Non- and Semi-parametric Bayesian Inference with Recurrent Events and Coherent Systems Data

This dissertation deals with non- and semi-parametric Bayesian inference of gap-time distribution with recurrent event data and simultaneous inference of component and system reliabilities of coherent systems data. Recurrent event data arise from a wide variety of studies/fields such as clinical trials, epidemiology, public health, biomedicine (e.g. repeated heart attack, repeated tumor occurrences of a cancer patient). In Chapter 2 we develop nonparametric Bayes and empirical Bayes estimators of the survivor function \bar{F} = 1 - F, of the gap-time distribution by assigning a Dirichlet process prior on F. We develop a closed form estimator of \bar{F} as well as a procedure to sample from the posterior measure and thus construct point-wise credible intervals. Semiparametric Bayesian inference of the gap-time survivor function with the effect of covariates of a correlated recurrent event in the presence of censoring is considered in Chapter 3. A frailty model is considered to allow the association between inter-occurrence gap-times. We assign a gamma process prior on the baseline cumulative hazard function &Lambda 0 \u3c\sub\u3e and parametric prior distributions on the finite dimensional parameters associated with covariates and frailties. We derive the conditional posterior distributions of the unknown parameters of interest from the joint posterior distribution and employ Gibbs sampling techniques to obtain samples from the joint posterior distribution. In Chapter 4 we focus on nonparametric Bayesian inference of reliability of coherent systems which are prevalent in many settings such as in mechanical, engineering, military, and financial systems. In our nonparametric Bayesian approach we assign independent partition-based Dirichlet (PBD) priors, on the component distribution functions. A simultaneous inference procedure of component and system reliabilities is developed. Bayesian paradigm provides a more general estimator in the sense that we can recover corresponding nonparametric estimators as a limiting case of our developed estimators both in recurrent event and reliability settings

Lifestyle risk factors and metabolic markers of cardiovascular diseases in Bangladeshi rural-to-urban male migrants compared with their non-migrant siblings : a sibling-pair comparative study

Background The increasing prevalence of cardiovascular diseases (CVDs) in developing countries like Bangladesh has been linked to progressive urbanisation. Comparisons of rural and urban populations often find a higher prevalence of CVD risk factors in the urban population, but rural-to-urban migrants might have different CVD risk profiles than either rural or urban residents. This study aimed to describe differences in CVD risk factors between migrants and non-migrants siblings and to determine whether acculturation factors were associated with CVD risk factors among migrants. Methods Using a sibling-pair comparative study, 164 male migrant who migrated from Pirganj rural areas to Dhaka City and their rural siblings (total N = 328) were assessed by interview, anthropometric measurement, blood pressure and blood samples. Comparisons were made using linear or logistic mixed effects models. Findings Physical inactivity, inadequate intake of fruit and vegetables and possible existence of a mental health disorder had 3.3 (1.73; 6.16), 4.3 (2.32; 7.92) and 2.9 (1.37; 6.27) times higher odds among migrants than their rural siblings, respectively. Migrants watched television on average 20 minutes (95% CI 6.17-35.08 min/day) more per day than the rural sibling group whereas PUFA intake, fruit and vegetable and fish intake of the migrants were -5.3 gm/day (-6.91; -3.70), -21.6 serving/week (-28.20; -15.09), -14.1 serving/week (-18.32; -9.87), respectively, lower than that of the rural siblings. No significant difference was observed for other variables. After adjusting, the risk of physical inactivity, inadequate fruit and vegetable intake, a mental health disorder and low HDL were significantly higher in migrants than in rural siblings and tended to be higher for each increasing tertile of urban life exposure. Conclusion The findings suggest that migration from rural-to-urban environment increases CVD risk which exacerbate with time spent in urban area due to acculturation. This study gives new insights into the increased CVD risk related with migration and urbanization in Bangladesh

Seasonal variations in physical activity domains among rural and urban Bangladeshis using a culturally relevant Past Year Physical Activity Questionnaire (PYPAQ)

