Daily changes and short-term exposure patterns in time series studies of air pollution and acute health effects

This thesis investigated the effects of daily changes in exposure (delta) and short-term exposure patterns on the relationship between air pollution and health in time series studies. Using data from London and Hong Kong, delta was defined as the difference in particulate matter (PM10) concentration between successive days. Short-term exposure pattern series were defined based on number of peaks in PM10 within rolling weekly blocks. The mathematical equivalence of identifiable models for delta with conventional distributed lag model was derived and alternative model specifications were proposed. Measurement error and missing data exhibited more impact on delta than the absolute metrics in simulation studies. Evidence of association for delta PM10 with mortality was found only in Hong Kong which attenuated towards the null with more rigorous adjustment for weather. The pattern analysis approach hypothesized, in addition to amount (dose) and duration of exposure, epidemiological studies ought to take patterns of exposure into account. However, convincing evidence was not found for the effect of short-term exposure patterns on mortality risk estimates both in London and Hong Kong. Refining the definition of exposure patterns and methodological improvements including analysing data from multiple cities are highly recommended in related studies in the future

Neonatal iron distribution and infection susceptibility in full term, preterm and low birthweight babies in urban Gambia: study protocol for an observational study.

Background: Neonatal infection is the third largest cause of death in children under five worldwide.  Nutritional immunity is the process by which the host innate immune system limits nutrient availability to invading organisms. Iron is an essential micronutrient for both microbial pathogens and their mammalian hosts. Changes in iron availability and distribution have significant effects on pathogen virulence and on the immune response to infection. Our previously published data shows that, during the first 24 hours of life, full-term neonates have reduced overall serum iron. Transferrin saturation decreases rapidly from 45% in cord blood to ~20% by six hours post-delivery. Methods: To study neonatal nutritional immunity and its role in neonatal susceptibility to infection, we will conduct an observational study on 300 full-term normal birth weight (FTB+NBW), 50 preterm normal birth weight (PTB+NBW), 50 preterm low birth weight (PTB+LBW) and 50 full-term low birth weight (FTB+LBW), vaginally-delivered neonates born at Kanifing General Hospital, The Gambia. We will characterize and quantify iron-related nutritional immunity during the early neonatal period and use ex vivo sentinel bacterial growth assays to assess how differences in serum iron affect bacterial growth. Blood samples will be collected from the umbilical cord (arterial and venous) and at serial time points from the neonates over the first week of life. Discussion: Currently, little is known about nutritional immunity in neonates. In this study, we will increase understanding of how nutritional immunity may protect neonates from infection during the first critical days of life by limiting the pathogenicity and virulence of neonatal sepsis causing organisms by reducing the availability of iron. Additionally, we will investigate the hypothesis that this protective mechanism may not be activated in preterm and low birth weight neonates, potentially putting these babies at an enhanced risk of neonatal infection. Trial registration: clinicaltrials.gov ( NCT03353051) 27/11/2017

Early postnatal hypoferremia in low birthweight and preterm babies: A prospective cohort study in hospital-delivered Gambian neonates.

BACKGROUND: Neonates, particularly those born preterm (PTB) and with low birthweight (LBW), are especially susceptible to bacterial and fungal infections that cause an estimated 225,000 deaths annually. Iron is a vital nutrient for the most common organisms causing septicaemia. Full-term babies elicit an immediate postnatal hypoferremia assumed to have evolved as an innate defence. We tested whether PTB and LBW babies are capable of the same response. METHODS: We conducted an observational study of 152 babies who were either PTB (born ≥32 to <37 weeks gestational age) and/or LBW (<2500 g) (PTB/LBW) and 278 term, normal-weight babies (FTB/NBW). Blood was sampled from the umbilical cord vein and artery, and matched venous blood samples were taken from all neonates between 6-24 h after delivery. We measured haematological, iron and inflammatory markers. FINDINGS: In both PTB/LBW and FTB/NBW babies, serum iron decreased 3-fold within 12 h of delivery compared to umbilical blood (7·5 ± 4·5 vs 23·3 ± 7·1 ng/ml, P < 0·001, n = 425). Transferrin saturation showed a similar decline with a consequent increase in unsaturated iron-binding capacity. C-reactive protein levels increased over 10-fold (P < 0·001) and hepcidin levels doubled (P < 0·001). There was no difference in any of these responses between PTB/LBW and FTB/NBW babies. INTERPRETATION: Premature or low birthweight babies are able to mount a very rapid hypoferremia that is indistinguishable from that in normal term babies. The data suggest that this is a hepcidin-mediated response triggered by acute inflammation at birth, and likely to have evolved as an innate immune response against bacterial and fungal septicaemia. TRIAL REGISTRATION: clinicaltrials.gov (NCT03353051). Registration date: November 27, 2017. FUNDING: Bill & Melinda Gates Foundation (OPP1152353)

