Daytime napping, sleep duration and serum C reactive protein: a population-based cohort study

Abstract

Objectives To explore whether daytime napping and sleep duration are linked to serum C reactive protein (CRP), a pro-inflammatory marker, in an older aged British population. Design Cross-sectional study. Setting European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study. Participants A total of 5018 men and women aged 48–92 years reported their sleep habits and had serum CRP levels measured. Outcome and measures CRP was measured (mg/L) during 2006–2011 in fresh blood samples using high-sensitivity methods. Participants reported napping habits during 2002–2004, and reported sleep quantity during 2006–2007. Multivariable linear regression models were used to examine the association between napping and log-transformed CRP, and geometric mean CRP levels were calculated. Results After adjustment for age and sex, those who reported napping had 10% higher CRP levels compared with those not napping. The association was attenuated but remained borderline significant (β=0.05 (95% CI 0.00 to 0.10)) after further adjustment for social class, education, marital status, body mass index, physical activity, smoking, alcohol intake, self-reported health, pre-existing diseases, systolic blood pressure, hypnotic drug use, depression and in women-only hormone replacement therapy use. The geometric means (95% CI) of CRP levels were 2.38 (2.29 to 2.47) mg/L and 2.26 (2.21 to 2.32) mg/L for those who reported napping and no napping, respectively. A U-shaped association was observed between time spent in bed at night and CRP levels, and nighttime sleep duration was not associated with serum CRP levels. The association between napping and CRP was stronger for older participants, and among extremes of time spent in bed at night. Conclusions Daytime napping was associated with increased CRP levels in an older aged British population. Further studies are needed to determine whether daytime napping is a cause for systemic inflammation, or if it is a symptom or consequence of underlying health problems.

The interactive effects of nocturnal sleep and daytime naps in relation to serum C-reactive protein

“…Participants were asked how often they napped in the previous 7 days: “never to a few times”( few nap),“almost every day”( most nap), and “every day”( all nap). Consistent with a previous large cohort nap investigation 10 , CRP collection was performed ~6 yrs after nap data collection. Individuals reported typical sleep and rise time for weekday and weekend overnight sleep.…”

“…We included covariates previously linked with CRP alterations 4,10,16 . Sex, age, race/ethnicity, daily physical activity, socioeconomic status, depression status, snoring, and clinical symptoms of illness were self-reported, while BMI, systolic blood pressure, and CRP were not.…”

“…For example, CRP increases with both experimental sleep deprivation 6 and poor self-rated sleep quality 4,7 in a dose-dependent manner. Contrarily, several investigations have linked long sleep (≥9 hrs/night) with higher CRP in individuals with Obstructive Sleep Apnea and type 2 diabetes 8–10 . Others, however, have found no connection between sleep duration, quality, and CRP levels 11,12 .…”

“…For example, a large cohort investigation compared two groups of older adults (M age = 69.5 yrs): those who reported napping at least once per week and those who did not nap (i.e., not differentiating between those with frequent and infrequent nap incidence) 10 . Self-reported nappers had increased CRP, and the authors suggested that frequent naps may actively elevate CRP, possibly via enhanced blood pressure upon waking.…”

Occupational stress and work efficiency of nursing staff engaged in rotating shift work

“…Duration of sleep was self-recorded by the participants (Leng et al 2014) using a sleep log in which they recorded the total hours of sleep time they had between the first and second shifts of each part of a shift cycle (that is, during morning shifts, afternoon shifts, night shifts and days off -although results from days off are not reported in this article).…”