While the effect of weather and seasons on physical activity (PA) is well documented for leisure-time physical activities in western countries, scant information is available for developing countries where lifestyle PA is the major source of energy expenditure (EE). In Bangladesh, the traditional calendar divides the year to six seasons that last two months each: summer, rainy, autumn, late autumn, winter, and spring. We developed the Past Year Physical Activity Questionnaire to record culturally relevant physical activities and to help assess the seasonal variation in total and domain-specific PA in Bangladesh. We have applied this tool to 162 men and women aged 18–60 years residing in Dhaka city and in the northern rural district of Thakurgaon. Repeated measures analysis of variance (RMANOVA) was used to test for evidence of variation in PA between place and seasons. The age- and gender-adjusted model revealed significantly lower levels of EE in urban residents compared to rural residents across all seasons and domains. We also found evidence of seasonal variations in moderate-to-vigorous physical activity (MVPA) MET-min/ weekamong rural participants only; for total PA (ranging from 3192 in autumn to 4124 in winter; p = 0.0001) and for two domains: the occupation domain (ranging from 935 in autumn to 1645 in winter; p = 0.0001) and the leisure time domain(ranging from 229 in late autumn to 272 in rainy season; p = 0.005). Seasonality in gardening was also noted (ranging from 2.46 in late autumn to 29.28 in rainy season; p = 0.0001). There were no seasonal differences of total and domain-specific MVPA in urban except household-related PA. Among rural participants, PA was higher in the summer, rainy, and winter seasons and lower in autumn and late autumn. The most common leisure-time physical activities were walking, bicycling, and swimming with higher participation in the rural area. Leisure-time physical activity needs to be promoted to urban residents all year long but more focused on autumn, late autumn, and spring in rural areas

Applying quality improvement methods to neglected conditions: Development of the South Asia Burn Registry (SABR)

Objective: South Asia has the highest mortality rate from burns in the world. Application of quality improvement methods to burn care can help identify health system gaps. Our overall aim is to introduce a sustainable hospital-based burn registry for resource-constrained settings to assess health outcomes of burn injury patients presenting to dedicated burn injury centers in South Asia.Results: The South Asia Burn Registry (SABR) is implemented through collaborative approach in selected burn centers in Bangladesh and Pakistan. Th registry collects data on burn injury events, the care provided, and the functional status of patients at discharge from burn centers. It covers the entire spectrum of care provision for burn injury patients from the actual event through their discharge from the healthcare system. SABR investigates locally relevant contextual factors associated with burn injury and health-system requirements for burn patients receiving emergency and inpatient care in resource-constrained settings. It also explores factors associated with burn injury and care provision. SABR will inform better prevention and management efforts in South Asia and help to address healthcare needs of burn injury patients

Validation of a food frequency questionnaire as a tool for assessing dietary intake in cardiovascular disease research and surveillance in Bangladesh

