scholarly works

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Statistical modelling of HIV/AIDS epidemics; Nigeria’s most needful statistical support for meeting the MDGs in HIV/AIDS intervention initiatives.
(Nigerian Statistical Association, 2006) Akpa, O. M.; Oyejola, B. A.
Since the first cases of AIDS were identified in the United State of America nearly two decades ago, researchers have made significant progress in understanding the epidemiology of HIV/AIDS Pandemic worldwide, with special attention to Sub-Saharan Africa. However, no particular attempt has been made to Model either the transmission dynamics or the trajectory of HIV/AIDS infection in Nigeria. In this paper, we review various methods adopted by Mathematicians and statisticians to Model HIV/AIDS epidemics. Their peculiar applicability and limitations with reference to Nigeria are discussed. We also discuss why Statistical Modeling of HIV/AIDS Epidemics is one of the most needed Statistical support for meeting the Millennium Development Goals (MDGs), particularly in Nigeria.
Modeling HIV/AIDS epidemics in West Africa: Results for UNAIDS modeling approach from some selected countries
(Medwell Journals, 2007) Akpa, O. M.; AyeIola, B. A.
The Estimation and Projection Package (EPP) developed by UNAIDS reference group have been used with some notable success in some countries of the sub-Saharan (East and South) African Countries. In this present studies, we present results for five modeling methods applied to four countries in the West African Sub region. Using five modeling assumption with respect to 2 data situations and paying attention to the parameters determining the dynamics of HIV/AIDS epidemics, we employ Epp to model the prevalence of the epidemic in four West African countries. We used these estimates to further explain the underlying trend in the epidemic in each of the selected countries. For the unedited data, our results shows that in 2005 the default model yielded 17.69% (Urban: 4.72%, Rural: 28.82%) for Nigeria, 5.23% (Urban: 4.48%, Rural: 6.18%) for Ghana, 4.75% (Urban: 5.28%, Rural: 4.33%) for Cote d'Ivoire and 0.54% (Urban: 0.49%, Rural: 0.59%) for Senegal. The computed Log-Likelihood (LL) estimates for the default model are (Urban: 187.8809, Rural: 4, 948. 3913), (Urban: 181.5688, Rural: 664.9529), (Urban: 320.0272, Rural: 388.4773) and (Urban: 45.7742, Rural: 78.0798) for Nigerian, Ghana, Cote d'Ivoire and Senegal, respectively.
The place of statistics in research and national development
(Taylor & Francis, 2007) Okewole, D. M.; Akpa, O. M.
The place of efficient and accurate application of Statistical methodologies (via development relevant research) in national development cannot be over emphasized. The ability to analyze data either manually or with the use of software is just a peripheral aspect of Statistics in the presence of critical issues such as planning and designing of experiment and research works generally. Consequent on this, collaborating with Statisticians become inevitable if meaningful output that would in turn affect national development is expected from a given research work. In this study, we critically accessed the place of Statistics, Statistical methodologies as well as the relevance of the knowledge of Statistics in national development as it sterns from academic and non academic research work in the field of medicine, Engineering, Agriculture, Arts (Humanities), Sciences and Social Sciences. The result of our study shows that Statistics is actively used in all these fields except in the Humanities where a minute percentage of the researchers make use of Statistical tools. Also, the quest for clearer understanding of Statistical methodologies was evident among the respondents who claimed that this would enhance their contribution to national development through quality research output.
Statistical modelling Of HIV/AIDS epidemic in the North Central zone Of Nigeria
(Internet Scientific Publications, 2007) Akpa, O.; Oyeloja, B.
The objective of this work were to apply the UNAIDS Estimation and Projection Package (EPP) to HIV/AIDS epidemic in the north central zone of Nigeria, to propose a statistical model for the course of the epidemic in the zone and to generally investigate the level of trend inherent in the epidemic, over the years. We used HIV/AIDS surveillance data to model the situation for the rural and urban sentinel sites in the zones. Using the EPP as our point of reference, we proposed a statistical model (based on modifications made to the original back calculation methods) for the course of HIV/AIDS epidemic in the zone. Our result shows that the UNAIDS package is a great AID to HIV/AIDS modeling in Nigeria. The incidence rate was estimated to be 0.91 in 1997, 0.7% in 2000 and projected to be 0.63 in 2010. Also an estimated 378,870 people are expected to die due to the epidemic in the year 2010. The prevalence peaked later than the incidence which peaked around 1997, but this is expected to rise slowly after 2007. The mortality rate is relatively low among sites inside major towns (IMT) than those outside major town (OMT), but the situation is generally still on the rise.
