Human dietary exposure to chemicals in sub-Saharan Africa: safety assessment through a total diet study.

BACKGROUND: Human dietary exposure to chemicals can result in a wide range of adverse health effects. Some substances might cause non-communicable diseases, including cancer and coronary heart diseases, and could be nephrotoxic. Food is the main human exposure route for many chemicals. We aimed to assess human dietary exposure to a wide range of food chemicals. METHODS: We did a total diet study in Benin, Cameroon, Mali, and Nigeria. We assessed 4020 representative samples of foods, prepared as consumed, which covered more than 90% of the diet of 7291 households from eight study centres. By combining representative dietary surveys of countries with findings for concentrations of 872 chemicals in foods, we characterised human dietary exposure. FINDINGS: Exposure to lead could result in increases in adult blood pressure up to 2·0 mm Hg, whereas children might lose 8·8-13·3 IQ points (95th percentile in Kano, Nigeria). Morbidity factors caused by coexposure to aflatoxin B1 and hepatitis B virus, and sterigmatocystin and fumonisins, suggest several thousands of additional liver cancer cases per year, and a substantial contribution to the burden of chronic malnutrition in childhood. Exposure to 13 polycyclic aromatic hydrocarbons from consumption of smoked fish and edible oils exceeded levels associated with possible carcinogenicity and genotoxicity health concerns in all study centres. Exposure to aluminium, ochratoxin A, and citrinin indicated a public health concern about nephropathies. From 470 pesticides tested across the four countries, only high concentrations of chlorpyrifos in smoked fish (unauthorised practice identified in Mali) could pose a human health risk. INTERPRETATION: Risks characterised by this total diet study underscore specific priorities in terms of food safety management in sub-Saharan Africa. Similar investigations specifically targeting children are crucially needed. FUNDING: Standards and Trade Development Facility.

Modeling the spatial variability in the spread and correlation of childhood malnutrition in Nigeria.

The average nutritional status of children in Nigeria is, just as in most developing countries, still in an alarmingly bad condition. Prior studies have shown that this status relies on a series of different influences and can be measured by three anthropometric variables for stunting, wasting, and underweight. Different regression modeling techniques have been adopted over the years to explain the determinants and spatial clustering. Those indicators, however, show patterns that are not necessarily full filling requirements for ordinary regression models for the mean and are correlated among each other, a fact that has until now been ignored by most studies. Methods to model outcomes in the light of both, the whole distribution of and the correlation between two or more outcomes based on a set of covariates, have lately been developed. The aim of this paper is to make use of those methods to explain the underlying spatial structure in malnutrition in Nigeria. The study brings to limelight the pattern of spread as well as the interwoven relationships among childhood malnutrition indicators that would have otherwise remained unknown in Nigeria.

Methodology design of the regional Sub-Saharan Africa Total Diet Study in Benin, Cameroon, Mali and Nigeria.

The core food model was described more than three decades ago, and has been used ever since to identify main food contributors to dietary intakes for both nutrients and other food chemicals. The Sub-Saharan Africa Total Diet Study (SSA-TDS) uses this model to describe the food consumption habits of some selected populations of Benin, Cameroon, Mali, and Nigeria, prior to use in the completion of quantitative risk assessments with regard to food chemicals. Food consumption data were derived from food expenditure data contained in national household budget surveys that were provided by the national institutes of statistics in each country. A classification of African foods was established for the purpose of the study and core foods were selected, so as to reflect 96 ± 1% of the average national total diet expressed in weight. Populations from eight study centers were selected by national stakeholders. This approach involves the purchase of 4020 individual foods, prepared as consumed and pooled into 335 food composite samples, for analysis of mycotoxins, PAHs, PCBs and dioxins, pesticides, metals and trace elements, PFAs, and BFRs. This sampling plan aims to provide a representative, cost effective, and replicable approach for deterministic dietary exposure assessments in developing countries.

Joint modeling of Anaemia and Malaria in children under five in Nigeria.

