It's been said that breakfast is the most important meal of the day - but when you eat it may be just as significant as what you eat.

A new study from Mass General Brigham found that eating a late breakfast is "associated with an increased risk of death" among older adults. 

"Our research suggests that changes in when older adults eat, especially the timing of breakfast, could serve as an easy-to-monitor marker of their overall health status," nutrition scientist and lead study author Hassan Dashti said in a statement. "Patients and clinicians can possibly use shifts in mealtime routines as an early warning sign to look into underlying physical and mental health issues."

The study found that a later breakfast time was consistently linked to depression, fatigue and oral health problems, as well as bad sleep and trouble preparing meals. 

Eating a later breakfast is generally a habit of "night owls," the researchers said. A 2018 study found that those who stay up late have a higher risk of dying than those who go to bed and wake up early. 

The study looked at data and blood samples from about 3,000 people in the United Kingdom between 42 and 94 years old who were monitored for at least 20 years. As older adults age, they tend to eat breakfast and dinner at later times, the researchers found.

"Up until now, we had a limited insight into how the timing of meals evolves later in life and how this shift relates to overall health and longevity," Dashti said. "Our findings help fill that gap by showing that later meal timing, especially delayed breakfast, is tied to both health challenges and increased mortality risk in older adults."

The study says that encouraging older adults to eat meals at consistent times "could become part of broader strategies to promoting healthy aging and longevity."