(WTVO) — Metastatic breast cancer spreads more aggressively at night, according to a new study published in Nature.

The findings overturn an assumption that breast cancer metastasis happens at the same rate around the clock.

Researchers said they stumbled on the discovery after lab technicians working different shifts noticed differences in tumor cell samples analyzed at different times of the day.

Further studies could change the way doctors collect blood samples from cancer patients in the future.