Malaria and anaemia which jointly account for high proportion of morbidity and mortality among young children in developing countries have been individually studied using binary regression model. We adopt geoadditive latent variable model for binary/ordinal indicators to analyze the influence of variables of different types on the morbidity among young children in Nigeria. Latent variable models allow for the analysis of multidimensional response variables that reveal the indicator's underlying relationship that are caused by the latent variables. We extend the structural model to a semi-parametric geoadditive model in order to quantify the joint spatial structure of morbidity from malaria and anaemia. Findings revealed substantial geographical variations and the generated maps can guide policy makers and donors on how to prudently utilize the scarce resources for designing more cost-effective interventions.

Determinants of use of insecticide-treated nets among pregnant women in Nigeria.

BACKGROUND: Malaria in pregnancy is still a major health issue in Nigeria, accounting for about 33% of cause of maternal death. Despite massive efforts to make insecticide-treated net (ITN) available to pregnant women in Nigeria, the use is still low. This study was conducted to identify facilitators and inhibitors for the use of ITN/long-lasting insecticidal net (LLIN) among pregnant women in Nigeria. METHODS: Data were obtained from the 2011 State-Specific HIV & AIDS, Reproductive and Child Health Survey conducted in 18 states of Nigeria. The survey was a population-based study among men and women of reproductive age living in households in rural and urban areas of Nigeria. Multistage cluster sampling technique was used to select eligible respondents. The sample size per state was 960 respondents. Data were collected between October and November 2011. The analysis was done using Statistical Package for Social Sciences (SPSS) version 20. RESULTS: A total of 11.5% of the respondents were pregnant at the time of the survey of which 73.2% lived in rural location and approximately 70% were either not educated or attained at most a primary school education. A total of 93.2% of respondents have heard of net, 82.6% were confident that they can hang or use a net, and 64.6% owned an ITN/LLIN in their household while the actual use was just 19.2%. We found education, location (urban-rural), confidence to use a net, and knowledge that the use of a net can protect a pregnant woman from malaria to be significant at 5% level. The number of nets owned per household, the length of time the net is owned, age, and marital status were not significant. Multiple logistics regression shows that pregnant women who are confident to hang or use a net were almost ten times more likely to use a net than those who do not know, while those who know that the use of an ITN/LLIN can protect a pregnant woman from malaria were almost two times more likely to use a net than those who do not know. CONCLUSION: In general, while owning a net facilitates its use, ownership does not necessarily translate to usage. Owning more than one ITN/LLIN per household was not significant in the use of an ITN/LLIN by pregnant women in this study, neither was the length of time the net was owned. This study shows that increasing the number of nets owned per household might not be a critical decider on whether the net will be used or not. We recommend massive education on the use of ITN. Skill building on use and increasing knowledge on the benefits of using nets may contribute to improving ITN use among pregnant women in Nigeria.

A Bayesian multinomial modeling of spatial pattern of co-morbidity of malaria and non-malarial febrile illness among young children in Nigeria.

BACKGROUND: Children in developing countries continue to suffer mortality and morbidity from a number of illnesses, among which are malaria and non-malarial febrile illnesses, which epidemiologically overlap. We examined the spatial pattern and risk factors of co-morbidity of malaria and non-malarial febrile illness among children aged 6-59 months in Nigeria. METHOD: Using data from the 2010 Nigeria Malaria Indicator Survey, we considered the co-morbidity of malaria and non-malarial febrile illness among the children as multicategorical and selected a mixed multinomial logit model capable of incorporating covariates of different types. Inference was Bayesian, based on multicategorical linear mixed-model representation. RESULTS: We found that the risk of co-morbidity of malaria and non-malarial febrile illness increases as a child advances in age while the risk of non-malarial fever reduces after about 32 months of age. Area of residence (urban or rural), wealth index and type of roofing material used in the dwelling are other important risk factors for the co-morbidity found in this study. Further, children from four of Nigeria's 37 states are at high risk of malaria. CONCLUSIONS: Disease preventive measures need to be intensified, with more focus on rural areas and the poor. Campaigns for use of insecticide-treated bed nets need be more aggressive in all Nigerian states.

