Timing of objectively-collected physical activity in relation to body weight and metabolic health in sedentary older people: a cross-sectional and prospective analysis.

BACKGROUND: Little is known about the impact of timing as opposed to frequency and intensity of daily physical activity on metabolic health. Therefore, we assessed the association between accelerometery-based daily timing of physical activity and measures of metabolic health in sedentary older people. METHODS: Hourly mean physical activity derived from wrist-worn accelerometers over a 6-day period was collected at baseline and after 3 months in sedentary participants from the Active and Healthy Ageing study. A principal component analysis (PCA) was performed to reduce the number of dimensions (e.g. define periods instead of separate hours) of hourly physical activity at baseline and change during follow-up. Cross-sectionally, a multivariable-adjusted linear regression analysis was used to associate the principal components, particularly correlated with increased physical activity in data-driven periods during the day, with body mass index (BMI), fasting glucose and insulin, HbA1c and the homeostatic model assessment for insulin resistance (HOMA-IR). For the longitudinal analyses, we calculated the hourly changes in physical activity and change in metabolic health after follow-up. RESULTS: We included 207 individuals (61.4% male, mean age: 64.8 [SD 2.9], mean BMI: 28.9 [4.7]). Higher physical activity in the early morning was associated with lower fasting glucose (-2.22%, 95% CI: -4.19, -0.40), fasting insulin (-13.54%, 95%CI: -23.49, -4.39), and HOMA-IR (-16.07%, 95%CI: -27.63, -5.65). Higher physical activity in the late afternoon to evening was associated with lower BMI (-2.84%, 95% CI: -4.92, -0.70). Higher physical activity at night was associated with higher BMI (2.86%, 95% CI: 0.90, 4.78), fasting glucose (2.57%, 95% CI: 0.70, 4.30), and HbA1c (2.37%, 95% CI: 1.00, 3.82). Similar results were present in the prospective analysis. CONCLUSION: Specific physical activity timing patterns were associated with more beneficial metabolic health, suggesting particular time-dependent physical activity interventions might maximise health benefits.

Older adults exercising ON TIME: protocol for a randomized controlled cross-over study to assess the effect of physical activity timing on insomnia severity.

BACKGROUND: There are increased indications that physical activity timing, irrespective of intensity, impacts insomnia and circadian clock function. Here, we describe the rationale and design of a randomized cross-over study, called ON TIME, to examine the effects of (changing) physical activity timing on insomnia severity and on multiple exploratory outcomes that are linked to circadian clock function. METHODS: We will conduct a randomized cross-over trial in 40 healthy older adults (aged 65 to 75 years) with subclinical or clinical insomnia (Insomnia Severity Index (ISI) scores of ≥ 10) from the Dutch municipality of Leiden and surroundings. Participants will undergo 3 intervention periods (14 days each) consecutively: one sedentary period and two periods of increased physical activity (one period with morning activity and one period with evening activity). The intervention periods are separated by a wash-out period of 1 week. In both active intervention arms, participants will follow coached or uncoached outdoor physical exercise sessions comprising endurance, strength, and flexibility exercises for 14 days. The primary outcome is change in insomnia severity as measured by the ISI. Additional exploratory outcomes include multiple components of objective sleep quality measured with tri-axial accelerometry and subjective sleep quality assessed by questionnaires as well as dim light melatonin onset and 24-h rhythms in heart rate, heart rate variability, breathing rate, oxygen saturation, mood, and objective emotional arousal and stress. Additionally, we will collect diary data on eating patterns (timing and composition). Finally, fasting blood samples will be collected at baseline and after each intervention period for measurements of biomarkers of metabolic and physiological functioning and expression of genes involved in regulation of the biological clock. DISCUSSION: We anticipate that this study will make a significant contribution to the limited knowledge on the effect of physical activity timing. Optimizing physical activity timing has the potential to augment the health benefits of increased physical exercise in the aging population. TRIAL REGISTRATION: Trial was approved by the Medical Ethics Committee Leiden, The Hague, Delft, The Netherlands (June, 2023). The trial was registered in the CCMO-register https://www.toetsingonline.nl/to/ccmo_search.nsf/Searchform?OpenForm under study ID NL82335.058.22 and named ("Ouderen op tijd in beweging" or in English "Older adults exercising on time"). At time of manuscript submission, the trial was additionally registered at ClinicalTrials.gov under study ID: NL82335.058.22 and is awaiting approval.

Setting your clock: associations between timing of objective physical activity and cardiovascular disease risk in the general population.

AIMS: Little is known about the impact of daily physical activity timing (here referred to as 'chronoactivity') on cardiovascular disease (CVD) risk. We aimed to examined the associations between chronoactivity and multiple CVD outcomes in the UK Biobank. METHODS AND RESULTS: physical activity data were collected in the UK-Biobank through triaxial accelerometer over a 7-day measurement period. We used K-means clustering to create clusters of participants with similar chronoactivity irrespective of the mean daily intensity of the physical activity. Multivariable-adjusted Cox-proportional hazard models were used to estimate hazard ratios (HRs) comparing the different clusters adjusted for age and sex (model 1), and baseline cardiovascular risk factors (model 2). Additional stratified analyses were done by sex, mean activity level, and self-reported sleep chronotype. We included 86 657 individuals (58% female, mean age: 61.6 [SD: 7.8] years, mean BMI: 26.6 [4.5] kg/m2). Over a follow-up period of 6 years, 3707 incident CVD events were reported. Overall, participants with a tendency of late morning physical activity had a lower risk of incident coronary artery disease (HR: 0.84, 95%CI: 0.77, 0.92) and stroke (HR: 0.83, 95%CI: 0.70, 0.98) compared to participants with a midday pattern of physical activity. These effects were more pronounced in women (P-value for interaction = 0.001). We did not find evidence favouring effect modification by total activity level and sleep chronotype. CONCLUSION: Irrespective of total physical activity, morning physical activity was associated with lower risks of incident cardiovascular diseases, highlighting the potential importance of chronoactivity in CVD prevention.