measures for physical activity.

MAIN RESULTS

We included 14 studies, recruiting a total of 4762 participants. These studies were conducted in various high-income countries and in diverse workplaces (from offices to physical workplaces). Participants included both healthy populations and those at risk of chronic disease (e.g. through inactivity or overweight), with a mean age of 41 years. All studies used multi-component health promotion interventions. Eleven studies used minimal intervention controls, and four used alternative physical activity interventions. Intervention duration ranged from one week to two years, and follow-up after completion of the intervention ranged from three to ten months. Most studies and outcomes were rated at overall unclear or high risk of bias, and only one study was rated at low risk of bias. The most frequent concerns were absence of blinding and high rates of attrition. When pedometer interventions are compared to minimal interventions at follow-up points at least one month after completion of the intervention, pedometers may have no effect on physical activity (6 studies; very low-certainty evidence; no meta-analysis due to very high heterogeneity), but the effect is very uncertain. Pedometers may have effects on sedentary behaviour and on quality of life (mental health component), but these effects were very uncertain (1 study; very low-certainty evidence). Pedometer interventions may slightly reduce anthropometry (body mass index (BMI) -0.64, 95% confidence interval (CI) -1.45 to 0.18; 3 studies; low-certainty evidence). Pedometer interventions probably had little to no effect on blood pressure (systolic: -0.08 mmHg, 95% CI -3.26 to 3.11; 2 studies; moderate-certainty evidence) and may have reduced adverse effects (such as injuries; from 24 to 10 per 100 people in populations experiencing relatively frequent events; odds ratio (OR) 0.50, 95% CI 0.30 to 0.84; low-certainty evidence). No studies compared biochemical measures or disease risk scores at follow-up after completion of the intervention versus a minimal intervention. Comparison of pedometer interventions to alternative physical activity interventions at follow-up points at least one month after completion of the intervention revealed that pedometers may have an effect on physical activity, but the effect is very uncertain (1 study; very low-certainty evidence). Sedentary behaviour, anthropometry (BMI or waist circumference), blood pressure (systolic or diastolic), biochemistry (low-density lipoprotein (LDL) cholesterol, total cholesterol, or triglycerides), disease risk scores, quality of life (mental or physical health components), and adverse effects at follow-up after completion of the intervention were not compared to an alternative physical activity intervention. Some positive effects were observed immediately at completion of the intervention periods, but these effects were not consistent, and overall certainty of evidence was insufficient to assess the effectiveness of workplace pedometer interventions.

AUTHORS' CONCLUSIONS

Exercise interventions can have positive effects on employee physical activity and health, although current evidence is insufficient to suggest that a pedometer-based intervention would be more effective than other options. It is important to note that over the past decade, technological advancement in accelerometers as commercial products, often freely available in Smartphones, has in many ways rendered the use of pedometers outdated. Future studies aiming to test the impact of either pedometers or accelerometers would likely find any control arm highly contaminated. Decision-makers considering allocating resources to large-scale programmes of this kind should be cautious about the expected benefits of incorporating a pedometer and should note that these effects may not be sustained over the longer term. Future studies should be designed to identify the effective components of multi-component interventions, although pedometers may not be given the highest priority (especially considering the increased availability of accelerometers). Approaches to increase the sustainability of intervention effects and behaviours over a longer term should be considered, as should more consistent measures of physical activity and health outcomes.

Increase of breast-feeding in the past decade in Greece, but still low uptake: cross-sectional studies in 2007 and 2017

OBJECTIVE

To estimate breast-feeding prevalence in Greece in 2007 and 2017, compare breast-feeding indicators and maternity hospital practices between these years, and investigate breast-feeding determinants.

DESIGN

Two national cross-sectional studies (2007 and 2017) using systematic cluster sampling of babies with the same sampling design, data collection and analysis methodology.

SETTING

Telephone interview with babies' mothers or fathers.

PARTICIPANTS

Representative sample of infants who participated in the national neonatal screening programme (n 549 in 2017, n 586 in 2007).

RESULTS

We found that breast-feeding indicators were higher in 2017 compared with 10 years before. In 2017, 94 % of mothers initiated breast-feeding. Breast-feeding rates were 80, 56 and 45 % by the end of the 1st, 4th and 6th completed month of age, respectively. At the same ages, 40, 25 and <1 % of babies, respectively, were exclusively breast-feeding. We also found early introduction of solid foods (after the 4th month of age). Maternity hospital practices favouring breast-feeding were more prevalent in 2017, but still suboptimal (63 % experienced rooming-in; 51 % experienced skin-to-skin contact in the first hour after birth; 19 % received free sample of infant formula on discharge).

