|Year : 2016 | Volume
| Issue : 2 | Page : 59-64
A review of population-based studies on diabetes mellitus in Nigeria
Tukur Dahiru, Alhaji A Aliyu, AU Shehu
Department of Community Medicine, Ahmadu Bello University, Zaria, Nigeria
|Date of Submission||27-May-2015|
|Date of Acceptance||26-Apr-2016|
|Date of Web Publication||21-Jun-2016|
Dr. Tukur Dahiru
Department of Community Medicine, Ahmadu Bello University, Zaria
Diabetes is a major cause of morbidity and mortality both in developing and developed countries. The incidence is rising rapidly with sub-Saharan Africa experiencing the largest percentage increase between 2013 and 2035. Nigeria has the largest number of people with the disease, yet information on the diabetes mellitus for policy and programming is fragmentary. Therefore, the purpose of this study to systematically identify population-based studies on diabetes in Nigeria and to determine the prevalence and sex differential. A literature search of the PubMed database was conducted of published research between 1990 and 2013 using the medical subject headings "diabetes mellitus" and "Nigeria." The search was done at the end of 2013 which returned 741 hits. A manual search for additional studies was performed using references cited in the original articles. Some authors were contacted whose full-text publications were not available on the PubMed database or freely on the internet. Twenty population-based studies that had been conducted on the prevalence of diabetes in Nigeria between 1990 and December 2013 that satisfied the inclusion criteria were identified. The prevalence of diabetes ranged from 0.8% to 11% involving both urban and rural populations, with varying sampling schemes, one study reported a traditional population with very low prevalence of diabetes and highly specific populations as well. The review revealed a generally low prevalence (<10%) of diabetes in Nigeria. It also found that there is dearth of literature on diabetes. There is the need to undertake a nationally-representative survey to assess the burden of diabetes in general population.
Keywords: Diabetes, Nigeria, prevalence, review
|How to cite this article:|
Dahiru T, Aliyu AA, Shehu A U. A review of population-based studies on diabetes mellitus in Nigeria. Sub-Saharan Afr J Med 2016;3:59-64
|How to cite this URL:|
Dahiru T, Aliyu AA, Shehu A U. A review of population-based studies on diabetes mellitus in Nigeria. Sub-Saharan Afr J Med [serial online] 2016 [cited 2019 Jan 18];3:59-64. Available from: http://www.ssajm.org/text.asp?2016/3/2/59/184351
| Introduction|| |
Diabetes is one the important noncommunicable diseases (NCDs) that is rapidly attracting the attention of the international medical community, culminating in a United Nations political declaration on NCDs in September 2011 with follow-up meeting on Political Declaration of the High-level meeting of the General Assembly on the Prevention and Control of NCDs in May 20131. , Globally, the burden of diabetes is rapidly increasing. According to International Diabetes Federation (IDF) Diabetes Atlas More Details, by end of 2013, there were 382 million (or 8.3% of adult world population) people worldwide with diabetes of which 80% live in low-and-middle-income countries; this number is estimated to reach 592 million in <25 years (by 2035). Currently, sub-Saharan Africa is estimated to have 20 million people with diabetes, about 62% are not diagnosed and the number is expected to reach 41.4 million by 2035 or an increase of 109.1%. In sub-Saharan Africa, Nigeria has the highest number of people with diabetes with an estimated 3.9 million people (or an extrapolated prevalence of 4.99%) of the adult population aged 20-79-year-old.  Further, in terms of morbidity, diabetes contributes to the development of heart disease, renal disease, pneumonia, bacteremia, and tuberculosis (TB). ,,,,, It is known that people with diabetes are 3 times more likely to develop tuberculosis and approximately 15% of TB globally is thought to have background diabetes as a predisposing factor. This situation of the double burden of disease particularly in developing countries put diabetes to compete for resources as well as political commitment. 
Studies conducted in Nigeria indicated that the prevalence of diabetes ranged from low level of 0.8% among adults in rural highland dwellers to over 7% in urban Lagos with an average of 2.2% nationally.  As already pointed out, the sixth edition of IDF diabetes Atlas, shows that Nigeria is the leading country in Africa in terms of the number of people with diabetes, 3.9 million had diabetes with 105,091 diabetes-related deaths in 2013 which is estimated to increase annually by 125,000 between 2010 and 2030 even though the prevalence of 4.99% is far less than that of Reunion (15.38%), Seychelles (12.11%), Gabon (10.71%), Zimbabwe (9.73%), and South Africa (9.27%); in addition, there are still about 1.8 million Nigerians with undiagnosed diabetes in 2013. 
The aim of this review was to identify population-based studies on diabetes in Nigeria, to determine the prevalence, examine the sex and urban/rural difference in these rates and temporal trends in the prevalence.
| Methods|| |
We conducted a literature search of PubMed database from 1990 to 2013 using the medical subject headings "diabetes mellitus" and "Nigeria." The search was done on 31 st December 2013. A manual search for additional studies was performed using references cited in the original articles. In addition, one of us (TD) contacted some authors whose published works are not freely available on the internet. The authors screened titles and abstracts, and then two of us (TD, AAA) screened abstracts of retrieved references for potentially relevant studies. We obtained the full texts of potentially relevant studies, and one of us (TD) scrutinized these papers independently.
