# Exploratory Analysis of Association of Nightly Fasting and Sleep Durations with Colorectal Cancer Risk in Chinese Community-Dwelling Older Adults: A Cross-Sectional Study

## TL;DR

Longer nightly fasting increases colorectal cancer risk in older Chinese adults, while longer sleep reduces it, suggesting lifestyle adjustments could help prevent the disease.

## Contribution

Identifies nightly fasting and sleep durations as modifiable lifestyle factors linked to CRC risk in older Chinese adults.

## Key findings

- Each 1-hour increase in nightly fasting duration raises CRC risk by 9.5% in older adults.
- Longer nightly sleep duration is associated with a 15.2% lower CRC risk.
- Earlier dinner and later bedtime are linked to higher CRC risk.

## Abstract

Objectives: Disruptions in circadian-related behaviors are emerging as potential risk factors for gastrointestinal cancers. This study investigated the independent and joint associations of nightly fasting duration and sleep duration with the risk of colorectal cancer (CRC) among community-dwelling Chinese older adults. Methods: Participants were drawn from the Guangzhou CRC Screening Program, which used a questionnaire-based investigation, two separate fecal occult blood tests (FOBTs) for risk evaluation, and colonoscopy for high-risk individuals. Of the 347,297 people initially screened, 197,507 individuals were finally included after excluding 100,930 cases with missing eating/sleeping data or unknown/benign lesions via colonoscopy. Among the final sample, 351 CRC cases and 1384 precancerous lesions were diagnosed, while 195,772 individuals had negative results. Habitual times for dinner, breakfast, bedtime, and wake-up were used to define nightly fasting duration (dinner-to-breakfast) and nightly sleep duration (bedtime-to-wake). Multivariable logistic regression, subgroup analyses, and sensitivity analyses were performed to evaluate the associations. Results: In the fully adjusted models, each 1-h increment in nightly fasting duration was associated with a 9.5% (95% CI 1.039–1.153) higher risk of CRC, and the direct association was limited to individuals over 60 years (OR = 1.147, 95% CI 1.073–1.226), while each 1-h increment in nightly sleep duration was associated with a 15.2% (95% CI 0.806–0.893) lower risk of CRC. Consistently, earlier dinner, later breakfast and later bedtime were also associated with a higher CRC risk. Conclusions: In Guangzhou older residents, long nightly fasting duration was a risk factor for CRC, especially among individuals over 60 years old; while long nightly sleep duration was protective. These findings suggest that maintaining adequate sleep and optimizing the nightly fasting window may be viable lifestyle strategies for CRC prevention, emphasizing the need for tailored preventive measures for different age groups.