Psychological variables as correlates of university maladjustment behaviour
(Ife Centre for Psychological Studies, 2008) Arogunade, O. T.; Akpa, O. M.
The goal of the study was to examine the influence of some psychosocial variables like personality factors (extroversion, agreeableness, neuroticism, conscientiousness and openness), gender (male and female) and age in predicting university maladjustment. The participants, (M-42 & F-92) were 134 students in the age range 16-30 years randomly selected from a private University in Nigeria. The Big Five Personality inventory (BFI) and University Maladjustment Scale (UMS) were used to collect data Multiple Regression Analysis, Analysis of Variance (ANOVA) and t-test statistics were used to analyze the data. The result showed that all the psychosocial variables jointly predicted 87% of the University maladjustment variance. The implications in terms of screening fresh intakes into universities and minimizing student unrest were discussed.
Empirical Power Comparism of Three Correlation Coefficients
(Medwell Journals, 2008) Matthew, O. M.; Oyejola, B. A.
A Comparison of Pearson's moment (r), Kendall's (t) and the Spearman's rank (r2) correlations was made to find out when they may be suitable for use, particularly when the assumptions that support their use are violated. Bi-variate Samples of size n = 5, 10, 15, 20, 25, 30, 40, 50 and 100 from the normal and exponential distributions with population correlation values of p = 0, 0.25, 0.5, 0.75 and 0.9 (chosen to represent positive correlation between 0 and 1) were used. The power function for a = 0.01 and 0.05 was calculated for the tests. For the normal distribution, the Pearson's moment correlation coefficient was discovered to be the more powerful. However, in the exponential distribution, the power of the Pearson's moment correlation coefficient was lower than those of the non-parametric correlation coefficients, except for small sample sizes i.e, n≤15.
Analysis of trends and projections of the emergence, impact and the epidemiology of HIV/AIDS in Nigeria
(Nigerian Statistical Association, 2010) Akpa, O. M.; Oyejola, B. A.
The first case of AIDS was reported in Nigeria-(Lagos) in 1986. Since then, both the incidence and the prevalence of the epidemic has grown steadily, particularly during the military regimes. In this study, We used the UNAIDS softwares: Estimation and Projection Package-(EPP) and AIDS Impact Mode/-(AIM), to present models, trends analysis and projections/or the incidence a/HIVIAIDS in the six geopolitical zones in Nigeria. 0111' results show that the peak incidence 0/HIVIAIDS epidemics in the zones was during the Military rule in Nigeria. We also projected that by year 2010, the incidence are expected to be stable.
Modeling the transmission dynamics of HIV/AIDS epidemics: an introduction and a review
(Open Learning, 2010) Akpa, O. M.; Oyejola, B. A.
Introduction: One of the greatest causes of morbidity and mortality in the Sub-Saharan Africa, particularly among young adults, is HIV/AIDS. Many mathematical models have been suggested for describing the epidemiology as well as the epidemiological consequences of the epidemic. A review of some these models would aid researchers in applying them to better understand and control the incidence and distribution of the disease in their countries. Methodology: This study reviews some of the models proposed by various authors for describing the epidemiology as well as the epidemiological consequences of the HIV/AIDS epidemic and how some of them could be modified to suit the situations in other countries. We also discuss the limitations and the place of such models in the fight against the HIV epidemic. Results: A clear explanation of the premises and assumptions on which the models were based was reached by reviewing the models across different scenarios. Conclusion: Mathematical models have been very useful in HIV research, particularly for empirical studies on people living with HIV/AIDS (PLWHA). These models make predictions that generate questions of social and ethical interest.