CONCLUSIONS

We observed an increasing trend in all breast-feeding indicators in the past decade in Greece, but breast-feeding rates - particularly rates of exclusive breast-feeding - remain low. Systematic public health initiatives targeted to health professionals and mothers are needed in order to change the prevailing baby feeding 'culture' and successfully implement the WHO recommendations for exclusive breast-feeding during the first 6 months of life.

Identifying residual transmission of lymphatic filariasis after mass drug administration: Comparing school-based versus community-based surveillance - American Samoa, 2016

INTRODUCTION

Under the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted seven rounds of mass drug administration (MDA) from 2000-2006. The World Health Organization recommends systematic post-MDA surveillance using Transmission Assessment Surveys (TAS) for epidemiological assessment of recent LF transmission. We compared the effectiveness of two survey designs for post-MDA surveillance: a school-based survey of children aged 6-7 years, and a community-based survey targeting people aged ≥8 years.

METHODS

In 2016, we conducted a systematic school-based TAS in all elementary schools (N = 29) and a cluster survey in 28 villages on the two main islands of American Samoa. We collected information on demographics and risk factors for infection using electronic questionnaires, and recorded geo-locations of schools and households. Blood samples were collected to test for circulating filarial antigen (CFA) using the Alere Filariasis Test Strip. For those who tested positive, we prepared slides for microscopic examination of microfilaria and provided treatment. Descriptive statistics were performed for questionnaire variables. Data were weighted and adjusted to account for sampling design and sex for both surveys, and for age in the community survey.

RESULTS

The school-based TAS (n = 1143) identified nine antigen-positive children and found an overall adjusted CFA prevalence of 0.7% (95% CI: 0.3-1.8). Of the nine positive children, we identified one microfilariaemic 7-year-old child. The community-based survey (n = 2507, 711 households) identified 102 antigen-positive people, and estimated an overall adjusted CFA prevalence of 6.2% (95% CI: 4.5-8.6). Adjusted village-level prevalence ranged from 0-47.1%. CFA prevalence increased with age and was higher in males. Of 86 antigen-positive community members from whom slides were prepared, 22 (25.6%) were microfilaraemic. School-based TAS had limited sensitivity (range 0-23.8%) and negative predictive value (range 25-83.3%) but had high specificity (range 83.3-100%) and positive predictive value (range 0-100%) for identifying villages with ongoing transmission.

CONCLUSIONS

American Samoa failed the school-based TAS in 2016, and the community-based survey identified higher than expected numbers of antigen-positive people. School-based TAS was logistically simpler and enabled sampling of a larger proportion of the target population, but the results did not provide a good indication of the overall CFA prevalence in older age groups and was not sensitive at identifying foci of ongoing transmission. The community-based survey, although operationally more challenging, identified antigen-positive individuals of all ages, and foci of high antigen prevalence. Both surveys confirmed recrudescence of LF transmission.

Dietary Patterns, Cardiorespiratory and Muscular Fitness in 9⁻11-Year-Old Children from Dunedin, New Zealand

Research shows that cardiorespiratory (CRF) and muscular fitness in childhood are associated with a healthier cardiovascular profile in adulthood. Identifying factors associated with measures of fitness in childhood could allow for strategies to optimize cardiovascular health throughout the lifecourse. The aim of this study was to examine the association between dietary patterns and both CRF and muscular fitness in 9⁻11-year-olds. In this study of 398 children, CRF and muscular fitness were assessed using a 20-m shuttle run test and digital hand dynamometer, respectively. Dietary patterns were derived using principal component analysis. Mixed effects linear regression models were used to assess associations between dietary patterns and CRF and muscular fitness. Most children had healthy CRF (99%, FITNESSGRAM) and mean ± SD muscular fitness was 15.2 ± 3.3 kg. Two dietary patterns were identified; &ldquo;Snacks&rdquo; and &ldquo;Fruit and Vegetables&rdquo;. There were no significant associations between either of the dietary patterns and CRF. Statistically significant but not clinically meaningful associations were seen between dietary patterns and muscular fitness. In an almost exclusively fit cohort, food choice is not meaningfully related to measures of fitness. Further research to investigate diet-fitness relationships in children with lower fitness levels can identify key populations for potential investments in health-promoting behaviors.

