How a sleep doctor adapts to shorter days and shifting seasons

Shorter days, cooler mornings, and changing routines all affect how rested we feel, often more than we realize. Dr. Sohaib Imtiaz, a longevity physician and Chief Medical Officer at People Inc, explains that good sleep depends less on total hours and more on stable circadian cues that keep your rhythm steady as the seasons shift.

In his work as a medical advisor at Zest, he focuses on helping people understand the underlying rhythms that drive alertness and energy. Much of that comes down to timing, consistency, and strengthening the body’s internal clock.

Below, he breaks down the misconceptions he sees most often and the habits that make the biggest difference.

Rethinking what it means to feel rested

Most people assume more hours in bed equals better rest, but Dr. Imitaz says the equation isn’t that simple.

“Sleep quality is driven far more by efficiency and regularity,” he explains. You can hit eight hours yet still wake up groggy if your timing is inconsistent or your sleep architecture is disrupted.

In practice, it means the body responds more to rhythm than total hours. In other words, a stable sleep schedule does more for energy than squeezing in extra time on weekends.

Why winter light disrupts your internal clock

Darker mornings weaken one of the strongest circadian cues: light exposure. “Shorter days weaken the strength of your circadian signal,” he says, which can lead to delayed rhythms, lower morning alertness, and increased evening wakefulness — especially for anyone who already struggles to wake up early.

His simplest recommendation is to get bright light into your eyes quickly after waking and pair it with some early movement to reinforce your internal clock.

Simple routines that keep your circadian rhythm on track

Circadian rhythm can slip when changes in daylight and temperature shift, though small, consistent habits can keep it on track. Dr. Imtiaz suggests using cues help the brain recognize when it should wind down:

• wake up at the same time each day
• limit blue light and stimulation in the evenings
• keep your bedroom cool, dark, and quiet
• maintain a predictable wind-down routine

These can help the brain re-establish predictable rhythms even when the environment is changing.

How Zest supports a more reliable wake signal

Consistency is the hardest part of circadian alignment, especially in winter when sunlight is unpredictable. This is where he sees Zest playing a supportive role.

“By timing your morning alertness more predictably, it stabilizes your wake signal even when daylight becomes inconsistent,” he says.

For many people, it’s one more way to reinforce a rhythm the body can rely on.