Robust Circadian Rhythm Associated With Lower Cardiometabolic Risk

Some cardiometabolic risk factors may be associated with circadian rhythm parameters and physical activity, according to study results published in Obesity.

Researchers conducted a substudy of a multicenter, randomized controlled trial to determine post hoc associations among circadian rhythm parameters, physical activity, and cardiometabolic risk factors in adults with obesity and prediabetes after 3 years of weight loss maintenance. In the original study, no differences were observed among the 4 original intervention groups. Additional criteria were added to exclude participants with shift work and sleep disorders.

Participants (N=105; mean [SD] age, 56.6 [10] years; body mass index [BMI], 28.2 [4.0] kg/m²) wore a sleep accelerometer to quantify physical activity and sleep duration during all interventions. Circadian rhythm parameters were measured by monitoring wrist temperature continuously during the study. Although this parameter does not directly measure circadian rhythm, it was used as a surrogate due to its association with the timing of light exposure and amplitude of melatonin excretion.

Researchers pooled the data and used paired sample t tests to evaluate the differences in the participant characteristics and circadian rhythm parameters between 2 conditions: free-living and a respiration chamber. A total of 30 participants underwent both conditions.

Circadian rhythm parameters were significantly different between the 2 groups. The 48 hour respiration chamber period of time showed a more robust circadian rhythm even after controlling for fixed times for awakening and sleeping.

The cardiometabolic risk factors measured included systolic blood pressure, diastolic blood pressure, plasma high-density lipoprotein cholesterol (HDL-C), BMI, homeostatic model assessment of insulin resistance (HOMA-IR), heart rate, plasma low-density lipoprotein cholesterol (LDL-C), triacylglycerol, and remnant cholesterol.

There were no statistically significant differences between systolic blood pressure, diastolic blood pressure, plasma HDL-C, BMP, and HOMA-IR in the 2 study conditions. These factors were statistically related to each other. Heart rate and plasma LDL-C concentrations were lower and remnant cholesterol and triacylglycerol were lower.

Limitations of the study include a lack of generalizability to individuals who do not have obesity or prediabetes.

The study authors conclude, “In adults with obesity and prediabetes, parameters indicating a robust circadian rhythm were, independently of PA, associated with lower cardiometabolic risk and CRP.”