An assessment of the quality of advice provided by patent medicine vendors to users of oral contraceptive pills in urban Nigeria.

INTRODUCTION: In Nigeria about 50% of oral contraceptive pill users obtain their products from proprietary patent medicine vendors (PPMVs). This group of service providers are poorly trained and have very limited knowledge about contraception. This paper investigated the nature of the advice offered to simulated current and potential users of oral contraceptive pills. The main objective was to assess the nature and quality of advice provided by PPMVs to pill users. METHOD: This study is based on findings from a 'mystery client' approach in which three scenarios related to contraceptive pill use were simulated. Each of the 12 mystery clients simulated one of the following three scenarios: new pill users (new to family planning or switching from condom to pills); user seeking a resupply of pills; and dissatisfied pill users intending to discontinue use. Simple random sampling was used to select 410 PPMVs from a total of 1,826 in four states in Nigeria. Qualitative study using in-depth interviews was also conducted. RESULTS: A majority of the PPMVs had pills in stock on the day of the survey and resupplied pills to the clients. PPMVs also understood the reason and importance of referring clients who were new adopters of oral contraceptive methods to a health facility; 30% of the PPMVs referred new adopters to a health facility. However, demand from clients who do not want to go to health care facilities (for various reasons) necessitated the provision of oral contraceptive pills to 41% of the first time users. Some PPMVs prescribed treatment to mystery clients who presented with perceived complications arising from the use of pills, while 49% were referred to a health facility. CONCLUSION: The advice given by PPMVs often falls short of safety guidelines related to the use of oral contraceptive pills. There is a need to continuously update knowledge among the PPMVs to ensure that they provide quality oral contraceptive services as PPMVs bridge the gap between medical experts and users in rural communities.

Exclusive breastfeeding practice in Nigeria: a bayesian stepwise regression analysis.

Despite the importance of breast milk, the prevalence of exclusive breastfeeding (EBF) in Nigeria is far lower than what has been recommended for developing countries. Worse still, the practise has been on downward trend in the country recently. This study was aimed at investigating the determinants and geographical variations of EBF in Nigeria. Any intervention programme would require a good knowledge of factors that enhance the practise. A pooled data set from Nigeria Demographic and Health Survey conducted in 1999, 2003, and 2008 were analyzed using a Bayesian stepwise approach that involves simultaneous selection of variables and smoothing parameters. Further, the approach allows for geographical variations at a highly disaggregated level of states to be investigated. Within a Bayesian context, appropriate priors are assigned on all the parameters and functions. Findings reveal that education of women and their partners, place of delivery, mother's age at birth, and current age of child are associated with increasing prevalence of EBF. However, visits for antenatal care during pregnancy are not associated with EBF in Nigeria. Further, results reveal considerable geographical variations in the practise of EBF. The likelihood of exclusively breastfeeding children are significantly higher in Kwara, Kogi, Osun, and Oyo states but lower in Jigawa, Katsina, and Yobe. Intensive interventions that can lead to improved practise are required in all states in Nigeria. The importance of breastfeeding needs to be emphasized to women during antenatal visits as this can encourage and enhance the practise after delivery.

Possible determinants and spatial patterns of anaemia among young children in Nigeria: a Bayesian semi-parametric modelling.

BACKGROUND: Anaemia is a global public health problem affecting both developing and developed countries with major consequences for human health and socioeconomic development. This paper examines the possible relationship between Hb concentration and severity of anaemia with individual and household characteristics of children aged 6-59 months in Nigeria; and explores possible geographical variations of these outcome variables. METHODS: Data on Hb concentration and severity of anaemia in children aged 6-59 months that participated in the 2010 Nigeria Malaria Indicator Survey were analysed. A semi-parametric model using a hierarchical Bayesian approach was adopted to examine the putative relationship of covariates of different types and possible spatial variation. Gaussian, binary and ordinal outcome variables were considered in modelling. RESULTS: Spatial analyses reveal a distinct North-South divide in Hb concentration of the children analysed and that states in Northern Nigeria possess a higher risk of anaemia. Other important risk factors include the household wealth index, sex of the child, whether or not the child had fever or malaria in the 2 weeks preceding the survey, and children under 24 months of age. CONCLUSIONS: There is a need for state level implementation of specific programmes that target vulnerable children as this can help in reversing the existing patterns.