Exposure to household air pollution from solid cookfuels and childhood stunting: a population-based, cross-sectional study of half a million children in low- and middle-income countries

BACKGROUND: Household air pollution from the incomplete combustion of solid cookfuels in low- and middle-income countries (LMICs) has been largely ignored as a potentially important correlate of stunting. Our objective was to examine the association between solid cookfuel use and stunting in children aged <5 y. METHODS: We used data from 59 LMICs' population-based cross-sectional demographic and health surveys; 557 098 children aged <5 y were included in our analytical sample. Multilevel logistic regression was used to examine the association between exposure to solid cookfuel use and childhood stunting, adjusting for child sex, age, maternal education and number of children living in the household. We explored the association across key subgroups. RESULTS: Solid cookfuel use was associated with child stunting (adjusted OR 1.58, 95% CI 1.55 to 1.61). Children living in households using solid cookfuels were more likely to be stunted if they lived in rural areas, the poorest households, had a mother who smoked tobacco or were from the Americas. CONCLUSIONS: Focused strategies to reduce solid cookfuel exposure might contribute to reductions in childhood stunting in LMICs. Trial evidence to assess the effect of reducing solid cookfuel exposure on childhood stunting is urgently needed

Mass Drug Administration With Dihydroartemisinin-piperaquine and Malaria Transmission Dynamics in The Gambia: A Prospective Cohort Study

Contains fulltext : 208019.pdf (publisher's version ) (Open Access

Risk factors of infant mortality in rural The Gambia: a retrospective cohort study

Objective: The main objective was to assess the risk factors for infant mortality among children living in the Health and Demographic Surveillance System (HDSS) in Farafenni, The Gambia. Our secondary objective was to assess these risks separately in the neonatal and postneonatal (>28 days) period. Design: Retrospective cohort study. Setting: HDSS in an urban centre and surrounding area in The Gambia. Patients: 7365 infants (47% female) born between 2014 and 2018, of which 126 (1.71%) died in the first year. Main outcome measures: Infant mortality. Results: Risk factors for mortality were death of any sibling (HR 2.78, 95% CI 1.54 to 5.00), having a twin (HR 1.96, 95% CI 1.01 to 3.80), being born in the harvest season (HR 1.55, 95% CI 1.07 to 2.24), living in a rural village (HR 4.34, 95% CI 2.03 to 9.29) and longer distance to the nearest village with a public health centre (HR 1.33, 95% CI 1.11 to 1.59). In addition, no breast feeding (HR 10.73, 95% CI 6.83 to 16.86) and no BCG vaccination in the first week of life (HR 3.47, 95% CI 1.07 to 11.24) were associated with infant mortality. Similar risk factors were found in the neonatal and postneonatal periods. Conclusion: Most risk factors associated with infant mortality (neonatal and postneonatal) are not easily modifiable at the individual level and would require programmatic approaches to target vulnerable infants and facilitate access to health services

Tolerance of Gambian Plasmodium falciparum to Dihydroartemisinin and Lumefantrine Detected by Ex Vivo Parasite Survival Rate Assay.