Bayesian inference under cluster sampling with probability proportional to size

Cluster sampling is common in survey practice, and the corresponding inference has been predominantly design based. We develop a Bayesian framework for cluster sampling and account for the design effect in the outcome modeling. We consider a two-stage cluster sampling design where the clusters are first selected with probability proportional to cluster size, and then units are randomly sampled inside selected clusters. Challenges arise when the sizes of the nonsampled cluster are unknown. We propose nonparametric and parametric Bayesian approaches for predicting the unknown cluster sizes, with this inference performed simultaneously with the model for survey outcome, with computation performed in the open-source Bayesian inference engine Stan. Simulation studies show that the integrated Bayesian approach outperforms classical methods with efficiency gains, especially under informative cluster sampling design with small number of selected clusters. We apply the method to the Fragile Families and Child Wellbeing study as an illustration of inference for complex health surveys.

Toxoplasma gondii infection in wild mustelids and cats across an urban-rural gradient

The increase in human population and domestic pets, such as cats, are generating important consequences in terms of habitat loss and pathogen pollution of coastal ecosystems with potential to generate negative impacts in marine biodiversity. Toxoplasma gondii is the etiological agent of zoonotic disease toxoplasmosis, and is associated with cat abundance and anthropogenic disturbance. The presence of T. gondii oocysts in the ocean has negatively affected the health status of the threatened Southern sea otter (Enhydra lutris nereis) populations. The present study analyzed seroprevalence and presence of T. gondii DNA in American mink (Neovison vison), Southern river otters (Lontra provocax) and domestic cats (Felis silvestris catus) in four different areas in Southern Chile comprising studies in rivers and lakes in Andean foothills and mountains, marine habitat and island coastal ecosystems. Mean seroprevalence of T. gondii in the study was 64% of 151 total animals sampled: 59% of 73 American mink, 77% of 13 Southern river otters, 68% of 65 domestic cats and in two of two kodkods (Leopardus guigna). Toxoplasma gondii DNA was detected in tissues from one American mink and one Southern river otter. The present study confirms the widespread distribution of T. gondii in Southern Chile, and shows a high exposure of semiaquatic mustelids and domestic cats to the parasite. Cats and anthropogenic disturbance have a role in the maintenance of T. gondii infection in ecosystems of southern Chile.

Prevalence and sociodemographic risk factors of chlamydia, gonorrhoea and syphilis: a national multicentre STI survey in New Caledonia, 2012

OBJECTIVES

To estimate prevalence and identify sociodemographic risk factors for Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Treponema pallidum infections in New Caledonia.

METHOD

A national cross-sectional survey was undertaken using a three-stage random sampling of general practice surgeries and public dispensaries. Participants were included through opportunistic screening and using a systematic step for selection. The study sample was weighted to the general population aged 18-49 years. Prevalence and risk factors were calculated by logistic regression.

RESULTS

CT was the most common sexually transmitted infection, with a prevalence of 9% (95% CI 6.6% to %11.4), followed by NG 3.5% (95% CI 1.9% to 5.1%), previous or latent syphilis 3% (95% CI 1.7% to 4.3%), NG and CT co-infection 2.1% (95% CI 0.8% to 3.3%) and active syphilis 0.4% (95% CI 0.0% to 0.9%). Being from a young age group (18-25 years), being single, having a low level of education and province of residence were all associated with higher prevalence of all three STIs. Being of Melanesian origin was associated with higher prevalence of both CT and NG. There was a significant interaction between ethnic group and province of residence for prevalence of CT. Female gender was associated with higher prevalence of CT.

CONCLUSIONS

The prevalence of CT was similar to estimates from other healthcare-based surveys from the Pacific, but higher for NG and lower for active syphilis infection. All sexually transmitted infections estimates were much higher than those found in population-based surveys from Europe and the USA. The sociodemographic risk factors identified in this study will help guide targeted prevention and control strategies in New Caledonia.

Mortality in Iraq associated with the 2003-2011 war and occupation: findings from a national cluster sample survey by the university collaborative Iraq Mortality Study

BACKGROUND

Previous estimates of mortality in Iraq attributable to the 2003 invasion have been heterogeneous and controversial, and none were produced after 2006. The purpose of this research was to estimate direct and indirect deaths attributable to the war in Iraq between 2003 and 2011.