Determinants of condom use by men in extramarital relationships in Nigeria.

BACKGROUND: Extramarital sex is a high-risk behavior in terms of Human Immunodeficiency Virus (HIV) transmission, yet condom use in extramarital relationships is an understudied area in Africa, and Nigeria in particular, where such liaisons are not uncommon. This study highlights key determinants of condom use among men who engage in extramarital sex in Nigeria. METHODS: Results are based on a subsample of 642 married men from a combined dataset from three waves of the National HIV/AIDS and Reproductive Health Survey (NARHS), a set of multiround nationally representative surveys. Logistic regression was employed to explore possible determinants of condom use in extramarital sex. The motivation, opportunity, and ability model was applied in selecting the determinants. RESULTS: HIV risk-reduction knowledge was found not to be associated with condom use. At the full logistic regression model, being of the Yoruba tribe, having no misconception about HIV transmission, ability to discuss condom use, and ability to wear condoms were the key variables significantly associated with condom use in extramarital sex. CONCLUSION: Implementing HIV risk-reduction behavior change requires more than knowledge. Behavioral skills in condom use are critical. Intervention efforts should move away from knowledge about risk to concentrate on improving skills on how to discuss condom use and wear condoms correctly.

A profile on HIV prevalence and risk behaviors among injecting drug users in Nigeria: should we be alarmed?

OBJECTIVE: Injecting drug use is now recognized as a significant risk factor for HIV in sub-Saharan Africa. We evaluated prevalence and correlates of HIV among injecting drug users (IDUs) in Nigeria. METHODS: A cross sectional design using respondent driven sampling was conducted in six states in 2010. Weighted HIV prevalence and injecting risk behaviors calculated using RDS analytic tool. Logistic regression was used to determine correlates of HIV infection, stratified by state. RESULTS: Total numbers of IDUs ranged from 197 in Lagos to 273 in Cross River and Oyo states. HIV prevalence was highest in Federal Capital Territory (FCT) at 9.3%, Kaduna 5.8%, Oyo 5.1%, Kano 4.9%, CR 3.3% and Lagos 3.0%. Although >90% of participants were male, females had higher HIV prevalence in all states surveyed except FCT (range: 7.4% in CR to 37.7% in Kano). Logistic regression showed that females were significantly more likely to be HIV positive in Kano [OR=33.2, 95% CI: 6.8-160.4], Oyo [AOR=15.9, 95% CI: 3.69-68.51], Lagos [OR=15.5, 95% CI: 2.41-99.5] and Kaduna states [AOR=19.6, 95% CI: 4.4-87.6]. For injecting risk behavior, only receptive sharing was associated with HIV [AOR=7.6, 95% CI: 1.2-48.7] and [AOR=0.2, 95% CI: 0.04-0.92] in Oyo and Kaduna states respectively. CONCLUSIONS: Considerable heterogeneity in the prevalence of HIV and associated risk behaviors exist among IDUs across Nigeria. Females had higher HIV prevalence among IDUs in five of six states, suggesting a need for targeted interventions for this hidden subgroup. Further research is needed to understand HIV transmission dynamics of IDUs in Nigeria. Community-based opioid substitution therapy and needle exchange programs should be implemented without delay.

Modelling geographical variations and determinants of use of modern family planning methods among women of reproductive age in Nigeria.

