Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2018 Apr 1.
Published in final edited form as: J Behav Med. 2016 Sep 3;40(2):360–365. doi: 10.1007/s10865-016-9792-0

Dispositional optimism and sleep quality: a test of mediating pathways

Bert N Uchino 1,✉, Matthew Cribbet 2, Robert G Kent de Grey 1, Sierra Cronan 1, Ryan Trettevik 1, Timothy W Smith 1
PMCID: PMC5334440  NIHMSID: NIHMS814713  PMID: 27592128

Abstract

Dispositional optimism has been related to beneficial influences on physical health outcomes. However, its links to global sleep quality and the psychological mediators responsible for such associations are less studied. This study thus examined if trait optimism predicted global sleep quality, and if measures of subjective well-being were statistical mediators of such links. A community sample of 175 participants (93 men, 82 women) completed measures of trait optimism, depression, and life satisfaction. Global sleep quality was assessed using the Pittsburgh Sleep Quality Index. Results indicated that trait optimism was a strong predictor of better PSQI global sleep quality. Moreover, this association was mediated by depression and life satisfaction in both single and multiple mediator models. These results highlight the importance of optimism for the restorative process of sleep, as well as the utility of multiple mediator models in testing distinct psychological pathways.

Keywords: Depression, Health, Life satisfaction, Optimism, Sleep

Introduction

Trait optimism represents the general expectation that good things will happen in the future (Carver & Scheier, 2014) and meta-analytic reviews have found it to predict better health across a number of outcomes (e.g., cardiovascular disease, DuBois et al., 2015; Rasmussen et al., 2009). Given existing epidemiological data, one might expect dispositional optimism to predict better sleep. Sleep plays an important role in biological restoration and repair (Hawkley & Cacioppo, 2004; Robles & Carroll, 2011) and emerging research has linked indicators of sleep to negative health outcomes (Cohen et al., 2009; Irwin, 2014; King et al., 2008). However, the optimism-global sleep quality link has been less studied so more research is needed in order to better characterize the scope of outcomes related to optimism.

At a broader theoretical level, there are good reasons to suspect that trait optimism would be related to better global sleep quality. Optimists engage in greater proactive coping which is an adaptive orientation for dealing with stressful upcoming events (Aspinwall & Taylor, 1997). Optimists also engage in positive self-regulatory behaviors when directly dealing with stress which has downstream benefits such as higher future work salaries (Nes Solberg et al., 2009; Segerstrom & Solberg Nes, 2006). More generally, optimists engage in approach coping strategies in comparison to avoidant coping strategies (Nes & Segerstrom, 2006). These beneficial proactive and self-regulatory coping strategies should result in better global sleep quality via higher subjective well-being. Consistent with this reasoning, preliminary evidence links optimism to key aspects of sleep, including both self-reported global sleep quality/insomnia symptoms (Sing & Wong, 2011; Lemola et al., 2013) and actigraphy-derived measures of sleep duration and sleep efficiency (Lemola et al., 2011). Moreover, experimental evidence suggests that self-reported optimism declines during sleep restriction and returns to baseline levels with recovery sleep (Haack & Mullington, 2005).

Although dispositional optimism is generally linked to better health outcomes, much less is known on potential psychological pathways responsible for such links (Rasmussen et al., 2009). Psychological processes related to subjective well-being are likely mediators and include both positive and negative affect/evaluative processes (Pavot & Diener, 2008). Of these, depression and life satisfaction are important indicators and have been strongly linked to trait optimism in a prior meta-analytic review (Alarcon et al. 2013). Although poor sleep is strongly associated with higher levels of depression (Irwin, 2014), no study to date appears to have examined both positive and negative indicators of subjective well-being as potential mediators.

The major aims of the present study were thus to examine the link between trait optimism and PSQI global sleep quality and model psychological pathways. Based on prior work, it was predicted that optimism would be related to better global sleep quality and that depression and life satisfaction will be statistical mediators. This study also examined the utility of modeling multiple mediators given most prior work has focused on single mediation models. It was hypothesized that a multiple mediator model would show a stronger mediator link given depression and life satisfaction are distinct measures of subjective well-being.

