Extreme sleep durations and increased C-reactive protein: effects of sex and ethnoracial group

Abstract

Study objectives: We hypothesize that extremes of sleep duration are associated with elevated C-reactive protein (CRP), a pro-inflammatory marker for cardiovascular disease risk.

Design: Cross-sectional.

Setting: Population-based research.

Participants: Nationally representative sample of 2007-2008 National Health and Nutrition Examination Survey participants (n = 5,587 adults).

Interventions: None.

Measurements and results: Associations between CRP and self-reported total sleep time (TST) were examined. Explanatory models considered contributions of sex, age, race/ethnicity, body mass index (BMI), and BMI squared (BMI2). Models also explored the role of insomnia symptoms, sleep apnea, active medical illness, and antidiabetic/antihypertensive treatment. Differential patterns among race/ethnicity groups were examined using interactions and stratified analyses. Nonlinear relationships between CRP and TST were assessed using polynomial and multinomial regression models (< 5, 5, 6, 7, 8, 9, and > 9 h). Linear and squared terms were significant in all models in the complete sample, with notable differences by sex and ethnoracial group. Overall, in models adjusted for sociodemographics and BMI, different patterns were observed for non-Hispanic white (elevated CRP for < 5 h and > 9 h), black/African-American (elevated CRP for < 5 h and 8 h), Hispanic/Latino (elevated CRP for > 9 h), and Asian/ Other (higher in 9 and > 9 h and lower in 5 h and 6 h) groups. Ethnoracial groups also demonstrated patterning by sex.

Conclusion: In a representative sample of American adults, elevated CRP was associated with extreme sleep durations. Sex, race/ethnicity, sleep disorders, and medical comorbidity influenced these associations. Differences in CRP along these dimensions should be considered in future research on sleep related disparities influencing cardiometabolic disease risk.

Keywords: C-reactive protein; cardiovascular disease; epidemiology; inflammation; sleep duration.

Figure 1

Nonlinear relationship between sleep duration and mg/dL of C-reactive protein (CRP), represented in untransformed values for the complete sample (A), men alone (B), and women alone (C). Unadjusted figures represent Model 1. Adjusted figures represent Model 3, which includes age, sex, race/ethnicity, body mass index (BMI), body mass index squared (BMI), insomnia diagnosis, sleep apnea diagnosis, difficulty falling asleep, and snorting/gasping during sleep. A significant U shape to the distribution was found for Model 1 and Model 3 for the complete sample and for men, and a U shape was found for Model 1 but not Model 3 in women. Note that the U shape was significant for the complete sample, even if there was no elevation in the shortest sleep duration category. Asterisks (*) represent P < 0.05 difference from 7 h. Error bars = SEM.

Figure 2

Stratified results of sleep duration × race/ethnicity interactions for C-reactive protein (CRP). (A) Results for Model 2 (which includes age, sex, body mass index [BMI] and BMI) are displayed for the complete sample (interaction P = 0.003), men (interaction P < 0.001), and women (interaction P < 0.001). (B) Results for Model 3 are presented for the complete sample (interaction P = 0.003), men (interaction P < 0.001), women (interaction P < 0.001). *P < 0.05 relative to 7 h. Error bars = SEM.