'It impacts sleep, diet, physical activity, and exposes workers to light at night' says scientist at BC Cancer Research Institute
“Night shift work is here to stay,” says Parveen Bhatti, distinguished scientist at the BC Cancer Research Institute. “We need to figure out a way to mitigate these risks.”
As part of a growing push to understand how work environments influence cancer risk, Dr. Bhatti investigates the biological impacts of night and rotating shift work on the human body. His current study, funded by the Canadian Cancer Society, focuses on how irregular work schedules might disrupt the gut microbiome — the complex system of trillions of bacteria in the digestive system — and how that disruption may increase the likelihood of developing cancer.
Bhatti’s concern stems from years of evidence linking night shift work to increased cancer risk, particularly for breast cancer, though associations with prostate and colorectal cancer also appear in emerging research.
“We’ve seen various studies showing increased risks of cancer among shift workers,” he explains. “Night shift work is a pretty complex exposure. It impacts sleep, diet, physical activity, and exposes workers to light at night — all of which may play a role.”
Unpacking the risk
Roughly 1.8 million Canadians work during overnight hours, many of them in critical sectors such as health care, emergency services, manufacturing, and resource industries. But scientific consensus on the carcinogenic potential of night work remains mixed.
Some global health authorities, including the International Agency for Research on Cancer (IARC), classify night shift work as a “probable human carcinogen,” while others continue to call for more robust, targeted studies. Bhatti’s research aims to fill that gap.
“When you look at the totality of evidence, especially with breast cancer, you do see increased risks,” he says. “Animal studies and cell research also show carcinogenic processes tied to circadian rhythm disruption.”
A major challenge, Bhatti notes, lies in how researchers define and measure night shift work. His team considers it any work schedule where individuals are active past midnight and finish by 6 a.m., representing a full flip from natural circadian rhythms.
Recruitment underway for key study
Bhatti is currently recruiting volunteers for a study titled Night Shift Work and Gut Microbiome, which aims to clarify how night work alters gut bacteria and may contribute to cancer risk. The research team seeks 200 night/rotating shift workers and 100 day shift workers from across British Columbia. Eligible participants receive a $100 reimbursement for approximately 70 minutes of total involvement.
Volunteers must meet the following criteria:
- Night/rotating shift workers: work an average of 2+ night shifts per week.
- Day shift workers: only work during the day.
What employers can do now
While research continues, Bhatti urges health and safety leaders to act now by supporting healthier lifestyles among night shift workers.
“Even for people not doing shift work, it’s hard enough to get enough sleep, eat well, and exercise,” he says. “For night workers, those challenges are even greater.”
He recommends that employers offer structured wellness programs tailored for overnight staff. These could include:
- Healthy meal options during night shifts
- Access to fitness resources or partnerships with local gyms
- Education on sleep hygiene and circadian rhythm health
- Regular health screenings to catch early signs of illness
“Anything that can make it easier for night workers to live a healthier life should be a priority,” Bhatti emphasizes. “We need to recognize that they face unique risks and challenges.”
As Canada observes Safety and Health Week, Bhatti’s research underscores a pressing issue in occupational health: recognizing and responding to the unseen, long-term risks of working outside the natural rhythms of day and night.
