Kirby Nathalie V, Meade Robert D, McCormick James J, King Kelli E, Notley Sean R, Kenny Glen P
Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, 125 University Private, Montpetit Hall, Room 367, Ottawa, ON, K1N 6N5, Canada.
Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
Eur J Appl Physiol. 2025 Mar;125(3):769-780. doi: 10.1007/s00421-024-05623-y. Epub 2024 Oct 17.
Brain-derived neurotrophic factor (BDNF) is a neuroprotective growth factor that increases in young adults during short, intense bouts of passive heat stress. However, this may not reflect the response in heat-vulnerable populations exposed to air temperatures more consistent with indoor overheating during hot weather and heatwaves, especially as the BDNF response to acute stressors may diminish with increasing age. We therefore evaluated the ambient and body temperature-dependent responses of BDNF in older adults during daylong passive heating.
Sixteen older adults (6 females; aged 66-78 years) completed 8-h exposure to four randomized ambient conditions simulating those experienced indoors during hot weather and heatwaves in continental climates: 22 °C (air-conditioning; control), 26 °C (health-agency-recommended indoor temperature limit), 31 °C, and 36 °C (non-airconditioned home); all 45% relative humidity. To further investigate upstream mechanisms of BDNF regulation during thermal strain, we also explored associations between BDNF and circulating heat shock protein 70 (HSP70; taken as an indicator of the heat shock response).
Circulating BDNF was elevated by ~ 28% (1139 [95%CI: 166, 2112] pg/mL) at end-exposure in the 36 °C compared to the 22 °C control condition (P = 0.026; 26 °C-and 31 °C-22 °C differences: P ≥ 0.090), increasing 90 [22, 158] pg/mL per 1 °C rise in ambient temperature (linear trend: P = 0.011). BDNF was also positively correlated with mean body temperatures (P = 0.013), which increased 0.12 [0.10, 0.13]°C per 1 °C rise in ambient temperature (P < 0.001). By contrast, serum HSP70 did not change across conditions (P ≥ 0.156), nor was it associated with BDNF (P = 0.376).
Our findings demonstrate a progressive increase in circulating BDNF during indoor overheating in older adults.
脑源性神经营养因子（BDNF）是一种神经保护生长因子，在年轻成年人经历短暂、强烈的被动热应激期间会增加。然而，这可能无法反映易受热影响人群在炎热天气和热浪期间暴露于与室内过热更一致的气温下的反应，特别是随着年龄增长，BDNF对急性应激源的反应可能会减弱。因此，我们评估了老年人在全天被动加热过程中BDNF的环境温度和体温依赖性反应。
16名老年人（6名女性；年龄66 - 78岁）完成了8小时暴露于四种随机环境条件的实验，这些条件模拟了大陆性气候炎热天气和热浪期间室内所经历的情况：22°C（空调；对照）、26°C（卫生机构推荐的室内温度上限）、31°C和36°C（无空调的家庭环境）；所有条件相对湿度均为45%。为了进一步研究热应激期间BDNF调节的上游机制，我们还探讨了BDNF与循环热休克蛋白70（HSP70；作为热休克反应的指标）之间的关联。
与22°C对照条件相比，在36°C环境下暴露结束时，循环BDNF升高了约28%（1139[95%CI：166, 2112]pg/mL）（P = 0.026；26°C和31°C与22°C的差异：P≥0.090），环境温度每升高1°C，BDNF增加90[22, 158]pg/mL（线性趋势：P = 0.011）。BDNF也与平均体温呈正相关（P = 0.013），环境温度每升高1°C，平均体温升高0.12[0.10, 0.13]°C（P < 0.001）。相比之下，血清HSP70在各条件下均未改变（P≥0.156），也与BDNF无关联（P = 0.376）。
我们的研究结果表明，老年人在室内过热期间循环BDNF会逐渐增加。