Mathematical modeling of the epidemiology and the transmission dynamics of HIV/AIDS infections in Nigeria
(College of Medicine, University of Ibadan, 2010) Akpa, O. M.; Oyeloja, B. A.
Many of the already proposed models for the transmission of HIV/AIDS do not fit the situations in Nigeria. This is in part due to the fact that many of the models pay more attention to either homogeneity of sexual contact or population of homosexuals. Although some notable models have also been studied by different authors in times and places for heterosexual transmission of HIV/AIDS epidemics, none of these models addressed the peculiar transmission dynamics in Nigeria. In this study, we grouped the population into susceptible, infected and AIDS men and women with sexual contact as the major route for HIV transmission. Assuming a strong sexual network between the groups and with the AIDS group unable to contribute to infection, we formulated mathematical models for the heterosexual transmission dynamics of HIV/AIDS in Nigeria. Our models incorporated parameters and variables that describe the nature and the strength of the transmission across the groups. We also presented model predictions on pattern of mixing between and Within the groups and how these in turn determine the global dynamics of the epidemics in Nigeria. Our simulation results show that, an increase in the transmission probability as well as in the number of sexual partnership poses more treat to the population than other parameters. The model predictions show that the epidemics tend to level up after year 2010. The number of sexual partners change per year and the probability of an effective contact are among the most critical variables in the HIV/AIDS epidemics in a community of heterosexual Nigerians. Our results agree with recent findings of similar models for some Sub-Saharan African countries. Also, results from the predictions based on the most recent National HIV Seroprevalence Surveillance Survey conducted in Nigeria agree with our findings.
HIV/AIDS and the long-distance truck drivers in south-west Nigeria: A cross-sectional survey on the knowledge, attitude, risk behaviour and beliefs of truckers
(Elsevier Ltd., 2010) Atilola, G. O.; Akpa, O. M.; Komolafe, I. O. O.
Objectives: According to the last HIV surveillance survey conducted in 2008, the overall National HIV prevalence in Nigeria stands at 4.6%. Recent studies and estimates by UNAIDS/WHO show higher prevalences in some selected states in Nigeria. The focus of this study is to determine the prevalence, risk behaviour, attitude and knowledge of HIV among long-distance heavy-truckers from a cross sectional survey conducted in the south-west Nigeria. Methods: Four major truck terminals (devoted to long-distance trips) in south western Nigeria were identified. A cross-sectional survey was conducted using a total sample size of 451 truckers who consented to be interviewed. A questionnaire (in English, Hausa and Yoruba languages) for data collection on the socio-demographic, risk behaviour, attitude and knowledge of HIV from the truckers was also designed. The multiple logistic regressions analysis was used to assess the association between some selected variables and factors. Results: Only 164 (36.4%) participants out of the study population of 451 were tested for HIV (due to limited test facilities and consent) and the prevalence of HIV antibodies among the truckers was found to be 2.4% (4/164) with all the infected individuals being within 21—30 years of age. 309 (68.1%) of the respondents admitted that they were at risk of contracting HIV while a total of 249 (55.3%) admitted that they had more than one sexual partners. In addition, while 392 (86.9%) said it was important for them to know their HIV status, 88 (19.5%) said that they would commit suicide should they test positive for HIV.
Rural-urban differential in maternal mortality estimate in Nigeria, sub-Saharan Africa
(Cenresin Publications, 2010) Adebowale, S. A.; Fagbamigbe, F. A.; Bamgboye, E. A.