Methods

Participants and procedure

One hundred seventy-five relatively healthy community participants (93 men and 82 women) participated in this IRB approved study. The sample was middle-aged to older adults between 48 and 77 (Mage = 60.1, SD = 6.5). The median education level was college graduation and the median income was $40,000 or more per year. As part of the larger study focusing on psychosocial predictors of health, individuals with serious medical problems were excluded (e.g., cancer, see Uchino et al., 2012a). Eligible participants were scheduled for an appointment and provided informed consent. Participants completed a demographic questionnaire, the Life Orientation Test-Revised, Pittsburgh Sleep Quality Index, as well as The Center for Epidemiologic Studies Depression Scale and the Life Satisfaction Scale (see below). Participants were then debriefed and compensated. The authors have no conflicts of interest.

Measures

Life orientation test-revised (LOT-R)

The LOT-R is a 10-item scale which includes filler items and assesses dispositional optimism (Scheier et al., 1994). It has good psychometric properties and is distinguishable from other personality constructs (Scheier et al., 1994). The internal consistency of the scale in the present study was high (.83).

PSQI

The Pittsburgh Sleep Quality Index (PSQI) assesses sleep quality disturbances during the previous month (Buysse et al., 1989). The scale is comprised of 19 items which are used to derive a global PSQI score with higher scores indicating poorer sleep quality. This instrument has demonstrated good reliability and validity (Morin & Espie, 2003). The internal consistency of the global PSQI in the current study was .73.

CES-D

The Center for Epidemiologic Studies Depression Scale (CES-D) is a 20-item scale that assesses depressive symptoms. The Cronbach’s alpha was high in both patient and control samples (.90), with a 4 weeks test–retest correlation of .67 (Radloff, 1977). Importantly, the CES-D also has good sensitivity for detecting depressive symptoms (Lyness et al., 1997). The internal consistency of the CES-D in the current study was similarly high (.91). In all analyses, the item dealing with sleep problems was deleted to avoid overlap with the PSQI.

Satisfaction With Life Scale (SWLS)

The SWLS is a 5 item scale that measures general life satisfaction (Diener et al., 1985). The SWLS is characterized by high internal consistency (e.g., .89) and good test–retest reliability (e.g., 4 years test–retest reliability of .54, Pavot & Diener, 1993). The internal consistency of the scale in this study was high (.92).

Statistical analysis plan

A simultaneous regression analysis was used to test the hypothesized link between trait optimism and PSQI global sleep quality. Consistent with prior work, basic demographic factors were statistically controlled and included age, sex, income, and education as they have been linked to sleep patterns (Hall et al., 2008; Mezick et al., 2008). The proposed psychological mediators of depression and life satisfaction were first tested individually using bootstrapping (2000 resamples, Preacher & Hayes, 2004) given they are distinct constructs. The proposed mediators were then tested together to examine the utility of a multiple mediator model.

Results

Preliminary analyses

Replicating prior work, zero-order correlations showed that higher trait optimism was related to lower depression (r = −.57, p < .001) and higher life satisfaction (r = .61, p < .001). The zero-order correlation between trait optimism and sleep was also significant (r = −.45, p < .001). The mean global PSQI score for this sample was 6.15 (SD = 3.6, range 0–17) which is indicative of poor sleep quality (Buysse et al., 2008; Grandner et al., 2006).

Main analyses

As shown in Table 1, dispositional optimism was a significant predictor of sleep quality while statistically controlling for basic demographic factors. Consistent with the few studies in the area, higher trait optimism was associated with better PSQI global sleep quality [b = −1.88, 95 % CI (−2.52, −1.24), β = −.41, p < .0001]. In fact, trait optimism was a significant predictor of each component of global sleep quality (p’s < .05) except for sleep efficiency (p < .10). Subgroup analyses examining normal (PSQI < 5, n = 63) and poor sleepers (PSQI ≥ 5, n = 112) found that trait optimism significantly predicted better global sleep quality only in the poor sleep group (p < .001) although analyses of normal sleepers was characterized by less statistical power and a more restricted range.

Table 1.

Results of simultaneous regression analyses predicting sleep quality (n = 175)

Variable b 95 % CI β t p
Age −.05 (−.13, .03) −.09 1.22 .22
Sex female .69 (−.27, 1.66) .10 1.42 .16
Income −.16 (.−.39, .07) −.10 1.40 .16
Education −.13 (−.49, .23) −.05 .70 .48
Optimism −1.88 (−.2.52, −1.25) −.41 5.82 .0001
Open in a new tab

Overall model R2 = .23, adjusted R2 = .20

Bootstrap mediational models were next tested with depression and life satisfaction in single and multiple mediator models. The bias corrected bootstrap analysis indicated that the indirect effect of trait optimism on better sleep quality via depression was significant [a × b = −.73, 95 % CI (−1.25, −.31)]. The bias corrected bootstrap analyses examining life satisfaction also showed a significant mediating influence on the optimism—sleep quality link [a × b = −.84, 95 % CI (−1.47, −.41)]. However, as shown in Fig. 1, examination of depression and life satisfaction in a multiple mediator model produced the strongest indirect effect [a × b = −1.06, 95 % CI (−1.75, −.54)] suggesting that they are both important mediators of such links.