Background: Cardiovascular disease (CVD) has emerged as a major public health concern in Bangladesh. Diet is an established risk factor for CVD but a tool to assess dietary intake in Bangladesh is lacking. This study aimed to validate a food frequency questionnaire (FFQ) using the 24-h dietary recall method and corresponding nutritional biological markers among rural and urban populations of Bangladesh. Method: Participants of both genders aged 18-60 years were included in the analysis (total n = 146, rural n = 94 and urban n = 52). Two FFQs of 166 items were administered three-months apart, during which time three 24-h dietary recalls were also completed. Participants were asked to recall their frequency of consumption over the preceding 3 months. Urine and blood samples were collected for comparison between FFQ-estimates of nutrients and their corresponding biomarkers. Methods were compared using unadjusted, energy-adjusted, de-attenuated correlation coefficients, 95% limits of agreement (LOA) and quartile classification. Results: Fair to moderate agreement for ranking energy, macro and micronutrients into quartiles was observed (weighted k value ranged from 0.22 to 0.58; p < 0.001 for unadjusted data) except for vitamin D (weighted k - 0.05) and zinc (weighted k 0.09). Correlation coefficients of crude energy, macronutrients and common micronutrients including vitamin E, thiamine, riboflavin, niacin, pyridoxine, folate, iron, magnesium, phosphorus, potassium, and sodium were moderately good, ranging from 0.42 to 0.78; p < 0.001 but only fair for vitamin A, β carotene and calcium (0.31 to 0.38; p < 0.001) and poor for vitamin D and zinc (0.02 and 0.16; p = ns, respectively). Energy-adjusted correlations were generally lower except for fat and vitamin E, and in range of - 0.017 (for calcium) to 0.686 (for fat). De-attenuated correlations were higher than unadjusted and energy- adjusted, and significant for all nutrients except for vitamin D (0.017) to 0.801 (for carbohydrate). The Bland Altman tests demonstrated that most of the coefficients were positive which indicated that FFQ provided a greater overestimation at higher intakes. More than one in three participants appeared to overestimate their food consumption based on the ratio of energy intake to basal metabolic rate cut points suggested by Goldberg. Absolute intake of macronutrients was 1.5 times higher and for micronutrients it ranged from 1.07 (sodium) to 26 times (Zinc). FFQ estimates correlated well for sodium (0.32; p < 0.001), and vitamin D (0.20; p = 0.017) with their corresponding biomarkers and iron (0.25; p = 0.003) with serum ferritin for unadjusted data. Folate, iron (with haemoglobin) and total protein showed inverse association; and fat and potassium showed poor correlation with their corresponding biomarkers for unadjusted data. However, folate showed significant positive correlation (0.189; p = 0.025) with biomarker after energy adjustment. Conclusion: Although FFQ showed overestimation for absolute intake in comparison with 24-h recalls, the validation study demonstrated acceptable agreement for ranking dietary intakes from FFQ with 24-h recall methods and some biomarkers and therefore could be considered as a tool to measure dietary intake for research and CVD risk factors surveillance in Bangladesh. The instrument may not be appropriate for monitoring population adherence to recommended intakes because of the overestimation

Randomized controlled trial on drowning prevention for parents with children aged below five years in Bangladesh: a study protocol

Background: Drowning is the third leading cause of death for children aged 0–4 years in many Asian countries, and is a serious but neglected health problem in low and middle-income countries like Bangladesh. The aim of the study is to outline the study protocol of a trial to test the efficacy of a mobile coach based intervention for the prevention of childhood drowning. Method/design: A two-arm cluster randomized community trial will be conducted to test the efficacy of the mobile coach intervention for childhood drowning on parents with children below five years of age and compared to an assessment only control group. A total of 1680 parents in the villages with children aged below five years of age will participate. The village will be used as a randomized unit, randomly assigned to an intervention group (N = 840) receiving the mobile coach based intervention or an assessment only control group (N = 840). An individualized mobile coach intervention based on the demographic data and the individual will be developed, and SMSs, audio messages, videos and images about childhood drowning will be sent to the participants of the intervention group over a period of six months. The participants will receive per week one text message (SMS) and image and one video and audio text per month. The primary outcome measure will be increased knowledge and safety awareness, and behaviour practice about childhood drowning assessed at the six-month follow-up, and the secondary outcome measure will be the reduced incidence of childhood drowning in Bangladesh. The study assistants conducting the baseline and the follow-up assessments will be blinded regarding the group assignment. Discussion: This is the first study testing a fully mobile coach intervention for childhood drowning prevention in Bangladesh. It is hoped that the programme will offer an effective and inexpensive way to prevent childhood drowning among children aged below five years and also increase the awareness of parents concerning the risks to their children from drowning

708y]i9h-p/i-Evaluation of quality and safety aspect of chilled prawn (<i>Macrobrachium rosenbergii</i>) during storage at -20⁰C

