In order to examine sociodemographic data, education level was categorized into two groups (middle school or lower and high school or higher). Income level was categorized into three groups (≥ 1500 Turkish Liras (TL), 1501 to 3499 TL, and ≤ 3500 TL). Body mass index values were divided into three categories (normal [≤ 24.99 kg/m2], overweight [25 to 29.99 kg/m2], and obese [≥ 30 kg/m2]). Marital status was divided into two groups (single and married). Alcohol intake was also divided into two groups (yes and no). Places where patients were included in the study were divided into two groups (inpatient service and outpatient clinic), and COPD history in their families was categorized into two groups (yes and no). Patients diagnosed with hypertension by a physician and receiving prescription medication were considered as having hypertension. Patients who smoked regularly, at least once a day, were considered as active smokers. Regarding continuous variables, patients were asked to respond to questions such as age, number of people living at home, years of smoking and package numbers, number of admissions to the emergency unit due to COPD during the last year, and number of hospital admissions for COPD.

Saint George’s Respiratory Questionnaire (SGRQ) is a quality of life scale especially developed for the respiratory system that can be used in patients with asthma and COPD, as well as in patients with bronchiectasis and sarcoidosis.12The scale includes the components of symptoms, activity, and effect, and, after scoring, all three components and total quality of life scores are obtained.12The scale is scored from 0 to 100. For each component and for the produced total score, ‘0’ indicates ‘perfect’ and ‘100’ indicates ‘worst’ quality of life.12The validity and reliability of the Turkish version of the scale have been confirmed.12

The Euro Quality of Life Scale (EQ-5D) is a 5-question overall quality of life scale, each consisting of 3 levels.13The scale is composed of 5 dimensions, including mobility, self-care, daily activities, pain, and mood. Higher scores indicate higher quality of life.13The utility of the EQ-5D score was computed using the MVH-A1 algorithm by Dolan.14This algorithm provides a range from −0.594 to +1, where higher values indicate better quality of life. The scale’s validity and reliability have been confirmed in Turkish settings.13

After the administration of the questionnaire and blood sampling, patients were examined in terms of Aix and PWV. A Mobil-O-Graph® (IEM; Stolberg, Germany) device calculated the Aix and PWV by recording oscillometric brachial blood pressure; the cuff subsequently reinflated at the diastolic phase for approximately 10 seconds, recording brachial pulse waves with a high-fidelity pressure sensor.

For 24-hour blood pressure measurement, patients were monitored with a Mobil-O-Graph NG® (IEM; Stolberg, Germany) device. The device was adjusted to perform a 24-hour measurement, once every 15 minutes during the day and once every 30 minutes at night. The next day, at the same time, patient returned the devices. The non-dominant arm was used for measurement, and day and night measurements were adjusted according to the patients’ sleeping and waking hours. Patients were instructed to continue their usual activities and to avoid exhausting exercise. Blood tests were obtained from patients before treatment was administered. Among patients who were hospitalized in the pulmonary diseases service, the questionnaire was applied on the same day. The 24-hour ambulatory blood pressure monitoring (24-h ABPM) measuring device was applied in similar conditions for outpatients.

The results of 24-h ABPM measurement were examined, and, if nighttime average values of systolic and diastolic blood pressures were decreased by 10% or more with respect to day-time average values, this was considered as dipper blood pressure2. When the decrease in blood pressure was less than 10%, it was considered as non-dipper blood pressure pattern.2CRP blood tests were carried out in a Architect C16000 autoanalyzer (Abbott Diag., USA), and the hemogram was analysed in a Mindray BC-6800 whole blood device (Mindray, China).

The ethical approval for the study was obtained from the Izmir Katip Celebi University Interventional Clinical Research Ethics Committee under decision number 164 (date of approval: December 22, 2016). All the procedures in this study were in accordance with the 1975 Helsinki Declaration, updated in 2013. Informed consent was obtained from all participants included in the study.

Statistical analysis was performed using SPSS version 16. In this study, the distribution of the continuous variables were assessed with Kolmogorov-Smirnov test, and the data were not distributed normally. Continuous variables were presented as medians and inter quartile ranges (IQR). Statistical comparison of two independent groups was performed using the Mann Whitney U test. The between-group comparisons of categorical variables were performed using the chi-square test. The strength of association between two continuous variables was assessed using Spearman correlation tests.

Independent effects with respect to the presence of non-dipper blood pressure of the different identifying factors were examined using logistic regression models. The Hosmer-Lemeshow test was used for assesing the model fit. Independent variables with p ≤ 0.10 on bivariate analysis were included in the multivariate logistic regression model with a “backward” elimination method. Due to high correlation between nighttime systolic blood pressure and nighttime mean arterial pressure, only nighttime mean arterial pressure was added to the model. Adjusted coefficients are presented with their 95% confidence intervals. All p values were two-tailed, and p values lower than 0.05 were considered statistically significant.

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