Fig. 1.

Fig. 1

Open in a new tab

Multiple mediator model linking trait optimism to global sleep quality

Discussion

The present study sought to provide evidence for a link between dispositional optimism and PSQI global sleep quality as well as the psychological mediators potentially responsible for such links. Consistent with a small body of research, dispositional optimism was related to better global sleep quality. In addition, this link was statistically mediated by depression and life satisfaction. These results are consistent with broader epidemiological research showing that trait optimism is related to better health outcomes across a number of biological systems and disease conditions (DuBois et al., 2015; Rasmussen et al., 2009). In addition, these data highlight the importance of subjective well-being measures as psychological mediators.

The first main goal of the study was to provide additional data on the link between trait optimism and PSQI global sleep quality. Consistent with predictions, optimism was related to better global sleep quality. These data are important as sleep has emerged as an important restorative process that is related to health outcomes (Hawkley & Cacioppo, 2004; Irwin, 2014; Robles & Carroll, 2011). For instance, the CARDIA study found that longer sleep was related to less coronary artery calcification (King et al., 2008). This study, among others (Lau et al., 2015; Lemola et al., 2013), adds to the growing list of health-relevant outcomes associated with dispositional optimism which can potentially explain epidemiological links to more downstream health conditions.

A second major aim of this study was to test measures of subjective well-being as statistical mediators. The link between trait optimism and PSQI global sleep quality was mediated by depression and life satisfaction, with stronger influences in a multiple mediator model which included both. These data highlight the importance of subjective well-being as pathways linking trait optimism to health outcomes. More research will be needed to test whether subjective well-being is an important mediator for other health outcomes associated with dispositional optimism such as immune-mediated inflammation. Future epidemiological work might also benefit from examining more complex models of mediation informed by this work. For instance, both subjective well-being and global sleep quality could be included in a process mediational model predicting distal health outcomes (Judd & Kenny, 1981).

These data are also important because much of the prior work on psychosocial risk factors and health examines single mediator models. It has been argued that such models are unlikely to reveal strong evidence for mediators given the likely small effect size associated with any one pathway (Uchino et al. 2012b). Testing multiple mediators can thus better inform theoretical frameworks by highlighting more complex pathways.

There are several important limitations of this work. These data are cross-sectional so longitudinal designs will be needed in future studies to strengthen inferences. To this point, it is important to note that some research indicates that sleep problems might influence mood states and perceptions of optimism. For instance, participants who were randomized to 4 h of sleep (compared to 8 h) for 12 consecutive days showed progressive declines in state levels of optimism/sociability (Haack & Mullington, 2005). Similarly, a longitudinal study found evidence for both associations as trait optimism was related to poorer sleep over time, and poor sleep was related to lower dispositional optimism over time (Lau et al., 2015). Finally, although subjective sleep quality has been linked to objective sleep indicators, this study did not collect such measures (e.g., polysomnography) which might provide converging evidence for such links.

These limitations notwithstanding, these data are among the first showing mediation of the link between trait optimism and global sleep quality using a multiple mediator model. It is important to highlight that facets of sleep are linked to negative health outcomes (Irwin, 2014) and thus underscores the potential importance of developing interventions that could augment perceptions of optimism. Preliminary attempts to foster greater optimism include imagery and writing manipulations (Peters et al., 2013; Sergeant & Mongrain, 2014). However, future work will be needed to demonstrate that such interventions also alter health related outcomes of relevance to the present study and larger literature. Such work could play a critical role in helping researchers better understand the links between optimism and health.

Acknowledgments

Support for this research was generously provided by Grant Number R21 AG029239 from the National Institute on Aging.

Footnotes

Conflict of interest Bert N. Uchino, Matthew Cribbet, Robert G. Kent de Grey, Sierra Cronan, Ryan Trettevik, and Timothy W. Smith declares that they have no conflict of interest.

Compliance with ethical standards

Human and animal rights and Informed consent All procedures followed were in accordance with ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000. Informed consent was obtained from all patients for being included in the study.