The review included studies that fulfilled the following criteria: Community-based and/or population-based; cross-sectional in design either employing random or nonrandom sample selection; reported prevalence of diabetes mellitus, conducted in apparently healthy, nonpregnant subjects; subjects are adults (i.e. aged ≥15 years) and residing within Nigeria; involving both men and women; employed any of the World Health Organization (WHO's) diagnostic criteria or the equivalent criteria of the American Diabetic Association for diabetes mellitus. Diabetes mellitus was defined as fasting plasma glucose level ≥7 mmol/l (126 mg/dl) or random plasma glucose level ≥11.1 mmol/L (199.8 mg/dl)  or HbA1c ≥6.5%. Those studies excluded from this review included: Self-report of diabetes, hospital-based studies, a study among Nigerians in diaspora, studies which aimed to determine the prevalence of metabolic syndrome since the diagnostic criterion for diabetes is different from that recommended by the WHO. Variables extracted included the name of first author, year of publication of survey, age range of participants, sampling methods, response rate, sample size, type of sample, and diagnostic criteria; the prevalence of diabetes (unadjusted, age-adjusted, and by sex) as well as mean blood glucose level were extracted.
| Results|| |
The PubMed search returned 741 hits, nineteen population-based studies conducted to determine the prevalence of diabetes in Nigeria between 1990 and December 2013 that satisfied the inclusion criteria were identified and included in this review. ,,,,,,,,,,,,,,,,,, We contacted the authors of three papers for the full-text; ,, one of whom is the authors of this study (TD) and one study that reported the prevalence of diabetes but did not report the diagnostic criteria was excluded.  [Table 1] shows a summary of the characteristics of the studies and participants as well as methods used for blood glucose measurement. The earliest studies included in this study were reported in 1997 while the latest was in the October-December 2013 edition of the journal. The sample size for individual papers in these studies ranged from 199 to 58567 with a response rate between 67.1% and 100%. One study by Owoaje et al. used the 1985 WHO definition criteria.  [Table 2] shows the mean blood glucose levels reported from the included studies. The mean fasting blood glucose/blood glucose ranged from 4.2 to 8.9 mmol/L. [Table 3] shows the prevalence of diabetes mellitus, the prevalence ranged from 0.3% to 10.5% (among women) and from 0.5% to 11.6% (among men); only one study reported age-standardized prevalence.
| Discussion|| |
This review identified nineteen population-based studies conducted within Nigeria between 1990 and 2013. Fully aware of the rapidly increasing population (alongside aging of the population) in Nigeria, noncommunicable diseases deserve more priority in terms of research. However, as this review shows, in the 23-year period there have been few research outputs implying priority is not accorded to noncommunicable diseases research in Nigeria and of particular diabetes mellitus. So far, the Federal Ministry of Health of Nigeria was able to conduct a nationally-representative study on noncommunicable disease in 1992 and till date no repeat has been conducted.  This review brings to the fore again, that with urbanization and epidemiological transition societies that were considered to be free of chronic noncommunicable disease (diabetes mellitus in this case) are not actually free. This is the case of two studies by Sabir et al. in 2011  and Sabir et al. in 2013.  The earlier study (reported in 2011) among Fulani nomads of Sokoto metropolis recorded a prevalence of 4.6% while the prevalence among the "traditional rural Fulani nomads" who still live with the herds in the bush revealed a prevalence of 0.8% indicating their continued attachment to traditional lifestyle while their counterparts in urbanized cosmopolitan Sokoto metropolis have adopted the western lifestyle such as sedentary lifestyle, intake of high-calorie food, and smoking.
There are issues related to the quality of the studies documented here. First, there is the issue of representativeness in terms of sampling of participants; seven studies indicated the type of sampling employed which on further scrutiny cast doubt on its utilization in the study setting as no sufficient details were provided; perhaps with the possible exception of studies by Hendriks  and Nyenwe.  A second quality issue that is related to sampling methodology is sample size; this ranged from 199 to 58567 and for most of the studies except those by Ogah  and Hendriks,  no rationale was provided for choosing such sample size. The third quality issue is that of standardized prevalence rates which are required to compare prevalence across studies. Only the study by Nyenwe et al.  reported standardized prevalence among males and females. While some studies used the WHO 1985 diagnostic criteria others used the 2003 criteria. The concern here, although methodologically correct, is that comparison is difficult when using different diagnostic benchmarks. The study by Nwafor and Owhoji did not report on the diagnostic criteria used. 
Despite these limitations, there are important findings worth mentioning. First, the overall prevalence based on these studies shows range from 0.8% to 11%; generally <10% indicating that different population groups are in different stages of epidemiological transition. The prevalence rates reported by Ekpenyong and Ige are among highly select and older populations of University staff and civil servants in highly urbanized societies. , Second, the prevalence with respect to gender indicates that both females and males are similarly affected. In four studies, the prevalence among women is higher while in another four it is lower.
| Conclusion|| |
Despite the limitations associated with the limited number of research on assessing the burden of diabetes mellitus in the general Nigerian population, the review found that the prevalence of diabetes in the general population is low (<10%); that studies are fragmentary and a nationally-representative rate not available in public domain. This underscores the urgent need to undertake a nationally-representative, standardized, and more scientifically rigorous inquiry on diabetes mellitus. Such inquiries should be regular and standardized in its methodology to allow time-trend analysis, which is necessary for policy formulation and reviews. Such inquiry can either be a separate and independent one or be part of the more regular demographic and health surveys currently going on in the country. Knowledge of factors associated with diabetes from such studies will inform prevention and control strategies to reduce both social and economic costs of the disease.
Financial Support and Sponsorship
Conflicts of Interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]