Secondary polycythemia in chronic obstructive pulmonary disease: prevalence and risk factors

BMC Pulmonary Medicine

Table 4 Multivariable logistic regression on polycythemia stratified by smoking status

Predictive variable	Former smokers (N = 1266)			Current smokers (N = 662)
Predictive variable	OR	95% CI	P value	OR	95% CI	P value
Sex, male	4.60	2.29–9.25	< 0.0001	2.89	1.42–5.91	0.0036
Race, non-Hispanic white	2.96	1.02–8.59	0.046	3.60	1.56–8.30	0.0026
Age at visit (year)	0.98	0.94–1.02	0.34	0.99	0.95–1.04	0.81
Center, Denver	4.22	1.82–9.75	0.0008	5.59	2.16–14.45	0.0004
Body mass index (kg/m²)	1.01	0.95–1.07	0.80	1.05	0.99–1.12	0.079
Pack-years of smoking	0.99	0.98–1.00	0.21	1.00	0.98–1.01	0.71
FEV₁% predicted	1.00	0.98–1.02	0.90	0.99	0.96–1.01	0.37
DLCO % predicted	0.97	0.95–0.99	0.0016	0.99	0.97–1.01	0.46
Percent emphysema on CT	0.97	0.94–1.01	0.17	1.01	0.96–1.06	0.81
Resting SpO₂
Normal (reference)	1.00			1.00
Mild desaturation	0.93	0.45–1.91	0.84	0.98	0.47–2.07	0.96
Moderate desaturation	0.75	0.27–2.10	0.58	4.00	1.28–12.54	0.017
Severe desaturation	2.10	0.64–6.87	0.22	8.23	1.93–35.07	0.0044
Exercise-induced desaturation	1.19	0.60–2.39	0.62	2.66	1.18–6.01	0.019
LTOT use
No use (reference)	1.00			1.00
Intermittent	0.70	0.16–3.11	0.64	0.28	0.01–11.96	0.51
Nocturnal	0.63	0.26–1.53	0.31	0.47	0.12–1.83	0.28
Continuous	0.24	0.08–0.71	0.0095	0.02	0.00–0.39	0.011
Obstructive sleep apnea
No diagnosis (reference)	1.00			1.00
Without CPAP treatment	0.15	0.01–2.40	0.18	0.96	0.25–3.70	0.95
With CPAP treatment	1.24	0.39–3.95	0.71	0.39	0.08–1.82	0.23
Chronic kidney disease	0.20	0.01–3.29	0.26	0.38	0.02–6.50	0.50

The reported OR and P values are from a single multivariable regression model for each smoking status strata
Bold numbers indicate values with statistical significance P < 0.05
OR odds ratio, CI confidence interval, FEV₁ forced expiratory volume in 1 s, DLCO diffusing capacity of lung for carbon monoxide, SpO₂ oxyhemoglobin saturation measured by oximetry, LTOT long-term oxygen therapy, CPAP continuous positive airway pressure

ISSN: 1471-2466