A relationship expert has suggested couples may be struggling due to a simple biological difference when it comes to sleep.
Making a relationship work usually takes effort from both people, along with a willingness to compromise and keep each other feeling supported.
That may sound straightforward, but day-to-day life can make things complicated, and disagreements can build from all kinds of unexpected sources.
Now, one relationship expert says some couples may be running into trouble for a reason they haven’t even considered — not necessarily stress, arguments, or a lack of communication, but differences in their natural sleep patterns.
Robyn Alesich, a relationship expert and matchmaker from Sister Wives, believes some partners are dealing with what she calls “chronotype clashes”.
A chronotype refers to your body’s built-in preference for when you naturally feel sleepy and when you’re most alert. It’s influenced by circadian rhythms — the internal 24-hour cycle that helps regulate hormones such as melatonin and cortisol — and it’s essentially the scientific explanation behind “early birds” and “night owls”.
Alesich said: “Most couples assume relationship problems stem from communication or stress, but they rarely consider that their body clocks might just be incompatible. Sleep incompatibility often threatens relationships without either person understanding why.”
“For example, one partner may feel ready for bed at 10pm while the other is most alert late into the night,” Robyn explains.
When partners are out of sync like this, it can spill into other parts of the relationship, creating friction that neither person immediately connects to sleep. Alesich also pointed to how common it can be, noting that ‘up to one-third of couples report being “sleep incompatible”.’
She added that research suggests couples with similar chronotypes tend to sleep better together than couples whose schedules naturally clash.
She continued: “While many couples struggle with intimacy and assume it’s an emotional issue, they don’t realize that biology could be a cause.
“Poor sleep affects everything from mood and patience to libido and emotional availability. If you’re sleeping worse because your partner’s body clock runs differently from yours, it can create a cycle of irritability, impacted emotional connection and lower intimacy.
“This can build up over time and make your relationship feel like it’s deteriorating. However, there are solutions.”
Alesich stressed that a mismatch in sleep timing doesn’t automatically mean the relationship is doomed.
Instead, she suggested there are practical adjustments couples can try to reduce the impact and protect both rest and connection.
She said: “If you’re worried about having mismatched chronotypes, it’s not always a dealbreaker. Couples who understand their biological differences can make adjustments, such as maintaining separate wind-down routines or agreeing on a ‘together window’ in the evening. Making small changes like this can dramatically improve both sleep and intimacy.”