Tuberculosis Is Associated with Chronic Hypoxemia among Kenyan Adults (CHAKA): A Case-Control Study

Abstract

Rationale: Data on risk factors for chronic hypoxemia in low- and middle-income countries are lacking. Objectives: We aimed to quantify the association between potential risk factors and chronic hypoxemia among adults hospitalized in Kenya. Methods: A hospital-based, case-control study was conducted at Moi Teaching and Referral Hospital in Eldoret, Kenya. Adult inpatients were screened on admission and enrolled in a 1:2 case-to-control ratio. Cases were patients with chronic hypoxemia, defined as resting oxygen saturation as measured by pulse oximetry (Sp_O2) ⩽ 88% on admission and either 1-month postdischarge Sp_O2 ⩽ 88% or, if they died before follow-up, documented Sp_O2 ⩽ 88% in the 6 months before enrollment. Control subjects were randomly selected, stratified by sex, among nonhypoxemic inpatients. Data were collected using questionnaires and structured chart review. Regression was used to assess the associations between chronic hypoxemia and age, sex, smoking status, biomass fuel use, elevation, and self-reported history of tuberculosis and human immunodeficiency virus diagnosis. Odds ratios (ORs) and 95% confidence intervals (CIs) are reported. Results: We enrolled 108 chronically hypoxemic cases and 240 nonhypoxemic control subjects into our Chronic Hypoxemia among Kenyan Adults (CHAKA) cohort. In multivariable analysis, compared with control subjects, chronically hypoxemic cases had significantly higher odds of older age (OR, 1.2 per 5-year increase [95% CI, 1.1-1.3]), female sex (OR, 3.6 [95% CI, 1.8-7.2]), current or former tobacco use (OR, 4.7 [95% CI, 2.3-9.6]), and prior tuberculosis (OR, 11.8 [95% CI, 4.7-29.6]) but no increase in the odds of human immunodeficiency virus diagnosis and biomass fuel use. Conclusions: These findings highlight the potential impact of prior tuberculosis on chronic lung disease in Kenya and the need for further studies on posttuberculosis lung disease.

Keywords: ambulatory oxygen; chronic hypoxemia; global health; posttuberculosis lung disease; sex differences.

Figure 1.

Study Flow Chart. LTFU =  lost to follow-up; Sp_O2 = oxygen saturation as measured by pulse oximetry.

Figure 2.

Forest plot showing results of multivariable logistic regression model estimating the odds of each exposure, comparing chronically hypoxemic cases with nonhypoxemic control subjects. *Model includes age, gender, HIV testing results, tobacco use, TB status, cooking fuel type, and elevation change. aOR = adjusted odds ratio; CI = confidence interval; HIV = human immunodeficiency virus; TB = tuberculosis.