Low FEV1, smoking history, and obesity are factors associated with oxygen saturation decrease in an adult population cohort

BACKGROUND Worsening of pulmonary diseases is associated with a decrease in oxygen saturation (SpO2). Such a decrease in SpO2 and associated factors has not been previously evaluated in a general adult population. AIM We sought to describe SpO2 in a sample of adults, at baseline and after 6.3 years, to determine whether factors predicting low SpO2 in a cross-sectional study were also associated with a decrease in SpO2 in this cohort. METHODS As part of the Tromsø Study, 2,822 participants were examined with pulse oximetry in Tromsø 5 (2001/2002) and Tromsø 6 (2007/2008). Low SpO2 by pulse oximetry was defined as an SpO2 ≤ 95%, and SpO2 decrease was defined as a ≥ 2% decrease from baseline to below 96%. RESULTS A total of 139 (4.9%) subjects had a decrease in SpO2. Forced expiratory volume in 1 second (FEV1) <50% of the predicted value and current smoking with a history of ≥ 10 pack-years were the baseline characteristics most strongly associated with an SpO2 decrease in multivariable logistic regression (odds ratio 3.55 [95% confidence interval (CI) 1.60-7.89] and 2.48 [95% CI 1.48-4.15], respectively). Male sex, age, former smoking with a history of ≥ 10 pack-years, body mass index ≥ 30 kg/m(2), and C-reactive protein ≥ 5 mg/L were also significantly associated with an SpO2 decrease. A significant decrease in FEV1 and a new diagnosis of asthma or chronic obstructive pulmonary disease during the observation period most strongly predicted a fall in SpO2. A lower SpO2 decrease was observed in those who quit smoking and those who lost weight, but these tendencies were not statistically significant. CONCLUSION A decrease in SpO2 was most strongly associated with severe airflow limitation and a history of smoking. Smoking cessation and reducing obesity seem to be important measures to target for avoiding SpO2 decreases in the general population.