1188-1194Quality and safety aspect of chilled prawn (Macrobrachium rosenbergii) and changes there of during storage at -200C for 12 weeks was studied in a series of laboratory experiments. Quality was evaluated by examining organoleptic characteristics and biochemical composition. Safety aspect was evaluated by the detection of heavy metal (Cd, Cu), quantitative bacteriological analysis. Sensory quality evaluation showed that prawn remained in acceptable condition until 8 weeks of storage at -200C. Protein content of chilled prawn was 33.11% and after 8 weeks of storage at -200C it decreased to 25.41%. Moisture content of chilled prawn was 61.8% which was increased to 70.52% at 8 weeks of storage. Lipid content of chilled prawn was 2.27% and after 8 weeks of storage at -200C lipid content was 1.52%. Ash content of chilled prawn was 2.13% which was decreased to 1.43% after 8 weeks of storage at -200C. Heavy metal Cd and Cu concentration was 0.017 µg/g and 0.051 µg/g respectively and was within the consumable limit of World Health Organisation. TVBN of chilled prawn was 20.90 mg/100g which was increased to 26.32 mg/100g after 8 weeks of storage at -200C. APC of chilled prawn was 4.32 x 105 cfu/g which changed to 6.73 x 103 cfu/g after 8 weeks of storage at -200C. The present study revealed that the ice chilled prawn remain in acceptable condition for 8 weeks of storage at -200C

Epidemiology of childhood blindness : A community-based study in Bangladesh

This study aimed to investigate the prevalence and causes of childhood blindness in a rural area of Bangladesh. We adopted a cross-sectional quantitative study design for this study, which was performed in three unions (sub-districts) located in Raiganj Upazila of the Sirajganj district in Bangladesh. Using a validated tool, a screening program was conducted at the household level. After initial screening, a team of ophthalmologists confirmed the diagnoses by clinical examinations. The prevalence of childhood blindness was observed to be 6.3 per 10,000 children, whereas the rate of uniocular blindness was 4.8 per 10,000 children. Congenital problems were the major causes of both uniocular and binocular blindness (uniocular blindness: 84% and binocular blindness: 92%). The whole globe was the site responsible for binocular blindness (28.0%, 95% confidence interval [CI]: 13.1, 47.7), whereas the cornea was responsible for uniocular blindness (57.8%, 95% CI: 35.3, 78.1). Childhood blindness is a public health problem in Bangladesh and is highly prevalent, regardless of sex. The major causes of childhood blindness are congenital

Barriers to the uptake of eye health services of the children in rural Bangladesh: A community-based cross-sectional survey.

Globally, ocular morbidity and disability among children are major public health concerns. This study was designed to explore the health-seeking behaviours of parents in Bangladesh whose children have ocular problems. A cross-sectional mixed method was followed for this study. The method was designed to measure the eye health care-seeking practices of caregivers/parents with children with ocular morbidity in three unions (the lowest administrative geographical area comprising 30,000-50,000 population) of the Raiganj Upazila under the Sirajganj District of Bangladesh. The study period was from January to April 2017. Face-to-face interviews using a semi-structured quantitative questionnaire with the caregivers and KI were conducted among the health service providers during the study period. This was the first community-based study conducted in Bangladesh to find out caregivers' health-seeking behaviour with identified ocular morbidity. Among 198 confirmed cases of childhood ocular problems, only 87 (43.9%) parents sought health care for their children's ocular morbidities. Better health-seeking behavior was found among the wealthier families. Proportions were 55.3% and 36% among wealthy and low-income families, respectively. Affluent families sought care from qualified service providers. Educated household heads chose qualified service providers for their children at a higher rate than illiterate household heads. Lack of knowledge, lack of awareness and financial constraints are significant barriers to seeking proper health care. More than half of the caregivers did not seek any eye care services for their children. Socio-demographic factors, and financial constraints play an essential role in the health-seeking behaviour of the parents