The Pittsburgh Sleep Quality Index (PSQI) was developed by Buysse and colleagues in 1989. It is a scale that provides a quantitative measurement of sleep quality, distinguishing between good and poor sleep. Its validity and reliability study was conducted in Turkey in 1996 by Agargün and colleagues, with a Cronbach's alpha value of.80. The scale is a four-point Likert type and contains a total of 24 questions, comprising seven components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, use of sleeping pills, and daytime dysfunction. Each component is scored between 0 and 3 based on the frequency of symptoms. The sum of the seven component scores yields the total PSQI score, which ranges from 0 to 21. A total score of 5 or above indicates poor sleep quality and a high level of sleep disturbance.

Self-care will be assessed using the nine-item version of the European Heart Failure Self-Care Behavior Scale (Jaarsma et al., 2003). The validity and reliability of the scale in our country were established by Yıldız and Erci (Yıldız & Erci, 2018). This Likert-type scale measures self-care behaviors such as recognizing symptoms like edema, dyspnea, and fatigue related to HF, adhering to regular medication use, monitoring weight, and restricting fluid and salt intake. Participants are asked to choose one of the following options for each item: completely agree (1), agree (2), undecided (3), disagree (4), or completely disagree (5). A higher total score indicates lower self-care, while a lower score indicates higher self-care. Fit measures for the Structural Equation Model of the scale include RMSEA = 0.047 (CI = 0.00-0.079), AGFI = 0.83, and GFI = 0.91 (Jaarsma et al., 2003). In the study by Yıldız and Erci, the Cronbach's alpha coefficient was reported as 0.82 (Yıldız & Erci,2018)

The Telephone Cognitive Screening Test (T-KogS) was adapted from the ALFI-Mini Mental Assessment test by Newkirk and colleagues. This scale can be administered face-to-face to assess the cognitive functions of Alzheimer's patients or used in situations where face-to-face interviews are not possible (Newkirk et al., 2004). The T-KogS evaluates cognitive domains including orientation (e.g., year, season, day, day of the week, month, state, county, city/town, address, and telephone number), registration and recall (e.g., recalling three objects: apple, table, penny), attention (e.g., writing the word "WORLD" backwards), and language (e.g., repetition of "no if, and, or but," single object naming, and a three-step command). The total score on the T-KogS ranges from 0 to 26, with higher scores indicating better cognitive performance. The Turkish validity and reliability study of the scale was conducted by Naharci et al. in 2020, and the Cronbach's alpha value was reported as 0.73.