METHODS AND FINDINGS

We conducted a survey of 2,000 randomly selected households throughout Iraq, using a two-stage cluster sampling method to ensure the sample of households was nationally representative. We asked every household head about births and deaths since 2001, and all household adults about mortality among their siblings. We used secondary data sources to correct for out-migration. From March 1, 2003, to June 30, 2011, the crude death rate in Iraq was 4.55 per 1,000 person-years (95% uncertainty interval 3.74-5.27), more than 0.5 times higher than the death rate during the 26-mo period preceding the war, resulting in approximately 405,000 (95% uncertainty interval 48,000-751,000) excess deaths attributable to the conflict. Among adults, the risk of death rose 0.7 times higher for women and 2.9 times higher for men between the pre-war period (January 1, 2001, to February 28, 2003) and the peak of the war (2005-2006). We estimate that more than 60% of excess deaths were directly attributable to violence, with the rest associated with the collapse of infrastructure and other indirect, but war-related, causes. We used secondary sources to estimate rates of death among emigrants. Those estimates suggest we missed at least 55,000 deaths that would have been reported by households had the households remained behind in Iraq, but which instead had migrated away. Only 24 households refused to participate in the study. An additional five households were not interviewed because of hostile or threatening behavior, for a 98.55% response rate. The reliance on outdated census data and the long recall period required of participants are limitations of our study.

CONCLUSIONS

Beyond expected rates, most mortality increases in Iraq can be attributed to direct violence, but about a third are attributable to indirect causes (such as from failures of health, sanitation, transportation, communication, and other systems). Approximately a half million deaths in Iraq could be attributable to the war. Please see later in the article for the Editors' Summary.

Reliability and validity of the Adolescent Stress Questionnaire in a sample of European adolescents--the HELENA study

Background

Since stress is hypothesized to play a role in the etiology of obesity during adolescence, research on associations between adolescent stress and obesity-related parameters and behaviours is essential. Due to lack of a well-established recent stress checklist for use in European adolescents, the study investigated the reliability and validity of the Adolescent Stress Questionnaire (ASQ) for assessing perceived stress in European adolescents.

Methods

The ASQ was translated into the languages of the participating cities (Ghent, Stockholm, Vienna, Zaragoza, Pecs and Athens) and was implemented within the HELENA cross-sectional study. A total of 1140 European adolescents provided a valid ASQ, comprising 10 component scales, used for internal reliability (Cronbach α) and construct validity (confirmatory factor analysis or CFA). Contributions of socio-demographic (gender, age, pubertal stage, socio-economic status) characteristics to the ASQ score variances were investigated. Two-hundred adolescents also provided valid saliva samples for cortisol analysis to compare with the ASQ scores (criterion validity). Test-retest reliability was investigated using two ASQ assessments from 37 adolescents.

Results

Cronbach α-values of the ASQ scales (0.57 to 0.88) demonstrated a moderate internal reliability of the ASQ, and intraclass correlation coefficients (0.45 to 0.84) established an insufficient test-retest reliability of the ASQ. The adolescents' gender (girls had higher stress scores than boys) and pubertal stage (those in a post-pubertal development had higher stress scores than others) significantly contributed to the variance in ASQ scores, while their age and socio-economic status did not. CFA results showed that the original scale construct fitted moderately with the data in our European adolescent population. Only in boys, four out of 10 ASQ scale scores were a significant positive predictor for baseline wake-up salivary cortisol, suggesting a rather poor criterion validity of the ASQ, especially in girls.

Conclusions

In our European adolescent sample, the ASQ had an acceptable internal reliability and construct validity and the adolescents' gender and pubertal stage systematically contributed to the ASQ variance, but its test-retest reliability and criterion validity were rather poor. Overall, the utility of the ASQ for assessing perceived stress in adolescents across Europe is uncertain and some aspects require further examination.

Estimating prevalence of common chronic morbidities in Australia

OBJECTIVES

To estimate prevalence of selected diagnosed chronic diseases among patients attending general practice, in the general practice patient population, and in the Australian population, and to compare population estimates with those of the National Health Survey (NHS).

DESIGN, SETTING AND PARTICIPANTS

In late 2005, 305 general practitioners each provided data for about 30 consecutive patients (total, 9156) as part of the BEACH (Bettering the Evaluation And Care of Health) program, a continuous national study of general practice activity. GPs used their knowledge of the patient, patient self-report, and medical records as sources.

