Continuous monitoring of 47 older adults across 14,179 nighttime hours revealed that bedroom temperatures exceeding 28°C (82°F) significantly compromised heart rate variability—a key marker of autonomic nervous system recovery during sleep. The study tracked real-world sleeping conditions in Australian homes, finding measurable cardiac stress responses when rooms became too warm overnight. This research fills a critical gap in sleep environment guidelines, as current WHO recommendations only address daytime indoor temperatures, not nighttime conditions. The cardiovascular implications are particularly relevant for aging populations, whose autonomic recovery systems are already compromised and who face increased vulnerability during heat waves. The findings suggest that nocturnal temperature control may be as important as daytime cooling for cardiac health, especially as climate change increases the frequency of uncomfortably warm nights. While the study's regional focus and modest sample size limit broader generalizability, the physiological mechanisms align with established research showing heat stress disrupts parasympathetic nervous system activity. For health-conscious adults, this represents actionable intelligence: bedroom cooling may directly support cardiovascular recovery, making nighttime temperature management a potentially underappreciated longevity strategy beyond mere comfort.