Low life purpose and high hostility are related to an attenuated decline in nocturnal blood pressure.

The majority of individuals exhibit a diurnal pattern of blood pressure (BP) variation, in which nighttime BP decreases relative to daytime BP. Individuals who show less of a nighttime decline in BP are at increased risk for cardiovascular events (Ohkubo et al., 2002; Staessen et al., 1999; Verdecchia, Angeli, Borgioni, Gattobigio, & Reboldi, 2007), declining renal function (Davidson, Hix, Vidt, & Brotman, 2006), and mortality (Fagard et al., 2008). The prognostic value of night-to-day BP ratios for health outcomes is independent of, and at times stronger than, daytime BP levels (Davidson et al., 2006; Fagard et al., 2008; Ohkubo et al., 2002; Staessen et al., 1999). Thus, identification of factors that disrupt the normal diurnal pattern of BP may help to inform strategies for the prevention and treatment of cardiovascular disease and related disorders. Negative emotions may be among the factors that have a detrimental effect on night-day BP ratios, as they may occur in conjunction with cognitive rumination and impaired recovery of the sympathetic nervous system (Pieper & Brosschot, 2005). On the other hand, positive traits and emotions may facilitate a healthier rhythm due to an increased ability to cope with life stressors or remain optimistic in the face of challenges. Indeed, available data offer support for associations between individual differences in psychological attributes and diurnal BP rhythms. Negative emotions, including depression, anxiety, and hostility and anger, have been related to an attenuated decline in nighttime BP (Kario, Schwartz, Davidson, & Pickering, 2001; Steffen, McNeilly, Anderson, & Sherwood, 2003; Thomas, Nelesen, & Dimsdale, 2004), although not all studies have found significant relationships (Ituarte, Kamarck, Thompson, & Bacanu, 1999; Linden, Klassen, & Phillips, 2008). Preliminary evidence for an association between positive psychological characteristics and a healthy diurnal BP rhythm comes from the finding that daily mood ratings of pleasantness and happiness were related to lower absolute levels of diastolic BP during the night in healthy young adults (Shapiro, Jamner, & Goldstein, 1997). Studies have also shown that positive emotions and traits are associated with lower resting BP and faster BP recovery following stressful tasks (Ostir, Berges, Markides, & Ottenbacher, 2006; Steptoe, Gibson, Hamer, & Wardle, 2007). However, the relationship between positive attributes and night-day BP ratios has not been evaluated directly. As positive and negative emotions and attitudes are not simply opposite ends of a single continuum, it is reasonable to examine both of these aspects separately in relation to BP rhythms. One potential pathway linking psychological factors to night-day BP ratios is disturbed sleep. Ryff, Singer, and Love (2004) observed an inverse association between purpose in life and movement throughout the night in older women, and a recent study reported that both positive affect and eudaimonic well-being were related to better self-reported sleep quality (Steptoe, O'Donnell, Marmot, & Wardle, 2008). On the contrary, elevated negative affect is related to longer sleep latency, increased fragmentation throughout the night, and a decreased percentage of time spent in slow-wave sleep (Grano, Vahtera, Virtanen, Keltikangas-Jarvinen, Kivimaki, 2008; Paudel et al., 2008; Spira, Stone, Beaudreau, Ancoli-Israel, & Yaffe, 2009; Thase, Fasiczka, Berman, Simons, & Reynolds, 1998). The sleep of individuals with higher nighttime BP is characterized by similar disturbances in sleep latency, fragmentation, and architecture (Loredo, Nelesen, Ancoli-Israel, & Dimsdale, 2004; Mansoor, 2002; Matthews et al., 2008). Moreover, sleep apnea is associated with a blunted decline in nocturnal BP in both cross-sectional and prospective studies (Hla, Young, Finn, Peppard, Szklo-Coxe, & Stubbs, 2008; Suzuki, Guilleminault, Ostuka, Shiomi, 1996). Given these associations, it is possible that sleep may partially account for the reported links between psychological attributes and diurnal BP rhythms. However, most previous studies either have not assessed sleep or have assessed sleep with self-report measures of sleep quality. Other dimensions – such as sleep continuity, architecture, or disordered breathing – can be measured with techniques such as actigraphy or polysomnography, and could plausibly affect BP rhythms as well. Whether or not these sleep parameters act as mediators linking psychological attributes with BP rhythms is unknown. We have previously reported in the present sample that higher sleep-wake BP ratios are associated with poorer sleep continuity and increased Stage 1 sleep (Matthews et al., 2008). Here, we investigate the hypotheses that negative (depression, anxiety, and hostility) and positive (optimism and life purpose) psychological attributes are associated with sleep-wake BP ratios and evaluate whether such associations are independent of sleep continuity, architecture, and sleep-disordered breathing.