Sleep plays an important role in human life. Sleep quality is directly related to persons' physical and mental health. The results showed that the sleep quality of hypertensive patients was worse than that of healthy population in China. And 51.40% of respondents had poor sleep quality. Many studies have demonstrated the notion that sleep quality is worse than health people due to abnormal body functions (JinhuanJifang & Xiaoli, 2011; Lan & Yue, 2009; Liu et al., 2016; Osonoi et al., 2015). Continuously rising blood pressure can lead to dysfunction of cerebral cortex and autonomic nerve, which indirectly causes insomnia symptoms such as difficulty in falling asleep, easy to wake up, and restless sleep.
A Chinese population-based study verified that sleep quality was significantly correlated with life quality (JinhuanJifang & Xiaoli, 2011; Lan & Yue, 2009; Liu et al., 2016; Osonoi et al., 2015). Our findings extended the literature suggesting that higher sleep quality score (poor sleep quality) indicates lower life quality in patients with hypertension. Specifically, it was found that subjective sleep quality, sleep disorder, and daytime dysfunction were influencing factors of PCS and MCS. The mechanism of the relationship between sleep quality and life quality has not been clarified due to a lack of confirming evidence, but two aspects must be mainly mentioned here. One reason is that most of the hypertensive patients were elderly people in this study, who might suffer from dizziness, palpitation, and other symptoms due to the pathological changes of the body. The symptoms mentioned above may interfere with sleep quality causing a poor life quality. On the other hand, long-term poor sleep quality can cause or aggravate anxiety and depression, thus affecting the quality of life.
Subjective sleep quality is defined as the retrospective evaluation of the individual's recalled sleep experience, which can be summarized as the overall sleep status (Andrew et al., 2008). Studies conducted in Asia (Hering et al., 2011) and Europe (Hering et al., 2011) have suggested that poor subjective sleep quality is associated with significantly higher odds ratios of hypertension. Our study also found hypertensive patients manifest with a poor subjective sleep quality, which had a negative association with HRQoL including PCS and MCS. We speculated the reason probably related to a series of mental and physical weakness caused by a poor sense of subjective sleep, such as daytime fatigue, bloating, and dizziness, which seriously affects the quality of life. Being a primary indicator of sleep parameters, subjective perception might be helpful to predict sleep quality as well as life quality. Therefore, elderly people with hypertension should attach attention to their subjective estimates of the ease of sleep onset, sleep maintenance, total sleep time, early awakening, restlessness during the night, and anxiety, tension, or calmness when trying to sleep (Harvey, Kathleen, Whitaker, Damian, & Harvinder, 2008).
Under normal circumstances, the sleep habits of the elderly would undergo physiological changes, but some of the excessive changes in sleep habits were considered to be part of sleep disorders (Hoffman, 2003; Kryger, Monjan, Bliwise, & Ancoli-Israel, 2004; Rajput & Bromley, 1999). Previous studies have found that most people suffer from sleep disturbance as a fact of the aging process (Fermina & Revathi, 2017), which was mainly manifested by awakening at night, cough, a feeling of breathlessness/cold/hot/pain. It was because aging would weaken people’s homeostatic sleep drive by age 50, and the amplitude of the circadian rhythm would decline with aging (Smith et al., 2018). Related studies found that 73% of pulmonary hypertensive patients experienced poor sleep quality associated with sleep disturbance (Batal, Khatib, Bair, Aboussouan, & Minai, 2011; Minai, Malik, Foldvary, Bair, & Golish, 2008). Sleep disturbance can be caused by insomnia and restless leg syndrome, and the symptoms interfere with people’s lives and negatively affect HRQoL (MaturaMcdonough & Carroll, 2012). Thus, the nondipping pattern through a disruption of the circadian rhythm as well as the increase in the frequency of awakening would lead to a decrease in the deep sleep period, and sleep deficiencies made people inactive (Erden et al., 2010).
Optimal sleep depends on individuals' sleep requirement and circadian rhythm, once one or both of the critical elements are disrupted, daytime dysfunction and non–restorative sleep may occur (Gamaldo, Chung, Yu, & Salas, 2014). It’s not difficult to find that daytime dysfunction is a negative result of poor sleep quality at night, and it would lead to a reduced sense of life quality in this study. In general, feeling tired when waking up in the morning is one of the main manifestations of daytime dysfunction. Separate studies have proved that daytime dysfunction caused by poor sleep, would pose a negative impact on life quality, thus worsening symptoms of the underlying disease like hypertension (NasirShahid & Shabbir, 2015; Parish & M., 2009).
What could be underlined was that we assessed the association between PSQI and HRQoL by calculating PSQI components as well as the global score. Although this study cannot explain the causal relationship between sleep quality and life quality in hypertensive patients, the correlation analysis shows that the sleep quality of hypertensive patients is related to the quality of life.