Frequent sauna bathing and higher cardiorespiratory fitness (CRF) levels may play a role in reducing the risk of mental disorders such as psychosis, however, data on their joint contributions is scanty. We aimed to investigate the interplay between sauna bathing, CRF and psychosis risk using a population-based prospective study. Self-reported frequency of sauna bathing (FSB) and CRF measured by respiratory gas analyses were assessed at baseline in 2221 men aged 42–61 years who had no history of psychosis. Frequency of sauna bathing was categorized as low and high (≤2 and 3–7 sessions/week, respectively) and CRF as tertiles (low, medium and high). Hazard ratios (HRs) with 95% CIs were estimated. During a median follow-up of 25.2 years, 215 psychotic disorders were recorded. Comparing high vs low FSB, the multivariable-adjusted HRs (95% CIs) for psychosis was 0.49 (0.32–0.74), which persisted on further adjustment for CRF 0.50 (0.33–0.75). Compared to low CRF, the multivariable-adjusted HRs (95% CIs) for medium and high CRF levels were 0.65 (0.46–0.90) and 0.75 (0.52–1.07) respectively. Compared to low FSB & low CRF, the HRs (95% CIs) for low FSB & medium-high CRF, high FSB & low CRF, and high FSB & medium-high CRF were 0.62 (0.45–0.84), 0.26 (0.11–0.60), and 0.41 (0.25–0.68) respectively. Frequent sauna baths and medium-high CRF levels appear to each independently decrease psychosis risk. However, frequent sauna bathing may be related to a reduced risk of psychosis irrespective of fitness levels and might be a stronger risk indicator for psychosis than CRF.

中文翻译：

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经常洗桑拿和精神病：与心肺健康的相互关系

频繁的桑拿浴和较高的心肺健康（CRF）水平可能有助于降低精神病等精神疾病的风险，但关于它们共同作用的数据却很少。我们旨在通过一项基于人群的前瞻性研究来调查桑拿浴、CRF 和精神病风险之间的相互作用。对 2221 名 42-61 岁、无精神病史的男性进行了基线评估，对自我报告的桑拿浴频率 (FSB) 和通过呼吸气体分析测量的 CRF 进行了评估。桑拿浴频率分为低和高（分别≤2 次和 3-7 次/周），CRF 分为三分位数（低、中和高）。估计了 95% CI 的危险比 (HR)。在中位随访 25.2 年期间，记录了 215 种精神障碍。比较高 FSB 与低 FSB，精神病的多变量调整 HR (95% CI) 为 0.49 (0.32–0.74)，进一步调整 CRF 0.50 (0.33–0.75) 后仍保持不变。与低 CRF 相比，中和高 CRF 水平的多变量调整 HR (95% CI) 分别为 0.65 (0.46–0.90) 和 0.75 (0.52–1.07)。与低 FSB 和低 CRF 相比，低 FSB 和中高 CRF、高 FSB 和低 CRF、高 FSB 和中高 CRF 的 HR (95% CI) 分别为 0.62 (0.45–0.84)、0.26 (0.11–分别为 0.60) 和 0.41 (0.25–0.68)。频繁的桑拿浴和中高 CRF 水平似乎各自独立地降低了精神病风险。然而，无论健康水平如何，经常洗桑拿可能与降低精神病风险有关，并且可能是比 CRF 更强的精神病风险指标。