Summary Understanding the level, trend, geographical variations and determinants of use of modern family planning (FP) plays a major role in designing effective interventions leading to increased usage. This study assessed these characteristics of FP use in Nigeria using data from the 2003, 2005 and 2007 National HIV/AIDS and Reproductive Health Survey, a national population-based household survey. A Bayesian geo-additive procedure was used, which provides flexible modelling of non-linear and spatial effects at a highly disaggregated level of states. The findings reveal considerable geographical variation in the use of modern FP in Nigeria, with a distinct north-south divide. Furthermore, a significant trend in the use of modern FP was evident, with an increase between 2003 and 2005 followed by a decline between 2005 and 2007. The effect of respondent's age was non-linear, and use of modern FP was found to differ significantly between never-married and currently/formerly married respondents. Awareness of FP methods and knowledge of where to get/buy FP services/methods were found to be significantly associated with usage. The findings provide policymakers with tools to prioritize the use of scarce resources for implementing FP and reproductive health interventions.

Determinants of insecticide-treated net ownership and utilization among pregnant women in Nigeria.

BACKGROUND: Malaria during pregnancy is a major public health problem in Nigeria leading to increase in the risk of maternal mortality, low birth weight and infant mortality. This paper is aimed at highlighting key predictors of the ownership of insecticide treated nets (ITNs) and its use among pregnant women in Nigeria. METHODS: A total of 2348 pregnant women were selected by a multi-stage probability sampling technique. Structured interview schedule was used to elicit information on socio-demographic characteristics, ITN ownership, use, knowledge, behaviour and practices. Logistic regression was used to detect predictors of two indicators: ITN ownership, and ITN use in pregnancy among those who owned ITNs. RESULTS: ITN ownership was low; only 28.8% owned ITNs. Key predictors of ITN ownership included women who knew that ITNs prevent malaria (OR = 3.85; p < 0001); and registration at antenatal clinics (OR = 1.34; p = 0.003). The use of ITNs was equally low with only 7.5% of all pregnant women, and 25.7% of all pregnant women who owned ITNs sleeping under a net. The predictors of ITN use in pregnancy among women who owned ITNs (N = 677) identified by logistic regression were: urban residence (OR = 1.87; p = 0.001); knowledge that ITNs prevent malaria (OR = 2.93; p < 0001) and not holding misconceptions about malaria prevention (OR = 1.56; p = 0.036). Educational level was not significantly related to any of the two outcome variables. Although registration at ANC is significantly associated with ownership of a bednet (perhaps through free ITN distribution) this does not translate to significant use of ITNs. CONCLUSIONS: ITN use lagged well behind ITN ownership. This seems to suggest that the current mass distribution of ITNs at antenatal facilities and community levels may not necessarily lead to use unless it is accompanied by behaviour change interventions that address the community level perceptions, misconceptions and positively position ITN as an effective prevention device to prevent malaria.

Relationship between care-givers' misconceptions and non-use of ITNs by under-five Nigerian children.

BACKGROUND: Malaria has been a major public health problem in Nigeria and many other sub-Saharan African countries. Insecticide-treated nets have shown to be cost-effective in the prevention of malaria, but the number of people that actually use these nets has remained generally low. Studies that explore the determinants of use of ITN are desirable. METHODS: Structured questionnaires based on thematic areas were administered by trained interviewers to 7,223 care-givers of under-five children selected from all the six geo-political zones of Nigeria. Bivariate analysis and multinomial logit model were used to identify possible determinants of use of ITN. RESULTS: Bivariate analysis showed that under-five children whose care-givers had some misconceptions about causes and prevention of malaria were significantly less likely to use ITN even though the household may own a net (p < 0.0001). Education and correct knowledge about modes of prevention of malaria, knowing that malaria is dangerous and malaria can kill were also significantly associated with use of ITN (p < 0.0001). Knowledge of symptoms of malaria did not influence use of ITN. Association of non-use of ITN with misconceptions about prevention of malaria persisted with logistic regression (Odds ratio 0.847; 95% CI 0.747 to 0.960). CONCLUSIONS: Misconceptions about causes and prevention of malaria by caregivers adversely influence the use ITN by under-five children. Appropriate communication strategies should correct these misconceptions.