Monitoring of Plasmodium falciparum sensitivity to antimalarial drugs in Africa is vital for malaria elimination. However, the commonly used ex vivo/in vitro 50% inhibitory concentration (IC50) test gives inconsistent results for several antimalarials, while the alternative ring-stage survival assay (RSA) for artemisinin derivatives has not been widely adopted. Here, we applied an alternative two-color flow cytometry-based parasite survival rate assay (PSRA) to detect ex vivo antimalarial tolerance in P. falciparum isolates from The Gambia. The PSRA infers parasite viability by quantifying reinvasion of uninfected cells following 3 consecutive days of drug exposure (10-fold the IC50 of drug for field isolates). The drug survival rate is obtained for each isolate from the slope of the growth/death curve. We obtained parasite survival rates of 41 isolates for dihydroartemisinin (DHA) and lumefantrine (LUM) out of 51 infections tested by ring-stage survival assay (RSA) against DHA. We also determined the genotypes for known drug resistance genetic loci in the P. falciparum genes Pfdhfr, Pfdhps, Pfmdr, Pfcrt, and Pfk13 The PSRA results determined for 41 Gambian isolates showed faster killing and lower variance after treatment with DHA than after treatment with LUM, despite a strong correlation between the two drugs. Four and three isolates were tolerant to DHA and LUM, respectively, with continuous growth during drug exposure. Isolates with the PfMDR1-Y184F mutant variant showed increased LUM survival, though the results were not statistically significant. Sulfadoxine/pyrimethamine (SP) resistance markers were fixed, while all other antimalarial variants were prevalent in more than 50% of the population. The PSRA detected ex vivo antimalarial tolerance in Gambian P. falciparum This calls for its wider application and for increased vigilance against resistance to artemisinin combination therapies (ACTs) in this population

Addressing challenges in tuberculosis adherence via performance-based payments for integrated case management: protocol for a cluster randomized controlled trial in Georgia.

From Europe PMC via Jisc Publications RouterHistory: ppub 2019-08-01, epub 2019-08-28Publication status: PublishedFunder: Department of Interational Development; Grant(s): MR/P015018/1Funder: Medical Research Council; Grant(s): MR/P015018/1Funder: Welcome Trust; Grant(s): MR/P015018/1Funder: Economic and Social Research Council; Grant(s): MR/P015018/1BACKGROUND:Tuberculosis is one of the greatest global health concerns and disease management is challenging particularly in low- and middle-income countries. Despite improvements in addressing this epidemic in Georgia, tuberculosis remains a significant public health concern due to sub-optimal patient management. Low remuneration for specialists, limited private-sector interest in provision of infectious disease care and incomplete integration in primary care are at the core of this problem. METHODS:This protocol sets out the methods of a two-arm cluster randomized control trial which aims to generate evidence on the effectiveness of a performance-based financing and integrated care intervention on tuberculosis loss to follow-up and treatment adherence. The trial will be implemented in health facilities (clusters) under-performing in tuberculosis management. Eligible and consenting facilities will be randomly assigned to either intervention or control (standard care). Health providers within intervention sites will form a case management team and be trained in the delivery of integrated tuberculosis care; performance-related payments based on monthly records of patients adhering to treatment and quality of care assessments will be disbursed to health providers in these facilities. The primary outcomes include loss to follow-up among adult pulmonary drug-sensitive and drug-resistant tuberculosis patients. Secondary outcomes are adherence to treatment among drug-sensitive and drug-resistant tuberculosis patients and treatment success among drug-sensitive tuberculosis patients. Data on socio-demographic characteristics, tuberculosis diagnosis and treatment regimen will also be collected. The required sample size to detect a 6% reduction in loss to follow-up among drug-sensitive tuberculosis patients and a 20% reduction in loss to follow-up among drug-resistant tuberculosis patients is 948 and 136 patients, respectively. DISCUSSION:The trial contributes to a limited body of rigorous evidence and literature on the effectiveness of supply-side performance-based financing interventions on tuberculosis patient outcomes. Realist and health economic evaluations will be conducted in parallel with the trial, and associated composite findings will serve as a resource for the Georgian and wider regional Ministries of Health in relation to future tuberculosis and wider health policies. The trial and complementing evaluations are part of Results4TB, a multidisciplinary collaboration engaging researchers and Georgian policy and practice stakeholders in the design and evaluation of a context-sensitive tuberculosis management intervention. TRIAL REGISTRATION:ISRCTN, ISRCTN14667607 . Registered on 14 January 2019