MAIN OUTCOME MEASURES

Crude prevalence of each listed condition currently under management among surveyed patients, and adjusted prevalence for the general practice patient population, and the national population.

RESULTS

39.6% of respondents had none of the listed conditions diagnosed; 30.0% had a cardiovascular problem (uncomplicated hypertension, 17.6%; ischaemic heart disease, 9.5%); 24.8% had a psychological problem (depression, 14.2%; anxiety, 10.7%); 22.8% had arthritis, mostly osteoarthritis (20.0%); 10.7% had asthma; and 8.3% had diabetes, mostly type 2 (7.2%). Adjustment to the population attending general practice resulted in lower estimates for cardiovascular disease, arthritis and diabetes but had little effect on prevalence of asthma and psychological problems. After adjusting for non-attenders, about one in five people in the population had a cardiovascular problem, a similar proportion had a psychological problem, 14.8% had arthritis, and about 10% had asthma, hyperlipidaemia and gastro-oesophageal reflux disease. Estimates were similar to NHS results for any arthritis, asthma, and malignant neoplasms; higher for any cardiovascular problem; far higher for specific cardiovascular diseases, cerebrovascular disease and hyperlipidaemia; and almost twice the NHS estimate for psychological problems (particularly depression and anxiety). Estimates for type 1 diabetes aligned with NHS results, but were far higher for "all diabetes" and type 2 diabetes.

CONCLUSIONS

This study offers an alternative, perhaps more accurate, approach to measurement of disease prevalence than the NHS approach, which relies on respondent self-report alone. It provides valid prevalence estimates with the help of GPs at a fraction of the cost of the NHS. This study could be repeated annually to augment other data sources and better define existing health needs in the population.

Intraclass correlations among physiologic measures in children and adolescents

BACKGROUND

Cluster designs have become increasingly popular in many research areas. Adopting these designs requires special considerations because individuals within the same cluster may be correlated. Therefore, appropriate sample size calculations in these settings require the incorporation of additional information regarding intraclass or intracluster correlations (ICCs), which measure the degree of similarity between individuals within the same cluster or class.

OBJECTIVES

To discuss the importance of the ICC in cluster-designed studies and present ICC estimates for selected physiologic characteristics in children and adolescents.

METHOD

The ICCs for body mass index (BMI), sum of skinfolds (SSF), blood pressure, glucose, insulin, and lipids were determined using baseline data from the Cardiovascular Health in Children and Youth Studies (CHIC II and III). The ICC estimates presented were obtained through the use of mixed models for the entire data set and separately by age groups, gender, and ethnicity.

RESULTS

The estimated ICCs ranged from .0104 for BMI to .1657 for glucose. The differences in the estimated ICCs among the three age groups were most marked for blood pressure, SSF, and glucose and were small for aerobic power, insulin, and lipids. The greatest difference in ICC by gender was in BMI and SSF: The ICC for SSF in girls was 8.2 times larger than that for boys. Caucasians had higher ICC estimates for insulin than did African Americans and other ethnic groups.

DISCUSSION

The magnitude of the ICC varied by the outcome of interest, and factors such as age, gender, and ethnicity also influenced the magnitude of the ICC. The presence of ICCs should be assumed when using cluster designs, and ICCs should be considered when conducting sample size calculations for such studies.

Intraclass correlation coefficients from three cluster randomised controlled trials in primary and residential health care

OBJECTIVE

This paper provides intraclass correlation coefficients (ICCs) for estimation of sample size inflation required in future cluster randomised trials in primary or residential care.

METHODS

Three cluster randomised trials were conducted among middle-aged and older adults in primary care and residential care in Australia and New Zealand between 1995 and 2002. Baseline means or proportions, mean change, and ICCs with their standard errors and 95% confidence intervals are reported for outcome variables used in the three studies. The ICCs were estimated from a one-way random effects model using the analysis of variance method.

RESULTS

ICCs for quality of life and psychological variables in the primary care studies were low (below 0.018). ICCs for clinical and physical activity variables ranged from 0 to 0.08. ICCs for health and functional status in residential care for the elderly were high, ranging from 0.025 to 0.514.

CONCLUSIONS

The magnitude of the intraclass correlation varies with the venue of the trial, the outcome variables used, and the expected effect of the intervention. However, the intraclass correlations provided will be useful for more appropriate planning of residential and primary care-based trials in the future.

