Chronic Airflow Obstruction in a Black African Population: Results of BOLD Study, Ile-Ife, Nigeria

Abstract

Global estimates suggest that Chronic Obstructive Pulmonary Disease (COPD) is emerging as a leading cause of death in developing countries but there are few spirometry-based general population data on its prevalence and risk factors in sub-Saharan Africa. We used the Burden of Obstructive Lung Disease (BOLD) protocol to select a representative sample of adults aged 40 years and above in Ile-Ife, Nigeria. All the participants underwent spirometry and provided information on smoking history, biomass and occupational exposures as well as diagnosed respiratory diseases and symptoms. Chronic Airflow Obstruction (CAO) was defined as the ratio of post-bronchodilator (BD) one second Forced Expiratory Volume (FEV₁) to Forced Vital Capacity (FVC) below the lower limit of normal (LLN) of the population distribution for FEV₁/FVC.

The overall prevalence of obstruction (post-BD FEV₁/FVC < LLN) was 7.7% (2.7% above LLN) using Global Lung Function Initiative (GLI) equations. It was associated with few respiratory symptoms; 0.3% reported a previous doctor-diagnosed chronic bronchitis, emphysema or COPD. Independent predictors included a lack of education (OR 2·5, 95% CI: 1.0, 6.4) and a diagnosis of either TB (OR 23.4, 95% CI: 2.0, 278.6) or asthma (OR 35.4, 95%CI: 4.9, 255.8). There was no association with the use of firewood or coal for cooking or heating. The vast majority of this population (89%) are never smokers. We conclude that the prevalence of CAO is low in Ile-Ife, Nigeria and unrelated to biomass exposure. The key independent predictors are poor education, and previous diagnosis of tuberculosis or asthma.

Keywords:

• CAO
• COPD
• Nigeria
• prevalence
• spirometry

Acknowledgments

We thank the members of BOLD Coordinating Centre at Imperial College London, including Anamika Jithoo, Sonia Coton, Hadia Azhar, Bernet Kato and James Potts for their assistance with spirometry training, quality control and data management for the study. We are also highly indebted to the American Thoracic Society for initiating this work through the global research training program (MECOR). We appreciate the invaluable comments from William Vollmer of Kaiser Permanente Center for Health Research, William Beckett of Harvard Medical School, Boston and Jane Carter of International Union Against Tuberculosis and Lung Disease (IUATLD) in the writing of this manuscript.

Funding

We wish to thank the Wellcome Trust for the Master's training fellowship awarded to the corresponding author in support for this research (REF: 089405/Z/09/Z).

Declaration of Interest Statement

DOO reports grant from the Wellcome Trust, PGB reports grants from Wellcome Trust, during the conduct of the study; grants from MRC, MRC-PHE, Wellcome Trust, Glaxo Smithkline, and BLF outside the submitted work. GEE, ASB, LG and OOA report no relevant conflict of interest. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication.

The authors alone are responsible for the content and writing of the paper.