Date of Award

2016

Document Type

Open Access Dissertation

Department

Epidemiology and Biostatistics

Sub-Department

The Norman J. Arnold School of Public Health

First Advisor

James Burch

Abstract

Background: Chronotype, social jetlag, poor sleep, proinflammatory diet, and low physical activity have been associated with increased risk of chronic diseases: obesity, diabetes, cardiovascular disease, depression and cancer. Yet the relationships between these factors have not been extensively investigated in prospective studies.

Methods: Two studies were conducted. The first study followed 390 healthy men and women ages 21-35 for two years. Social jetlag [SJL] and sleep measures (total sleep time [TST], sleep onset latency [SOL], wake after sleep onset [WASO]), sleep efficiency [SE]), were derived from physical activity personal (armband) monitoring. The participants wore the armband for 4-10 days at 6-month intervals (1,431 observations). Temporal consistency of repeated sleep measures was analyzed using generalized linear mixed models (GLMM). Repeated measures latent class analyses (RMLCA) identified subgroups among participants with adequate or inadequate sleep characteristics over time. Relationships between chronotype, absolute SJL, sleep measures and anthropometric measures (Body Mass Index [BMI], Percent Body Fat [%BF], Waist-to-Hip Ratio [WHR], Waist-to-Height Ratio [WHtR], Systolic Blood Pressure [SBP] and Diastolic Blood Pressure [DBP], Total Mood Disturbance score [TMD], and Perceived Stress Score [PSS]) were analyzed using GLMM for repeated measures. Stratification by latent chronotype group was used to study effect modification.

The second study examined association between energy-density Dietary Inflammatory Index (e-DII) and incident PrCA among 40,161 men ages 45-69 at recruitment (2002-2003) and followed for a mean of 9.7 years. The e-DII was calculated from a food frequency questionnaire (FFQ) at baseline and categorized into quartiles. Incident PrCA cases were ascertained via linkage with cancer registry and categorized into three groups: high-risk, intermediate and low-risk. Accelerated failure time models were fit to model time-to-development of incident PrCA. Cox proportional hazards models were used to calculate hazard ratios (HR) and 95% confidence intervals (95% CI) of high- and intermediate risk PrCA. In all analyses, the lowest quartile of e-DII representing a more anti-inflammatory diet was used as the referent group.

Results: Minor temporary changes were observed only for SJL, chronotype and TST. The RMLCA identified two groups of absolute SJL: low (mean±SE: 0.8±0.6 h, 58%) and high (1.4±0.8, 42%); the latter were employed and had an evening chronotype. Subgroups with disrupted sleep tended to be male, African American, have a lower income, and an evening chronotype relative to those with normal sleep. Chronotype and absolute SJL were not associated with anthropometric characteristics. TST <6 >h, SE

Time-to-development of incident total PrCA did not differ by quartile of e-DII; although, among Whites, it was shorter relative to other races (AFQ4 vs.Q1=1.16; 95%CI:1.01-1.34). The hazard Ratio (HR) for high-risk PrCA was increased by 36% in the third quartile of the e-DII (95%CI:1.04-1.76); no increased risk was observed in the fourth quartile. The HR for high-risk PrCA was the highest among Blacks (HRQ3 vs.Q1=3.77; 95%CI:1.29-11.06). The e-DII was not associated with intermediate- or low-risk PrCA incidence.

Conclusions: Sleep disruption among young adults remained persistent during two years. Chronotype modified the association between disrupted sleep, obesity and elevated blood pressure. Pro-inflammatory diet increased risk of high-risk PrCA especially among Blacks.

Available for download on Tuesday, December 12, 2017

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