Exploring factors that influence child use of dental services and toothbrushing in New Zealand

OBJECTIVES

To explore factors contributing to dental service use and toothbrushing among Mäori, Pacific and New Zealand European or Other (NZEO) children in New Zealand.

METHODS

Data were obtained from the 2002 National Child Nutrition Survey. Models representing demographic, socio-economic status (SES), lifestyle, dietary, food security and oral health paradigms were tested using logistic regression.

RESULTS

Mäori and Pacific children were more likely to not attend for dental care (OR: 1.99 and 2.05 respectively) than NZEO children when age, sex and time lived in New Zealand were accounted for. The addition of household (OR: 1.93 and 2.05 respectively) or lifestyle (OR: 1.95 and 1.81 respectively) factors resulted in minimal OR changes for Mäori or Pacific child dental attendance, whereas addition of dietary (OR: 1.44 and 1.23 respectively) and food security (OR: 1.43 and 1.32 respectively) items reduced the ORs of Mäori and Pacific child dental attendance so they no longer differed significantly to NZEO children. Addition of dental factors increased the ORs of Mäori and Pacific children not utilizing dental services compared with NZEO children (OR: 2.30 and 2.13 respectively). Mäori and Pacific children were more likely to not brush teeth (OR: 3.86 and 1.49 respectively) than NZEO children when age, sex and time lived in New Zealand were accounted for. Addition of dietary factors resulted in a 36% OR reduction of Mäori children not brushing (OR: 2.57), while addition of household SES (OR: 1.06), lifestyle (OR: 1.14), dietary (OR: 0.71) or food security factors (OR: 1.19) reduced the ORs of Pacific children so they were no longer significantly different to NZEO children.

CONCLUSIONS

Mäori and Pacific children were more likely to have not received dental care (variance largely explained by dietary and food security factors) and Mäori children were more likely to not brush their teeth (variance largely explained by dietary items) than NZEO children.

Brief report: Disposable income, and spending on fast food, alcohol, cigarettes, and gambling by New Zealand secondary school students

We describe self-reported sources of income and expenditure, and the association between part-time employment and spending on fast food, alcohol, cigarettes, and gambling for a sample of 3434 New Zealand (NZ) secondary school students (mean age 15.0 years). Disposable income was usually received from parents and guardians, but nearly 40% of students also reported receiving money from part-time employment. The proportion of students employed increased as socioeconomic rating increased, and was associated with increased purchasing of fast food and alcohol, and increased spending on cigarettes and gambling. Spending by youth has obvious public health implications, particularly when it is concentrated on products that have a negative health impact.

Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN-DREAMS 1): study design and research methodology

PURPOSE

To describe the methodology of the Sankara Nethralaya-Diabetic Retinopathy Epidemiology and Molecular Genetic Study (SN-DREAMS 1), an ongoing population-based study to estimate the prevalence of diabetes and diabetic retinopathy in urban Chennai, Tamil Nadu, South India, and also to elucidate the clinical, anthropometric, biochemical and genetic risk factors associated with diabetic retinopathy.

METHODS

In this ongoing study, we anticipate recruiting a total of 5830 participants. Eligible patients, over the age of 40 years, are enumerated using the multistage random sampling method. Demographic data, socioeconomic status, physical activity, risk of sleep apnea, dietary habits, and anthropometric measurements are collected. A detailed medical and ocular history and a comprehensive eye examination, including stereo fundus photographs, are taken at the base hospital. Biochemical investigations (total serum cholesterol, high-density lipoproteins, serum triglycerides, hemoglobin, glycosylated hemoglobin HbA1c) and genetic studies of eligible subjects are conducted. A computerized database is created for the records.

