Graduation Year

2016

Document Type

Thesis

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Epidemiology and Biostatistics

Major Professor

Kathleen O'Rourke, Ph.D.

Committee Member

Skai Schwartz, Ph.D.

Committee Member

William Sappenfield, MD, MPH

Committee Member

Wei Wang, Ph.D.

Committee Member

Marisa Couluris, DO

Keywords

Sleep duration, asthma, adolescents, inflammation, longitudinal, young adults

Abstract

This dissertation includes three studies that examined the impact of inadequate sleep duration in adolescents and young adults on asthma and systemic inflammation. We used data from the Florida Youth Risk Behavior Survey (YRBS), years 2009-2013, and from the National Longitudinal Study of Adolescent to Adult Health (Add health), which was conducted between 1994 and 2008.

The first study used data from 16,738 high school students participating in the Florida YRBS. We examined the cross-sectional association between sleep duration and asthma, and the interactive effects of sleep duration and BMI. We found that short and long sleep durations were associated with increased odds of current asthma. Compared with 7-8 hours of sleep per night, sleeping for(95% CI) of 1.22 (1.07, 1.40), while sleeping for ≥ 9 hours had and OR of 1.31 (1.06, 1.63). We found a significant effect modification by BMI, with the associations between sleep duration and asthma mostly limited to overweight adolescents. Compared with normal weight students who sleep for 7-8 hours per night, those who are overweight and sleep for≥ 9 hours have approximately twice the odds of having current asthma [OR= 1.75 (1.45, 2.11), and OR=2.00 (1.32, 3.02) respectively]. No significant associations were found in normal-weight adolescents.

The second study used data from 12,633 adolescents (age 13-19) participating in the National Longitudinal Study of Adolescent to Adult Health (Add health), and followed through 4 waves of interviews through their young adulthood (age 24-32). We constructed trajectories of sleep duration through 4 waves of data for participants without asthma at wave I (n=11,016), and examined the association between sleep duration and the risk of asthma by young adulthood. Similarly, we constructed trajectories of sleep duration for participants with asthma at wave I (n=1,395) through 3 waves of data, and examined the association between sleep duration and persistence of asthma into young adulthood. Sleep trajectories in non-asthmatic participants showed that 13.8% of them had persistent short sleep duration, while 80.7% had adequate sleep durations from adolescence though young adulthood. Those with consistently short sleep had 1.59 times the risk of new onset asthma by age 32 (95% CI 1.12, 2.26), compared with consistently adequate sleepers. Among adolescents with asthma, 10.2% had consistently short sleep through age 24, while 81.2% had adequate sleep. Short sleepers were 2.35 times more likely than adequate sleepers to have their asthma symptoms persist into young adulthood (95% CI 1.12, 4.96).

The third study used data from waves III and IV of the Add health study, and examined the association between sleep trajectories over a 6-year follow-up in young adulthood, and the risk of elevated high sensitivity C-reactive protein (hs-CRP), a marker of systemic inflammation. Short sleep trajectories were associated with a significant increase in log-transformed hs-CRP (coefficient=0.11, p-value 0.03), and with a significant increase in the odds of having hs-CRP levels >3 mg/dl (OR=1.85, 95% CI 1.29, 2.67). The association was modified by sex, with the association between short sleep duration and hs-CRP limited to males. In males, both the continuous (coefficient 0.117, p-value=0.0362) and the categorized hs-CRP (OR= 2.21, 95% CI 1.48, 3.30) were significantly increased with short sleep durations, while no significant associations were seen in females with short sleep durations. By contrast, there was a significant increase in log hs-CRP in females with long sleep durations (coefficient=0.232, p-value=0.0296), and a non-significant increase in the odds of having hs-CRP levels greater than 3 mg/dl (OR=1.48, 95% CI 0.75, 2.93), while there were no associations with long sleep duration in males.

The results of this dissertation research point to the detrimental effects of sleep loss on the bodies of adolescents and young adults. We found sleep loss to be associated with the incidence of asthma and its persistence, in addition to heightened systemic inflammation, which is a likely pathway that links sleep duration with the above outcomes. Our findings indicate that males are more susceptible to the effect of insufficient sleep on the risk of heightened inflammation, while females are more susceptible to the effects of long sleep durations. Interestingly, adolescents in the more recent YRBS study had shorter sleep durations than those who participated in the earlier Add health study. The prevalence of sleeping less than 7 hours was 16.5% in the add health study (years 1994-1995), compared with 47.2% in the YRBS study (years 2009-2013), indicating a progressive decrease in the average sleep duration of adolescents.

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