LAUSR

Metabolic syndrome (MetS) in middle-aged adults increases a risk of cardiovascular disease in their older ages. The rest-activity rhythms disruptions have been linked to metabolic dysfunctions. However, there are limited data for the association between rest-activity rhythms and MetS in middle-aged. The purpose of this analysis was to compare rest-activity rhythms between midlife adults with MetS and those without MetS. This study was a secondary analysis of data from Midlife in the United States (MIDUS 2): Biomarker Project, 2004-2009 cohort. The rest-activity rhythms were described by four parameters: the mesor, the amplitude, the acrophase, and the goodness-of-fit (R2), generated from Cosinor analysis using Actiwatch activity monitor data. Metabolic syndrome was defined as having three or more the following traits: the waist circumference ≥85cm in women and ≥102cm in men, the triglyceride level ≥150mg/dL, the high-density lipoprotein < 50mg/dL in women and < 40mg/dL in men, the blood pressure ≥130/85 mmHg, the fasting blood sugar level ≥100mg/dL. Student T-test were conducted. The sample (N=302; mean age 54.7 years [range 34 – 83]; 55.3% female; 97.3% White; 72.8) consists of 60.9% of persons with MetS (n=184) and 39.1% of those without MetS (n=118). The MetS group was older and more likely to be male than the non-MetS group (all p<.05). The MetS group had statistically lower mesor (mean 221.7 vs. 246.1; p=.005) and amplitude (mean 183.1 vs. 207.9; p=.004) than the non-MetS group. R square (0.58 vs. 0.62; p=.004) was significantly lower in the MetS than the non-MetS group. However, acrophase was not associated with MetS. Midlife adults, those with MetS had lower levels of average activity and lower amplitude of rest-activity rhythms than those with non-MetS. The circadian rest-activity rhythms were significantly fragmented in those with MetS than with those non-MetS. Our findings suggest that the disrupted rest-activity rhythm could be a modifiable factor to manage MetS in midlife. Partially supported by the University of Iowa Institute for Clinical and Translational Science (NIH/ ACTS KL2TR002536) and University of Iowa Center for Advancing Multimorbidity Science (NIH/ NINR P20 NR018081). Contents are solely the responsibility of the authors.