CONCLUSION

The study is expected to result in an estimate of the prevalence of diabetes and diabetic retinopathy and a better understanding of biochemical and genetic risk factors associated with diabetic retinopathy in an urban South Indian population. Worldwide, the prevalence of diabetes mellitus, in particular type II diabetes, is rising at an alarming rate. The World Health Organization (WHO) and International Diabetes Federation (IDF) have predicted that the number of cases of adult-onset diabetes would more than double by 2030 from the present level of 171 million to 366 million-an increase of 214%.1 In developed countries, this increase in diabetic population would be around 42% and in developing countries, particularly in India, it is even higher; i.e. 150%.1 In India, the prevalence of diabetes mellitus in the urban population is around 12.1%, as reported by the national urban diabetes study2 conducted in six major cities. Studies have shown the prevalence of diabetes to be higher among the high-income groups (25.5%) as compared to low-income groups (12.6%).3,4,5 The assessment of socioeconomic status was based on income,6, 7 education,2, 7 occupation2 or caste6-which are not representative of the actual socioeconomic status. In the present study, however, the sample was stratified on socioeconomic scoring. This scoring was calculated on the basis of several parameters such as the residence being rented or owned, the number of rooms in the house, the highest educational status, the highest salary, the highest occupation, material possessions (cycle, TV, audio, car, etc.) and house/land value. To the best of our knowledge, this kind of comprehensive socioeconomic scoring has not been done before for prevalence studies on diabetic retinopathy in the general population.

Observed intra-cluster correlation coefficients in a cluster survey sample of patient encounters in general practice in Australia

Background

Cluster sample study designs are cost effective, however cluster samples violate the simple random sample assumption of independence of observations. Failure to account for the intra-cluster correlation of observations when sampling through clusters may lead to an under-powered study. Researchers therefore need estimates of intra-cluster correlation for a range of outcomes to calculate sample size. We report intra-cluster correlation coefficients observed within a large-scale cross-sectional study of general practice in Australia, where the general practitioner (GP) was the primary sampling unit and the patient encounter was the unit of inference.

Methods

Each year the Bettering the Evaluation and Care of Health (BEACH) study recruits a random sample of approximately 1,000 GPs across Australia. Each GP completes details of 100 consecutive patient encounters. Intra-cluster correlation coefficients were estimated for patient demographics, morbidity managed and treatments received. Intra-cluster correlation coefficients were estimated for descriptive outcomes and for associations between outcomes and predictors and were compared across two independent samples of GPs drawn three years apart.

Results

Between April 1999 and March 2000, a random sample of 1,047 Australian general practitioners recorded details of 104,700 patient encounters. Intra-cluster correlation coefficients for patient demographics ranged from 0.055 for patient sex to 0.451 for language spoken at home. Intra-cluster correlations for morbidity variables ranged from 0.005 for the management of eye problems to 0.059 for management of psychological problems. Intra-cluster correlation for the association between two variables was smaller than the descriptive intra-cluster correlation of each variable. When compared with the April 2002 to March 2003 sample (1,008 GPs) the estimated intra-cluster correlation coefficients were found to be consistent across samples.

Conclusions

The demonstrated precision and reliability of the estimated intra-cluster correlations indicate that these coefficients will be useful for calculating sample sizes in future general practice surveys that use the GP as the primary sampling unit.

Balancing the number and size of sites: an economic approach to the optimal design of cluster samples

The design of randomized controlled trials entails decisions that have economic as well as statistical implications. In particular, the choice of an individual or cluster randomization design may affect the cost of achieving the desired level of power, other things being equal. Furthermore, if cluster randomization is chosen, the researcher must decide how to balance the number of clusters, or "sites," and the size of each site. This article investigates these interrelated statistical and economic issues. Its principal purpose is to elucidate the statistical and economic trade-offs to assist researchers to employ randomized controlled trials that have desired economic, as well as statistical, properties.

Methods and design of the Chennai Glaucoma Study

PURPOSE

To describe the methodology of a population-based study to estimate the prevalence of glaucoma in a rural and urban South Indian population and to study the genetics of glaucoma in this population.

METHODS

A sample size of 4758 each for rural and urban populations in the Indian state of Tamil Nadu was calculated. Eligible subjects aged 40 years and above from the rural study area covering 32 contiguous villages and the urban area comprising five random clusters in Chennai city are enumerated. Demographic data are collected in the field. A detailed clinical examination, including glaucoma diagnostic procedures, is conducted at the examination centre. Pedigree ascertainment and genetic studies are performed for subjects with occludable angles or glaucoma. Data are recorded in a computerised database.

CONCLUSIONS

This study is expected to result in an estimation of the prevalence and a better understanding of the genetics of glaucoma in this region.

Measuring socio-economic position in dietary research: is choice of socio-economic indicator important?

OBJECTIVES

To examine the association between socio-economic position (SEP) and diet, by assessing the unadjusted and simultaneously adjusted (independent) contributions of education, occupation and household income to food purchasing behaviour.

