Kawamura Minoru, Hashimoto Tomoko, Ogino Tadayoshi, Kaneko Hirosumi, Mifune Shinichi, Watanabe Tatsuo, Usui Yasuo, Tsuchikawa Goro, Shozushima Masakazu, Kudou Hiroshi
Department of General Internal Medicine, Iwate Prefectural Central Hospital, Japan.
Department of Internal Medicine, Ogino Hospital, Japan.
Intern Med. 2017;56(11):1321-1329. doi: 10.2169/internalmedicine.56.8270. Epub 2017 Jun 1.
Objective Although the daily urinary sodium excretion (UNaV) is considered to provide the most reliable estimate of the daily sodium intake, it may be affected by salt loss due to sweating in summer. However, the seasonal variation in the daily UNaV associated with a normal lifestyle is unknown. Methods This study was performed in 348 outpatients from the Morioka region during three seasons: summer (summer 1), winter, and the following summer (summer 2). The daily UNaV (g salt/day) was estimated by the second morning urine method three times during each season. Seasonal variation was defined as a significant trend across the three seasons together with a significant difference between winter and both summers. Results In women, the daily UNaV was higher in winter (11.8±3.0 g salt/day) than in summer 1 (11.2±2.9 g salt/day) or summer 2 (11.0±2.9 g salt/day). In contrast, there was no marked seasonal variation in men. An analysis stratified by age (4 quartiles) identified seasonal variation in the older 2 quartiles of women (aged ≥68 years). In these women, the mean seasonal difference in the daily UNaV was 0.9 g of salt/day for both winter vs. summer 1 and winter vs. summer 2, while it was 0.1-0.8 g of salt/day in the other groups. Conclusion Seasonal variation in the daily UNaV only occurred in older female patients and was relatively small. This is evidence for restricting salt intake throughout the year and should reassure patients who are anxious about salt loss due to sweating in summer.
目的 尽管每日尿钠排泄量（UNaV）被认为是对每日钠摄入量最可靠的估计，但它可能会受到夏季出汗导致的盐分流失的影响。然而，与正常生活方式相关的每日UNaV的季节性变化尚不清楚。方法 本研究在盛冈地区的348名门诊患者中进行，涵盖三个季节：夏季（夏季1）、冬季以及次年夏季（夏季2）。在每个季节通过第二次晨尿法对每日UNaV（克盐/天）进行三次估算。季节性变化定义为三个季节间的显著趋势以及冬季与两个夏季之间的显著差异。结果 在女性中，冬季的每日UNaV（11.8±3.0克盐/天）高于夏季1（11.2±2.9克盐/天）或夏季2（11.0±2.9克盐/天）。相比之下，男性中没有明显的季节性变化。按年龄（4个四分位数）分层分析发现，年龄较大的2个四分位数的女性（年龄≥68岁）存在季节性变化。在这些女性中，冬季与夏季1以及冬季与夏季2之间每日UNaV的平均季节性差异均为0.9克盐/天，而其他组为0.1 - 0.8克盐/天。结论 每日UNaV的季节性变化仅发生在老年女性患者中，且相对较小。这为全年限制盐摄入提供了证据，也应能让那些担心夏季出汗导致盐分流失的患者安心。