In developing countries, the traditional sources of demographic statistics in which the estimates of demographic indices are based are either non-existence or incomplete. Data requirements on maternal deaths are always very large and costly. The indirect method (sisterhood method) for estimating maternal deaths was designed primarily as check to these problems. The study used Nigeria Demographic and Health Survey (NDHS), 2008 data. A total of 18,250 (6,894 urban and 11,356 rural) adults responded to questions essential for the estimation of maternal mortality. The P/F ratio method was used to adjust the total fertility rates (TFR) in urban and rural areas. Thereafter, the life-time risks of maternal deaths (LTRMD) were estimated for the two areas. These were later converted to maternal mortality ratio (MMR). Data analyses revealed that the adjusted total fertility rates for urban and rural areas were 5.26 and 7.12 respectively. The LTRMD in urban was 0.0221 (1 in 45) whereas, in rural area it was 0.0309 (1 in 32). These results correspond to MMR of 424/100,000 and 440/100,000 live births in urban and rural areas respectfully. These are not far from the national estimate of 436/100,000 live births as evidence in this study. This method provided a robust estimate of MMR in both urban and rural areas and shows that the MMR in Nigeria is reducing. However, the figures at the two locations are still high. Government and international agencies should put appropriate mechanisms in place for further reduction in the prevalence.
A model for measuring association between bivariate censored outcomes
(Medwell Journals, 2010) Fagbamigbe, A. F.; Adebowale, A. S.
The dependence between two random variables is completely described by their bivariate distribution. Bivariate sunrival analysis arises in the time to events analysis of measurements that are paired. Although, there are several comistent estimators of the bivariate distribution function, an efficient and consistent estimation has proven to be a difficult problem. It is of interest to determine if it exists, the possible association between pairs of variables, both of which are subject to censoring with recurrence times of kidney infection as a case study. Copula models which is one of the existing methods of measuring the possible association between bivariate cemored variables were reviewed. The overall average recurrence time and its standard deviation are 102 and 131, respectively though the recurrence time in the first kidney has average and standard deviation of 112 and 144.01, respectively whle the average and standard deviation of recurrence time in the second kidney recurrence time is 92 and 117.20, respectively. The study also showed that the modal recurrence time in the 2 kidneys is 42. The correlation between infection recurrence in the pairs of kidneys was found to be 0.268 with 95% confidential interval of (-01854985,07206918).
Investigation of a measles outbreak in a Rural Nigerian community – the aladura experience
(Academic Journals, 2010-03) Adeoye, I. A.; Dairo, M. D.; Adekunle, L. V.; Adedokun, H. O.; Makanjuola, J.
The global burden of measles has remained a public health challenge. Worldwide, measles is the fifth leading cause of death among under-five children with an estimate of 197,000 deaths in 2007. In Nigeria, measles is an important cause of childhood morbidity and mortality. Measles outbreaks have been increasingly common in the country with 30, 194 and 256 outbreaks reported in 2006, 2007 and 2008 respectively. This paper describes the investigation, findings and mitigation efforts of a measles outbreak in Ogunmakin, a rural community in South-western Nigeria from 7th January to 15th February 2009. The study design was descriptive and cross-sectional in nature. The investigation was multidisciplinary in nature performed based on the national guidelines for investigating a measles outbreak. This involved data and blood sample collection from the initial cases, notification of the local government health authority, active search and line listing of cases from other health facilities. A household survey was conducted to find additional cases as well as to define the extent of the outbreak. Qualitative techniques were also employed to explore the issues associated with the uptake of immunization in the community. A total of 29 measles cases were identified, all were less than five years old. There were two deaths giving a case fatality rate of 6.9%. Majority of the cases (96.5%) were not immunized against measles. The epidemic spanned 5 weeks with majority of the cases occurring in the 2nd week. There was a clustering of cases in one of the five quarters/settlement – Otesile. The measles immunization coverage for the community was estimated as 22.9%. The stated reasons for the poor uptake of immunization were lack of time, not regarding it as important. A total of 432 children aged 9 months to 15 years received measles antigen during the response vaccination campaign. The measles outbreak in Ogunmakin village was due to low routine immunization coverage resulting in an accumulation of susceptible children. Socio-cultural factors and weak health infrastructure contribute significantly to the low uptake of immunization. There is the need mobilized the entire community on the importance of immunization as well as strengthen the provision of routine immunization.
HIV/AIDS-related stigma and access to HIV treatments by people living with HIV/AIDS: A case study of selected states in North-West Nigeria
(Elsevier Urban & Partner, 2011) Akpa, O. M.; Adeolu-Olaiyaa, V.; Olusegun-Odebiri, C. A.; Aganaba, D.