DESIGN

The sample was randomly selected using a stratified two-stage cluster design, and the response rate was 66.4%. Data were collected by face-to-face interview. Food purchasing was examined on the basis of three composite indices that reflected a household's choice of grocery items (including meat and chicken), fruit and vegetables.

SETTING

Brisbane City, Australia, 2000.

PARTICIPANTS

: Non-institutionalised residents of private dwellings located in 50 small areas (Census Collectors Districts).

RESULTS

When shopping, respondents in lower socio-economic groups were less likely to purchase grocery foods that were high in fibre and low in fat, salt and sugar. Disadvantaged groups purchased fewer types of fresh fruits and vegetables, and less often, than their counterparts from more advantaged backgrounds. When the relationship between SEP and food purchasing was examined using each indicator separately, education and household income made an unadjusted contribution to purchasing behaviour for all three food indices; however, occupation was significantly related only with the purchase of grocery foods. When education and occupation were simultaneously adjusted for each other, the socio-economic patterning with food purchase remained largely unchanged, although the strength of the associations was attenuated. When household income was introduced into the analysis, the association between education, occupation and food purchasing behaviour was diminished or became non-significant; income, however, showed a strong, graded association with food choice.

CONCLUSIONS

The food purchasing behaviours of socio-economically disadvantaged groups were least in accord with dietary guideline recommendations, and hence are more consistent with greater risk for the development of diet-related disease. The use of separate indicators for education, occupation and household income each adds something unique to our understanding of how socio-economic position is related to diet: each indicator reflects a different underlying social process and hence they are not interchangeable, and do not serve as adequate proxies for one another.

Socioeconomic differences in food purchasing behaviour and suggested implications for diet-related health promotion

BACKGROUND

The relationship between socioeconomic position (SEP) and diet has been examined mainly on the basis of food and nutrient intake. As a complement to this work, we focused on the socioeconomic patterning of food purchasing, as many educational dietary messages emphasize behaviours such as food choice when shopping. Also, the type of food people buy influences the quality of their nutrient intake.

METHODS

A probability sample of households in Brisbane City, Australia (n = 1003, 66.4% response rate). Data were collected using face-to-face interviews. SEP was measured using education, occupation and household income. Food purchasing was examined on the basis of grocery items (including meat and chicken) and fruit and vegetables.

RESULTS

Significant associations were found between each socioeconomic indicator and food purchasing. Persons from socioeconomically disadvantaged backgrounds were less likely to purchase grocery foods that were comparatively high in fibre and low in fat, salt and sugar. The least educated, those employed in blue-collar (manual) occupations and residents of low income households purchased fewer types of fruit and vegetables, and less regularly, than their higher status counterparts.

CONCLUSIONS

Health promotion efforts aimed at narrowing socioeconomic differences in food purchasing need to be designed and implemented with an understanding of, and a sensitivity to, the barriers to nutritional improvement that difficult life circumstances can impose.

A serosurvey evaluation of the school-based measles 'catch-up' immunisation campaign in Victorian school-aged children

OBJECTIVE

To determine the proportion of Victorian primary school students protected against measles infection one year after the completion of the measles 'catch-up' immunisation campaign of 1998 and to compare this with the proportion of year 9 and 10 (aged 14-16 years) students.

DESIGN & SETTING

Three-stage random cluster survey in Victorian primary and secondary schools.

MAIN OUTCOME MEASURES

Proportion of primary and year 9 and 10 secondary school students protected against measles infection one year after the completion of the mass 'catch-up' immunisation campaign.

SECONDARY OUTCOMES

the proportion of both primary and year 9 and 10 secondary school students protected against both mumps and rubella.

RESULTS

Of 1,037 Victorian primary and 2,357 years 9 and 10 secondary school students invited to participate in this study, 403 (39%) and 752 (32%) respectively provided a blood specimen for serological testing for antibodies against measles, mumps and rubella. 94.8% (95% confidence interval, 91.5, 96.9) of primary school and 93.1% (90.9, 94.8) of year 9 and 10 students were protected against measles infection.

CONCLUSION

One year after the completion of the school-based measles 'catch-up' immunisation campaign the level of protection in Victorian primary school aged students is sufficient to prevent the continuing circulation of measles virus within this age group. The proportion of year 9 and 10 secondary school students protected against measles is also probably sufficient to prevent continuing circulation of wild type virus in Victoria, even though this age group was not specifically targeted by the 'catch-up' campaign.