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Reader questions
Reader questions
Reader questions
Reader questions, July 2026
Answers to the questions we were asked most this quarter: whether toppers fix sag, when a Split King is worth it, and adjustable base compatibility.
3 min read
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Sleep science contributor
Marcus Oyelaran
MSc Human Physiology · Registered Polysomnographic Technologist
Marcus Oyelaran holds an MSc in Human Physiology and spent nine years as a registered polysomnographic technologist in a hospital sleep laboratory, scoring overnight studies for apnoea, periodic limb movement and insomnia.
At Placemattress, Marcus writes the sleep guides and fact-checks every physiological claim the site makes. If a review says a mattress "helps with back pain", Marcus is the person who decides whether the evidence supports that sentence.
He is careful to point out where the research is thin. A mattress is one variable among many, and Marcus would rather say "we do not know" than repeat a marketing claim.
Areas of expertise
- Sleep physiology
- Polysomnography
- Temperature regulation during sleep
- Evidence review and medical fact-checking
Writing for Placemattress since 2022. Read our editorial policy and testing protocol.
Guides and journal entries
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Buying guide
Buying guide
Buying guide
Trial periods and warranties, read properly
Break-in clauses, return fees, sag thresholds and pro-rating. What mattress trial and warranty terms really commit the seller to, brand by brand.
4 min read
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Data
Data
Data
Do cooling covers work? We measured nine of them
Phase-change covers, gel infusions and copper threads, tested by swapping covers on the same mattress and logging surface temperature for eight hours.
3 min read