Geoadditive latent variable modeling of count data on multiple sexual partnering in Nigeria.

The 2005 National HIV/AIDS and Reproductive Health Survey (NARHS) in Nigeria provides evidence that multiple sexual partnering increases the risk of contracting HIV and other sexually transmitted diseases. Therefore, partner reduction is one of the prevention strategies to accomplish the Millenium Development Goal of halting and reversing the spread of HIV/AIDS. We consider the numbers of girlfriends, casual, and commercial partners of heterosexual men, reported in the NARHS study, as observed indicators of their latent attitude toward multiple partnering. To explore the influence of risk factors on this latent variable, we extend semiparametric methodology for latent variable models with continuous and categorical indicators to include count indicators. This allows us to simultaneously analyze linear and nonlinear effects of covariates, such as sociodemographic factors and knowledge about HIV/AIDS, on attitude toward multiple sexual partnering, which in turn influences the observable count indicators. The results provide insights for policy makers who are aiming to reduce the spread of HIV and AIDS among the Nigerian populace through partner reduction.

Modelling level, trend and geographical variations in stigma and discrimination against people living with HIV/AIDS in Nigeria.

People living with HIV and AIDS (PLHA) often face stigma and discrimination. Stigma is a powerful tool for social control and PLHA are to varying degrees stigmatised against. Consequences of stigma and discrimination against PLHA may result in low turn-out for HIV counselling and testing, identity crises, isolation, loneliness, low self-esteem and lack of interest in containing the disease. To achieve the millennium development goal on HIV reduction, efforts should be targeted at measuring impact of HIV preventive interventions. In this paper, effort was made to explore geographical variations in addition to level and trend of accepting attitude towards PLHA using 2003 - 2007 population-based household survey data. Inferences are based on Markov Chain Monte Carlo techniques, while model selection was based on Deviance Information Criteria. Findings revealed significant positive trend and spatial variations on level of accepting attitude towards PLHA. Level of exposure to HIV prevention interventions and perceptions about social support received on HIV are significantly associated with accepting attitude towards PLHA. Findings provide policy makers with tools to discern states where prevention efforts on HIV-related stigma and discrimination should be intensified. This in turn, can enhance an effective utilization of scarce resources that is paramount in developing countries.

Analysing child mortality in Nigeria with geoadditive discrete-time survival models.

Child mortality reflects a country's level of socio-economic development and quality of life. In developing countries, mortality rates are not only influenced by socio-economic, demographic and health variables but they also vary considerably across regions and districts. In this paper, we analysed child mortality in Nigeria with flexible geoadditive discrete-time survival models. This class of models allows us to measure small-area district-specific spatial effects simultaneously with possibly non-linear or time-varying effects of other factors. Inference is fully Bayesian and uses computationally efficient Markov chain Monte Carlo (MCMC) simulation techniques. The application is based on the 1999 Nigeria Demographic and Health Survey. Our method assesses effects at a high level of temporal and spatial resolution not available with traditional parametric models, and the results provide some evidence on how to reduce child mortality by improving socio-economic and public health conditions.

Analyzing infant mortality with geoadditive categorical regression models: a case study for Nigeria.

In this paper, we analyze infant mortality in Nigeria based on the data set from the 1999 Nigeria Demographic and Health Survey (NDHS). We investigate spatial patterns at a highly disaggregated level of Nigerian states and consider non-linear effects of mother's age at birth. Time to the occurrence of a child's death can intuitively be considered to be categorical in nature and the determinants of a child's death may differ in different age groups. Thus, it may be desirable to investigate separately the death of a child in the first month and in the remaining 11 months of the first year of life. To avoid selection bias, the data set used for this case study is based on information on children who were born 12 months preceding the survey. Inference is Bayesian and is based on Markov chain Monte Carlo (MCMC) techniques. We find that spatial variation and the determinants of death indeed differ considerably for the two age groups considered.