Can anyone help me identify which are the Dependent variables and the Independen

Question

Can anyone help me identify which are the Dependent variables and the Independent variables in the folloing research ?

Introduction

Atrial fibrillation (AF) and its sequelae have become a significant public health burden and cost factor in the health care system due to an increasing prevalence in aging populations [1]. Although individuals with AF are at high risk of incident stroke and heart failure, an increased risk of death remains after accounting for these serious complications and other cardiovascular comorbidities. Numerous studies have found that depression predicts prognosis in cardiac conditions such as stable coronary artery disease, myocardial infarction, and heart failure [2]. Evidence suggests that depressive symptoms in AF are related to the recurrence of AF episodes [3] and the occurrence of complications of AF such as heart failure and death in the clinical setting [4]. From other cardiovascular diseases we know that psychosocial distress may influence hemodynamics, vascular function, autonomic tone, inflammatory activity, and hemostasis [5], [6], [7], all of which play a role in the pathogenesis and complications of AF.

Initial smaller investigations in AF indicate that the disease is frequently accompanied by depressive symptoms which may impact physical activity and quality of life in AF patients [8], [3], [9]. However, overall there is a critical lack of knowledge regarding the type and extent of psychological distress and its consequences in patients diagnosed with AF [10]. Data in individuals with AF in the general population are rare. We hypothesized that in ambulatory individuals from the general population depression is more frequent in AF independent of age, sex and cardiovascular comorbidities.

Methods

Study participants

The Gutenberg Health Study constitutes a cohort of a randomly selected population-based sample of the region of Mainz/Mainz-Bingen aged 35 to 74 years with a proportion of 49% women. It was incepted in 2007 at the Department of Medicine 2, University Medical Center Mainz. During the baseline clinic visit comprehensive information on cardiovascular risk factors is collected by anthropometric measures and standardized computer-assisted interview. Classical cardiovascular risk factors were defined as follows: Smoking status comprised the categories non-smokers (never smokers and former smokers) and smokers. Diabetes mellitus was diagnosed when individuals reported a physician diagnosis of diabetes and/or a fasting blood glucose concentration of 126 mg/dL (minimum 8-hour fast) or a blood glucose level of 200 mg/dL at any time was measured on site. Dyslipidemia was defined based on a physician's diagnosis of dyslipidemia and/or a low-density-lipoprotein/high-density-lipoprotein cholesterol ratio of >3.5. The definition of hypertension comprised anti-hypertensive drug treatment and/or a mean systolic blood pressure of 140 mmHg and/or a mean diastolic blood pressure of 90 mmHg.

Myocardial infarction was assessed by self-report. Heart failure was defined by self-reported treatment of heart failure within the last 12 months.

Depression was assessed by the Patient Health Questionnaire (PHQ-9), which quantifies the frequency of being bothered by each of the 9 diagnostic criteria of Major Depression over the past 2 weeks. Responses are summed to create a score between 0 and 27 points. A PHQ-9 sum score of 10 was used for the definition of caseness for depression [11]. The somatic and cognitive dimensions of depression were defined according to prior studies [12], [13], [14], [15], [16]. Four PHQ-9 items related to problems with sleep, fatigability, appetite, and psychomotor agitation/retardation were classified as somatic depressive symptoms, whereas 5 items, related to lack of interest, depressed mood, negative feelings about self, concentration problems and suicidal ideation, were classified as cognitive depressive symptoms. During the computer-assisted personal interview participants were asked whether they had ever received the definite diagnosis of any depressive disorder by a physician (medical history of lifetime diagnosis of any depressive disorder).

Socioeconomic status was evaluated using Lampert's and Kroll's Score of socioeconomic status that ranges from 3 to 27 with 3 indicating the lowest socioeconomic status.

The diagnosis of AF was made based on a history of AF reported by the participant and/or the electrocardiographic documentation (GE Cardiosoft®) of AF or atrial flutter [17]. At least two physicians with cardiology training and experience in electrocardiogram (ECG) reading had to agree on the diagnosis.

C-reactive protein (CRP) was measured from fasting blood samples by a standardized method through particle enhanced turbidimetric immunoassay (Dimension® Chemistry System, Dade Behring).

All authors have read and approved the manuscript as written.

Statistical methods

Data were analyzed for the first 10,000 consecutive GHS individuals. We did not require complete case analysis so that in some analyses the total number of individuals may be smaller than the total sample size. Demographics and prevalence of risk factors for the study sample weighted for the population of the region Mainz/Mainz-Bingen are also provided in the supplement. Since depression may depend on awareness of the disease AF, we also present data separately for individuals with a prior diagnosis of AF and participants with a first diagnosis of AF on the study ECG. In logistic regression models, depression and its dimensions were related to atrial fibrillation. Models were adjusted for age and sex as well as for age, sex and atrial fibrillation risk factors body mass index, systolic blood pressure, antihypertensive medication, diabetes, current smoking, dyslipidemia and a family history of myocardial infarction. Model R2 values were calculated. Additional models were calculated adjusting for heart failure, partnership status or CRP. We tested for interactions of depressive symptoms in association with AF by age and sex.

To understand whether depression and its symptom dimensions are mediated by other psychosocial conditions, cardiac function or inflammatory activity, we describe depressive symptoms according to partnership, manifest heart failure, and median CRP concentrations. Due to expectedly lower numbers in the subgroup of individuals with AF we performed analyses for very good/good versus fair/bad self-rated physical and mental health status.

In secondary analyses we also performed multivariable regression analyses of depressive symptom dimensions in relation to self-rated physical and mental health status for individuals with AF.

We assumed a threshold of P<0.05 for statistical significance. As this is an explorative study no adjustments for multiple testing have been performed. P values are given for descriptive reasons.

Explanation / Answer

Answer:

For the given statistical model, there are so many variables used for the analysis. The multivariate regression model is used to analyse the effects, relationships and interactions between different variables. For the given scenario, the dependent variable is given as the atrial fibrillation risk (AF) while the independent variables for this study are given as age, sex, body mass index, systolic blood pressure, antihypertensive medication, diabetes, current smoking, dyslipidemia and a family history of myocardial infarction. Also, there are some other variables used in the secondary analysis of the research study. The ordinal, nominal and ratio scales of variables are used for this study.

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