References

  1. Alarcon GM, Bowling NA, Khazon S. Great expectations: A meta-analytic examination of optimism and hope. Personality and Individual Differences. 2013;54:821–827. doi: 10.1016/j.paid.2012.12.004. [DOI] [Google Scholar]
  2. Aspinwall LG, Taylor SE. A stitch in time: Self-regulation and proactive coping. Psychological Bulletin. 1997;121:417–436. doi: 10.1037/0033-2909.121.3.417. [DOI] [PubMed] [Google Scholar]
  3. Buysse DJ, Hall ML, Strollo PJ, Kamarck TW, Owens J, Lee L, et al. Relationships between the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and clinical/polysomnographic measures in a community sample. Journal of Clinical Sleep Medicine. 2008;4:563–571. [PMC free article] [PubMed] [Google Scholar]
  4. Buysse DJ, Reynolds CF, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh Sleep Quality Index: A new instrument for psychiatric practice and research. Psychiatry Research. 1989;28:193–213. doi: 10.1016/0165-1781(89)90047-4. [DOI] [PubMed] [Google Scholar]
  5. Carver CS, Scheier MF. Dispositional optimism. Trends in Cognitive Sciences. 2014;18:293–299. doi: 10.1016/j.tics.2014.02.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Archives of Internal Medicine. 2009;169:62–67. doi: 10.1001/archinternmed.2008.505. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Diener E, Emmons RA, Larsen RJ, Griffin S. The Satisfaction With Life Scale. Journal of Personality Assessment. 1985 doi: 10.1207/s15327752jpa4901_13. [DOI] [PubMed] [Google Scholar]
  8. DuBois CM, Lopez OV, Beale EE, Healy BC, Boehm JK, Huffman JC. Relationships between positive psychological constructs and health outcomes in patients with cardiovascular disease: A systematic review. International Journal of Cardiology. 2015;195:265–280. doi: 10.1016/j.ijcard.2015.05.121. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Grandner MA, Kripke DF, Yoon IY, Youngstedt SD. Criterion validity of the Pittsburgh Sleep Quality Index: Investigation in a non-clinical sample. Sleep and Biological Rhythms. 2006;4:129–136. doi: 10.1111/j.1479-8425.2006.00207.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Haack M, Mullington JM. Sustained sleep restriction reduces emotional and physical well-being. Pain. 2005;119:56–64. doi: 10.1016/j.pain.2005.09.011. [DOI] [PubMed] [Google Scholar]
  11. Hall M, Buysse DJ, Nofzinger EA, Reynolds CF, Thompson W, Mazumdar S, et al. Financial strain is a significant correlate of sleep continuity disturbances in late-life. Biological Psychology. 2008;77:217–222. doi: 10.1016/j.biopsycho.2007.10.012. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hawkley LC, Cacioppo JT. Stress and the aging immune system. Brain, Behavior, and Immunity. 2004;18:114–119. doi: 10.1016/j.bbi.2003.09.005. [DOI] [PubMed] [Google Scholar]
  13. Irwin MR. Why sleep is important for health: A psychoneuroimmunology perspective. Annual Review of Psychology. 2014 doi: 10.1146/annurev-psych-010213-115205. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Judd CM, Kenny DA. Process analysis estimating mediation in treatment evaluations. Evaluation Review. 1981;5:602–619. doi: 10.1017/CBO9781107415324.004. [DOI] [Google Scholar]
  15. King CR, Knutson KL, Rathouz PJ, Sidney S, Liu K, Lauderdale DS. Short sleep duration and incident coronary artery calcification. JAMA: The Journal of the American Medical Association. 2008;300:2859–2866. doi: 10.1001/jama.2008.867. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lau EYY, Hui CH, Cheung SF, Lam J. Bidirectional relationship between sleep and optimism with depressive mood as a mediator: A longitudinal study of Chinese working adults. Journal of Psychosomatic Research. 2015;79:428–434. doi: 10.1016/j.jpsychores.2015.09.010. [DOI] [PubMed] [Google Scholar]
  17. Lemola S, Räikkönen K, Gomez V, Allemand M. Optimism and self-esteem are related to sleep. Results from a large community-based sample. International Journal of Behavioral Medicine. 2013;20:567–571. doi: 10.1007/s12529-012-9272-z. [DOI] [PubMed] [Google Scholar]