Objectives: To study the prevalence of HIV-related stigma and the effect of stigma on HIV treatment adoption among PLWHA attending HIV treatment locations in some selected states in the North-West geopolitical zone of Nigeria. Methods: A cross-sectional survey was conducted (using structured questionnaires) among PLWHA in three selected states in the North-West geopolitical zone of Nigeria and Abuja, the Federal Capital Territory (FCT). The multiple logistic regressions analysis was used to determine factors associated with HIV-related stigma and adoption of HIV treatment. Results: It was found that 71(21.3%), 88(26.3%) and 43(12.8%) of the participants were facing HIV-related stigma from their place of works, the public and their family members. Also, the results of the logistic regressions show that PLWHA who have no formal education and those with primary education were less likely to face stigma from the public (OR-0.212; 95% CI-0.064–0.702; p < 0.05) and their employers (OR-0.236; 95% CI-0.072–0.775; p < 0.05) respectively. Conclusion: Although majority of the participants claimed not to be facing any form of HIV-related stigma, the prevalence of HIV-related stigma observed (job related stigma – 21.3%, stigma from the public – 26.3% and stigma from family members-12.8%) among the participants in this study still calls for concern.
Small-Sample Corrected Akaike Information Criterion: An appropriate statistical tool for ranking of adsorption isotherm models
(Elsevier B.V., 2011) Akpa, O. M.; Unuabonah, E. I.
Ranking of seven equilibrium isotherm models with various numbers of parameters (Langmuir, Freundlich, Redlich–Peterson, Sip, Langmuir–Freundlich, Fritz–Schlunder-3 parameter and Fritz–Schlunder-4 parameter)for the adsorption of Cu2+ and Cd2+ onto Bentonite and modified Bentonite clay was done using the smallsample-corrected Akaike information criterion (AICc). It was observed that the Freundlich model ranked first among the adsorption isotherm models considered. Inmost cases, using the AICc, the Langmuir model was ranked the second best isotherm model. Modification of Geothite, Humic acid, and Goethite+Humic acid with increase in temperature was observed to affect the Relative Akaike Weight (RAW) which describes the performance of adsorption models relative to the adsorption model with the minimum AICc estimate. The AICc was found to rank adsorption isotherm models better than error functions because it is more sensitive to model deviations and takes into consideration the number of parameters in an equilibrium isotherm model. AICc was found to be more reliable in resolving very close performance of adsorption isotherms. This study showed that the conventional isotherm model, Freundlich, is a better model for describing experimental data from adsorption of Cu2+ and Cd2+ onto Bentonite and modified Bentonite adsorbents than models derived from them and having a higher number of parameters.
Modeling the epidemiology and the transmission dynamics of HIV/AIDS in a heterosexual population: basic models and analysis of local stability
(Pushpa Publishing House, 2011) Akpa, O. M.; Oyeloja, B. A.
Heterosexual dynamical models for HIV transmission in Nigeria are studied with the population divided into Susceptible, Infectious and AIDS compartments each for the male and female subpopulations. We assume that the AIDS compartment does not participate in sexual activities that could further cause infections among the susceptibles. The disease free and the endemic equilibria of the systems are studied analytically. The asymptotic behaviour of the endemic conditions of the systems is studied numerically. It is observed that both the disease free and the endemic equilibria for the systems are Locally Asymptotically Stable (LAS). Given uniform parameters (except for the global parameters), infections among females are observed to be relatively higher than infections among males.
Gender variation in self-reported likelihood of HIV infection in comparison with HIV test results in rural and urban Nigeria
(Biomed Central, 2011) Fagbamigbe, A. F.; Akinyemi, J. O.; Adedokun, B. O.; Bamgboye, E. A.
