Rationale:
Black Africans have reduced FVC compared with white
persons, but the prevalence and determinants of reduced values are
not well understood.
Objectives:
To evaluate the prevalence and factors leading to
reduced FVC in a Nigerian population and to examine current
theories regarding the determinants of this difference.
Methods:
We studied the ventilatory function of 883 adults aged
40 years or older participating in the Burden of Obstructive Lung
DiseaseStudyinIle-Ife,Nigeria.Respondentscompletedpre-andpost-
bronchodilator spirometry test and provided information on their
smoking history, respiratory symptoms, risk factors, and diagnoses,
including anthropometric details. We used standard categories to
de
fi
ne body mass index as either underweight, normal, overweight, or
obese. We de
fi
ned reduced FVC as a post-bronchodilator FVC below
the lower limit of normal using National Health and Nutrition
Examination Survey (NHANES) equations, Global Lung Function
Initiative 2012 equations, and local reference equations based on
nonsmoking study participants without a respiratory diagnosis. We
fi
t
multivariate linear regression models to FVC as a continuous measure,
adjusting for age, sex, height, and other confounders.
Results:
The prevalence of reduced FVC was 70.4% for men
and 72.8% for women when using NHANES values for white
Americans, 17.8% for men and 14.4% for women using
NHANES equations for African Americans, and 15.5% for men
and 20.5% for women using the Global Lung Function Initiative
2012 equations. Using the equations derived from nonsmoking
respondents in the survey without a respiratory diagnosis, the
prevalence of reduced FVC was less than 4% for both men
and women. FVC was lower in participants who had less
than 7 years of education (FVC,
2
96 ml; 95% con
fi
dence
interval [CI],
2
172 to
2
19), were underweight (FVC,
2
269 ml;
95% CI,
2
464 to
2
73), were overweight (FVC,
2
132 ml;
95% CI,
2
219 to
2
46), and were obese (FVC,
2
222 ml; 95%
CI,
2
332 to
2
112).
Conclusions:
There is a wide variation in the prevalence of
reduced FVC based on the reference standard used. This
variation is not satisfactorily explained by factors thought to
affect FVC within individual populations. However, the
prevalence strongly associates with both education level and
body mass index in this population, regardless of the speci
fi
c
standard used.