  18. Lemola S, Räikkönen K, Scheier MF, Matthews KA, Pesonen AK, Heinonen K, et al. Sleep quantity, quality and optimism in children. Journal of Sleep Research. 2011;20:12–20. doi: 10.1111/j.1365-2869.2010.00856.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Lyness JM, Noel TK, Cox C, King DA, Conwell Y, Caine ED. Screening for depression in elderly primary care patients: A comparison of the Center for Epidemiologic Studies—Depression Scale and the Geriatric Depression Scale. Archives of Internal Medicinerchives of Internal Medicine. 1997;157:449–454. [PubMed] [Google Scholar]
  20. Mezick EJ, Matthews KA, Hall M, Strollo PJ, Buysse DJ, Kamarck TW, et al. Influence of race and socioeconomic status on sleep: Pittsburgh SleepSCORE project. Psychosomatic Medicine. 2008;70:410–416. doi: 10.1097/PSY.0b013e31816fdf21. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Morin CM, Espie CA. Insomnia: A clinician’s guide to assessment and treatment. Vol. 1. New York: Springer; 2003. [Google Scholar]
  22. Nes LS, Segerstrom SC. Dispositional optimism and coping: A meta-analytic review. Personality and Social Psychology Review. 2006;10:235–251. doi: 10.1207/s15327957pspr1003_3. [DOI] [PubMed] [Google Scholar]
  23. Nes Solberg L, Evans DR, Segerstrom SC. Optimism and college retention: Mediation by motivation. Journal of Applied Social Psychology. 2009;39:1887–1912. [Google Scholar]
  24. Pavot W, Diener E. Review of the satisfaction with life scale. Psychological Assessment. 1993;5:164–172. doi: 10.1037/1040-3590.5.2.164. [DOI] [Google Scholar]
  25. Pavot W, Diener E. The satisfaction with life scale and the emerging construct of life satisfaction. Journal of Positive Psychology. 2008;3:137–152. [Google Scholar]
  26. Peters ML, Meevissen YMC, Hanssen MM. Specificity of the best possible self intervention for increasing optimism: Comparison with a gratitude intervention. Terapia Psycológica. 2013;31:93–100. doi: 10.4067/S0718-48082013000100009. [DOI] [Google Scholar]
  27. Preacher KJ, Hayes AF. SPSS and SAS procedures for estimating indirect effects in simple mediation models. Behavior Research Methods, Instruments, and Computers. 2004;36:717–731. doi: 10.3758/BF03206553. [DOI] [PubMed] [Google Scholar]
  28. Radloff LS. The CES-D Scale: A self-report depression scale for research in the general population. Applied Psychological Measurement. 1977;1:385–401. doi: 10.1177/014662167700100306. [DOI] [Google Scholar]
  29. Rasmussen HN, Scheier MF, Greenhouse JB. Optimism and physical health: A meta-analytic review. Annals of Behavioral Medicine. 2009;37:239–256. doi: 10.1007/s12160-009-9111-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Robles TF, Carroll JE. Restorative biological processes and health. Social and Personality Psychology Compass. 2011;5:518–537. doi: 10.1111/j.1751-9004.2011.00368.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Scheier MF, Carver CS, Bridges MW. Distinguishing optimism from neuroticism (and trait anxiety, self-mastery, and self-esteem): A reevaluation of the life orientation test. Journal of Personality and Social Psychology. 1994;67:1063–1078. doi: 10.1037/0022-3514.67.6.1063. [DOI] [PubMed] [Google Scholar]
  32. Segerstrom SC, Solberg Nes L. When goals conflict but people prosper: The case of dispositional optimism. Journal of Research in Personality. 2006;40:675–693. doi: 10.1016/j.jrp.2005.08.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Sergeant S, Mongrain M. An online optimism intervention reduces depression in pessimistic individuals. Journal of Consulting and Clinical Psychology. 2014;82:263–274. doi: 10.1037/a0035536. [DOI] [PubMed] [Google Scholar]
  34. Sing CY, Wong WS. The effect of optimism on depression: The mediating and moderating role of insomnia. Journal of Health Psychology. 2011;16:1251–1258. doi: 10.1177/1359105311407366. [DOI] [PubMed] [Google Scholar]
  35. Uchino BN, Bowen K, Carlisle M, Birmingham W. Psychological pathways linking social support to health outcomes: A visit with the “ghosts” of research past, present, and future. Social Science and Medicine. 2012a;74:949–957. doi: 10.1016/j.socscimed.2011.11.023. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Uchino BN, Cawthon RM, Smith TW, Light KC, McKenzie J, Carlisle M, et al. Social relationships and health: Is feeling positive, negative, or both (ambivalent) about your social ties related to telomeres? Health Psychology. 2012b;31:789–796. doi: 10.1037/a0026836. [DOI] [PMC free article] [PubMed] [Google Scholar]

RESOURCES