Low FEV(1), 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 (SpO(2)). Such a decrease in SpO(2) and associated factors has not been previously evaluated in a general adult population. AIM: We sought to describe SpO(2) in a sample of adults, at baseline and after 6.3 years, to determine whether factors predicting low SpO(2) in a cross-sectional study were also associated with a decrease in SpO(2) 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 SpO(2) by pulse oximetry was defined as an SpO(2) ≤95%, and SpO(2) decrease was defined as a ≥2% decrease from baseline to below 96%. RESULTS: A total of 139 (4.9%) subjects had a decrease in SpO(2). Forced expiratory volume in 1 second (FEV(1)) <50% of the predicted value and current smoking with a history of ≥10 pack-years were the baseline characteristics most strongly associated with an SpO(2) 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 SpO(2) decrease. A significant decrease in FEV(1) and a new diagnosis of asthma or chronic obstructive pulmonary disease during the observation period most strongly predicted a fall in SpO(2). A lower SpO(2) decrease was observed in those who quit smoking and those who lost weight, but these tendencies were not statistically significant. CONCLUSION: A decrease in SpO(2) 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 SpO(2) decreases in the general population.