The ACute Effects of Sitting Time on Physiological and Psychological Function in Older Adults

Sitting for extended periods has been linked to various health issues in older adults, including cardiovascular disease, type 2 diabetes, and mortality. However, the acute effects of sitting time on physiological and psychological function in this population are not well understood. This observational cohort study aimed to investigate the impact of acute periods of inactivity on key physiological and psychological outcomes in older adults.

Methodology and Study Design

The study employed a randomised cross-over design, where participants completed three separate days of sitting time: 1 hour, 2 hours, and 4 hours. The sitting times were conducted at the same time of day, and participants were allowed to watch television, knit, or read but not sleep. The primary outcome measure was lower limb power output using the Nottingham Power Rig (Watts (W)/kg). Secondary outcomes included a range of physiological and psychological measures, such as blood pressure, timed Up & Go performance, Digit Symbol Substitution (DSS) scores, and Profile of Mood State (POMS) related to vigour and friendliness.

Key Findings and Data Analysis

The study found that lower limb power output did not change significantly following the 1 hour, 2 hour, and 4 hour sitting times. However, a significant increase in mean systolic and diastolic blood pressure was recorded following the 2 hour and 4 hour sitting times. Mean arterial pressure also significantly increased after the 2 hour and 4 hour periods of sitting. Timed Up & Go performance declined after all sessions of sitting, whereas DSS scores and % DSS correct scores improved. Vitality declined across all sessions, but this was significantly worse after 4 hours. Psychological outcome measures related to vigour and friendliness showed significant adverse changes across all sessions, although vigour was worst after 4 hours sitting. Further, greater and negative fatigue changes were recorded after 2 and 4 hours sitting compared to 1 hour, with highest post-sitting values after 4 hours.

Physiological Outcomes

1. Lower Limb Power Output: Lower limb power output did not change significantly following the 1 hour, 2 hour, and 4 hour sitting times.
2. Blood Pressure: A significant increase in mean systolic and diastolic blood pressure was recorded following the 2 hour and 4 hour sitting times.
3. Mean Arterial Pressure: Mean arterial pressure also significantly increased after the 2 hour and 4 hour periods of sitting.
4. Timed Up & Go Performance: Timed Up & Go performance declined after all sessions of sitting.
5. Digit Symbol Substitution (DSS) Scores: DSS scores and % DSS correct scores improved.

Psychological Outcomes

1. Vitality: Vitality declined across all sessions, but this was significantly worse after 4 hours.
2. Vigour: Psychological outcome measures related to vigour and friendliness showed significant adverse changes across all sessions, although vigour was worst after 4 hours sitting.
3. Fatigue: Greater and negative fatigue changes were recorded after 2 and 4 hours sitting compared to 1 hour, with highest post-sitting values after 4 hours.

The study's findings suggest that sitting for 2 hours or more may have potentially deleterious effects on cardiovascular biomarkers, including blood pressure, as well as increasing the risk of falling. Vitality, vigour, and fatigue may also be adversely affected in older adults. These effects appear to increase with continuous sitting time.