Background: Behaviour change which is highly influenced by risk perception is a major challenge that HIV prevention efforts need to confront. In this study, we examined the validity of self-reported likelihood of HIV infection among rural and urban reproductive age group Nigerians. Methods: This is a cross-sectional study of a nationally representative sample of Nigerians. We investigated the concordance between self-reported likelihood of HIV and actual results of HIV test. Multivariate logistic regression analysis was used to assess whether selected respondents’ characteristics affect the validity of self-reports. Results: The HIV prevalence in the urban population was 3.8% (3.1% among males and 4.6% among females) and 3.5% in the rural areas (3.4% among males and 3.7% among females). Almost all the respondents who claimed they have high chances of being infected with HIV actually tested negative (91.6% in urban and 97.9% in rural areas). In contrast, only 8.5% in urban areas and 2.1% in rural areas, of those who claimed high chances of been HIV infected were actually HIV positive. About 2.9% and 4.3% from urban and rural areas respectively tested positive although they claimed very low chances of HIV infection. Age, gender, education and residence are factors associated with validity of respondents’ self-perceived risk of HIV infection. Conclusion: Self-perceived HIV risk is poorly sensitive and moderately specific in the prediction of HIV status. There are differences in the validity of self-perceived risk of HIV across rural and urban populations.
A comparative analysis of condom use among unmarried youths in rural community in Nigeria
(Scientific & Academic Publishing, 2011) Fagbamigbe, A. F.; Adebowale, A. S.; Olaniyan, F. A.
Globally, youths are more sexually active than any subgroup of the population. In Nigeria, the prevalence of condom use among youths is low. This study explored and compared condom use among in-school youths and out-of-school youths in south western Nigeria. This population based study used multistage random sampling technique to select eligible 600 youths aged 15-24 years which included 300 high school students and 300 out-of-school youths in Ekiti West Local Government area of Ekiti state, Nigeria. Descriptive statistics, t-test, chi square test and logistic regression were used for analysis. The mean age of in-school youths and out of school youths were 18.1±2.2 years and 19.0±2.7 years respectively. Overall, 35.5% of all sexually active respondents, 29.8% in-school and 40.8% out-of-school youths reported to have ever used condom during sexual intercourse (p<0.05) The study concluded that although, condom use is low across the study population, but higher among out-of-school youths. Youths aged 15-24 should be given free access to condom particularly the in-school youths.
Modelling morbidity related absenteeism among workers in University of Ibadan Community, Nigeria: Poisson regression
(Academic Journals, 2011) Apau, G. S.; Fagbamigbe, A. F.; Adebowale, S. A.; Bamgboye, E. A.
Globally, sickness absenteeism is a contemporary public health problem, particularly in developing countries. However, very few studies had addressed the theoretical and methodological aspects of health related absenteeism among University workers. A retrospective study of sickness records of 4447 employees of University of Ibadan made available at the University Staff Clinic (Jaja). The health records of each staff for the whole 12 months in 2007 were reviewed. Data analysis was performed using descriptive statistics and Poisson distribution model was used in the data modeling. The prevalence of sick-off leave at the staff clinic was 4.7%. Also, 12.4% of all the staff had been sick at least once during the study period. There was a slight differential in absent rate by sex, age, marital status and years of service. However, differential existed in absent rate among subgroup of workers by different occupational groups and staff category. Majority of the spells lasted for between one and two days. The Poisson regression model showed that staff category and occupational group are the only predictors of days sick-off. Among the dependent variables considered, only sick-off days followed Poisson distribution model. Also, Poisson regression model is adequate to describe and predict the pattern of sickness absenteeism in the study area.
Contraceptive use: implication for completed fertility, parity progression and maternal nutritional status in Nigeria
(Women's Health and Action Research Centre, 2011) Adebowale, S. A.; Fagbamigbe, F. A.; Bamgboye, E. A.
The study identified socio-demographic factors influencing contraceptive use while using nutritional status, completed fertility and parity progression as key variables. NDHS, 2008 dataset on married women aged 45-49 was used. Chi-square, ordinary linear and logistic regression models were used for the analysis. The mean age of the women and CEB were 46.8±1.5 years and 6.9±3.1 respectively. About 26.0% of the women ever used contraception, while 9.0% of the women were underweight. Parity progression from parity 0 to 4 was consistently higher among never-users than women who ever used contraception. The tempo changes for all parities above four as ever-users now progress at lower rate during these periods. The completed fertility and the risk of undernourishment were significantly higher among never users of contraception than ever users. The level of risk persists even when the potential confounding variables were used as control