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Assessment of diabetes and prediabetes prevalence and predictors by HbA1c in a population from sub-Saharan Africa with a high proportion of anemia: a prospective cross-sectional study
  1. Nikolai Carl Hodel1,2,
  2. Ali Hamad3,
  3. Klaus Reither2,3,
  4. Grace Mwangoka3,
  5. Irene Kasella4,
  6. Claudia Praehauser1,
  7. Salim Abdulla3,
  8. Christoph F R Hatz2,5,
  9. Michael Mayr1
  1. 1Medical Outpatient Department, Universitätsspital Basel, Basel, Switzerland
  2. 2Swiss Tropical and Public Health Institute, Basel, Switzerland
  3. 3Ifakara Health Institute, Dar es Salaam, Tanzania
  4. 4Medical Outpatient Department, Bagamoyo District Hospital, Bagamoyo, Tanzania
  5. 5Cantonal Hospital Sankt Gallen, St. Gallen, Switzerland
  1. Correspondence to Dr Michael Mayr; Michael.mayr{at}


Introduction Epidemiological data about diabetes mellitus (DM) for sub-Saharan Africa (SSA) are scarce and the utility of glycated hemoglobin (HbA1c) to diagnose DM is uncertain in African populations with a high proportion of anemia.

Research design and methods In a cross-sectional study, age-adjusted prevalence rates and predictors for DM and pre-DM were prospectively assessed by HbA1c in a semirural walk-in population of Tanzania (n=992). Predictors for DM were calculated by logistic regression. Correlations between HbA1c, hemoglobin, and blood glucose levels were done by Pearson’s correlation.

Results Overall, DM and pre-DM prevalence rates were 6.8% (95% CI 5.3 to 8.5) and 25% (95% CI 22.8 to 28.3), respectively. There was an increase in DM prevalence in patients 50–59 (14.9%; 95% CI 9.1 to 22.5), ≥60 years old (18.5%; 95% CI 12.2 to 26.2) and in patients with overweight (9.3%; 95% CI 5.9 to 13.7), obesity (10.9%; 95% CI 6.9 to 16) compared with patients 18–29 years old (2.2%; 95% CI 0.9 to 4.4) (p<0.001) and to normal-weight patients (3.6%; 95% CI 2.1 to 5.6) (p<0.01), respectively. Age (OR 1.08, 95% CI 1.05 to 1.12; p<0.001), body mass index (BMI) (OR 1.10, 95% CI 1.04 to 1.16; p<0.001), and acute infection (OR 3.46, 95% CI 1.02 to 10.8; p=0.038) were predictors for DM. Comparing patients with a BMI of 20 kg/m2 and a BMI of 35 kg/m2, the relative risk for DM increases in average by 2.12-fold (range 1.91–2.24) across the age groups. Comparing patients 20 years old with patients 70 years old, the relative risk for DM increases in average 9.7-fold (range 8.9–10.4) across the BMI groups. Overall, 333 patients (36%) suffered from anemia. Pearson’s correlation coefficients (r) between HbA1c and hemoglobin was −0.009 (p=0.779), and between HbA1c and fasting blood glucose and random blood glucose, it was 0.775 and 0.622, respectively (p<0.001).

Conclusion We observed a high prevalence of DM and pre-DM, mainly triggered by increasing age and BMI, and provide evidence that HbA1c is suitable to assess DM also in populations of SSA with high proportions of anemia.

Trial registration number NCT03458338.

  • age
  • anemia
  • body mass index
  • diabetes
  • epidemiology
  • HbA1c
  • pre-diabetes
  • risk factors
  • sub-Sahara Africa
  • Tanzania

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  • Contributors All authors made contributions to the study. NCH carried out the fieldwork in the laboratory and clinic, collected, entered and analyzed the data, wrote and illustrated the manuscript. MM designed the study, wrote and revised the manuscript, cleaned data and supervised the fieldwork. AH coordinated the fieldwork and the approval of ethical clearance, informed the Bagamoyo community authorities about the study, translated protocols from English to Swahili, and revised the manuscript. KR coordinated this study onsite and provided important intellectual content input for study design. GM was the laboratory management. IK carried out clinical fieldwork and supported the translation of the protocols. CP entered and cleaned data. SA coordinated the fieldwork and communicated with local authorities. CFRH coordinated the fieldwork, provided important intellectual content input for the study design.

  • Funding The study was supported by a project fund from the University Hospital Basel (VFWAWFPool—section medicine) and the “Freiwillige Akademische Gesellschaft Basel (FAG).”

  • Disclaimer The sponsors did not influence study design, or collection, analysis and interpretation of data, writing of the report or the decision to submit the report for publication.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This study has been approved by the Ethical Committee of the Cantons Basel-Stadt and Basel-Land (University of Basel) Switzerland (No. 220/10), the Institutional Review Board of the Ifakara Health Institute in Tanzania (IHI/IRB/No.20-2010) and by the Tanzanian National Institute for Medical Research (NIMR).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. The original case report forms are stored at the Ifakara Health Institute in Bagamoyo Tanzania. The data and electronic files can be requested by the corresponding authors.

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