What does this research mean for the field?

Nighttime bedroom temperatures above 24 °C significantly increase the odds of clinically relevant reductions in heart rate variability and elevate heart rate in older adults. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

What question did this study set out to answer?

To examine the association between nocturnal bedroom temperatures and wearable-derived measures of heart rate and heart rate variability in community-dwelling older adults.

January 10, 2026BMC MedicineOpen Access

Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study

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Key result

Nighttime temperatures >24°C linked to ~190% higher odds of reduced HRV and elevated heart rate.

P < 0.001

Why the study?

Increasing hot nights may impair sleep and autonomic recovery, but unlike daytime indoor temperature guidelines, no equivalent recommendations exist for nighttime conditions.

Does elevated nighttime bedroom temperature reduce heart rate variability and increase heart rate in older adults?

Key Points

To examine the association between nocturnal bedroom temperatures and wearable-derived measures of heart rate and heart rate variability in community-dwelling older adults.
Enrolled 47 community-dwelling adults aged ≥ 65 years (median age: 72 years; 68% female) across one summer (December 2024–March 2025) in southeast Queensland, Australia.
Monitored nocturnal sleep periods (9 PM–7 AM) using wearable devices to capture heart rate and heart rate variability, alongside in-home sensors continuously recording bedroom temperature.
Employed generalized mixed-effects models to analyze associations across temperature categories (< 24 °C, 24–26 °C, 26–28 °C, 28–32 °C) across 14,179 valid nighttime hours, defining clinical relevance as a ≥ 1.5 SD change in HRV or a ≥ 5 beats·min⁻¹ change in heart rate.
Compared with temperatures < 24 °C, bedroom temperatures of 24–26 °C (OR: 1.4, 95% CI [1.2, 1.6], P < 0.001), 26–28 °C (OR: 2.0, 95% CI [1.8, 2.3], P < 0.001), and 28–32 °C (OR: 2.9, 95% CI [2.5, 3.4], P < 0.001) were associated with greater odds of clinically relevant reductions in lnRMSSD.
Elevated bedroom temperatures were associated with increased odds of heart rate elevations ≥ 5 beats·min⁻¹ at 24–26 °C (OR: 1.2, 95% CI [1.1, 1.3], P = 0.004), 26–28 °C (OR: 1.9, 95% CI [1.7, 2.1], P < 0.001), and 28–32 °C (OR: 3.9, 95% CI [3.5, 4.4], P < 0.001).
Higher temperatures were also significantly associated with decreases in lnHF and lnLF, alongside increases in the ln(LF:HF) ratio (all P ≤ 0.001), indicating autonomic disruption.

Structured PICO

Does elevated nighttime bedroom temperature reduce heart rate variability and increase heart rate in older adults?

Population

47 community-dwelling adults aged ≥ 65 years (median age 72, 68% female) in southeast Queensland, Australia. Key inclusion: non-smoking, English speaking, willing to wear a heart rate and activity monitor on their wrist for the duration of the summer-long observational period.

Intervention

Nighttime bedroom temperatures ≥ 24 °C (categorized as 24–26 °C, 26–28 °C, and 28–32 °C) continuously monitored via in-home sensors during sleep periods between 9 PM and 7 AM.

Comparator

Nighttime bedroom temperatures < 24 °C.

Outcome

Natural logarithm of the root mean square of successive differences (lnRMSSD) derived during nighttime (9 PM–7 AM) sleep.surrogate

Nocturnal bedroom temperatures above 24 °C are associated with autonomic disruption and increased heart rate in older adults, highlighting the potential need for nighttime indoor temperature guidelines to mitigate cardiovascular strain.

Limitations

Small, homogeneous sample of older adults residing in a sub-tropical climate, whom had likely garnered some level of heat acclimatization
Use of wearable-grade devices relying on proprietary algorithms to derive HRV metrics
Unmeasured participant use of active and passive interventions (e.g., fans, natural ventilation) that may have increased evaporative heat loss

Discussion

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Implication

May warrant caution on high nighttime bedroom temperatures in older adults; hypothesis-generating for temperature guidelines and needs prospective confirmation.

Cite This Study

O’Connor et al. (2025) studied this question. Nighttime bedroom temperatures above 24 °C significantly increased the odds of clinically relevant reductions in heart rate variability and elevated heart rate in older adults (OR up to 2.9; P < 0.001.

synapsesocial.com/papers/6963221491e05aa366cb8875 https://doi.org/10.1186/s12916-025-04513-0

Topics

Heart failure HFrEF treatment

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Implication

May warrant caution on high nighttime bedroom temperatures in older adults; hypothesis-generating for temperature guidelines and needs prospective confirmation.

Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study

Key Points

Structured PICO

Limitations

Discussion

Implication

Cite This Study

Topics

Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study

Key Points

Structured PICO

Limitations

Discussion

Implication

Cite This Study

Also Consider

Topics

Also Consider