Background: A decrease in sodium intake has been shown to lower blood pressure, but data from cohort studies on the association with cardiovascular and renal outcomes are inconsistent. In these studies, sodium intake was often estimated with a single baseline measurement, which may be inaccurate considering day-to-day changes in sodium intake and sodium excretion. We compared the effects of single versus repetitive follow-up 24-hour urine samples on the relation between sodium intake and long-term cardiorenal outcomes.

Methods: We selected adult subjects with an estimated glomerular filtration rate >60 mL/min/1.73m², an outpatient 24-hour urine sample between 1998 and 1999, and at least 1 collection during a 17-year follow-up. Sodium intake was estimated with a single baseline collection and the average of samples collected during a 1-, 5-, and 15-year follow-up. We used Cox regression analysis and the landmark approach to investigate the relation between sodium intake and cardiovascular (cardiovascular events or mortality) and renal (end-stage renal disease: dialysis, transplantation, and/or >60% estimated glomerular filtration rate decline, or mortality) outcomes.

Results: We included 574 subjects with 9776 twenty-four–hour urine samples. Average age was 47 years, and 46% were male. Median follow-up was 16.2 years. Average 24-hour sodium excretion, ranging from 3.8 to 3.9 g (165–170 mmol), was equal among all methods (P=0.88). However, relative to a single baseline measurement, 50% of the subjects had a >0.8-g (>34-mmol) difference in sodium intake with long-term estimations. As a result, 45%, 49%, and 50% of all subjects switched between tertiles of sodium intake when the 1-, 5-, or 15-year average was used, respectively. Consequently, hazard ratios for cardiorenal outcome changed up to 85% with the use of sodium intake estimations from short-term (1-year) and long-term (5-year) follow-up instead of baseline estimations.

Conclusions: Relative to a single baseline 24-hour sodium measurement, the use of subsequent 24-hour urine samples resulted in different estimations of an individual’s sodium intake, whereas population averages remained similar. This finding had significant consequences for the association between sodium intake and long-term cardiovascular and renal outcomes.

中文翻译：

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使用单个基线与多年期24小时尿液收集量估算长期钠摄入量及相关的心血管和肾脏风险

背景：钠摄入量的减少已被证明可以降低血压，但队列研究与心血管和肾脏结局的相关性数据不一致。在这些研究中，钠摄入量通常是通过单个基线测量来估算的，考虑到钠摄入量和钠排泄量的每日变化，这可能是不准确的。我们比较了单一和重复随访的24小时尿液样本对钠摄入量与长期心肾结局之间关系的影响。

方法：我们选择了估计肾小球滤过率> 60 mL / min / 1.73m ^2的成年受试者，在1998年至1999年之间门诊24小时尿液样本，并在17年的随访中至少收集了1次。钠的摄入量是通过一次基线收集以及在1年，5年和15年随访中收集的样品的平均值来估算的。我们使用Cox回归分析和标志性方法研究了钠摄入量与心血管（心血管事件或死亡率）与肾脏（终末期肾脏疾病：透析，移植和/或估计的肾小球滤过率下降60％以上）之间的关系。死亡率）结果。

结果：我们纳入了574名受试者的9776个24小时尿液样本。平均年龄为47岁，其中46％为男性。中位随访时间为16。2年。在所有方法中，平均24小时钠排泄量在3.8至3.9 g（165–170 mmol）之间（P = 0.88）。但是，相对于单个基线测量，长期估计的受试者中有50％的钠摄入量差异> 0.8 g（> 34 mmol）。结果，分别使用1年，5年或15年平均值时，所有受试者中分别有45％，49％和50％在钠摄入量之间切换。因此，使用短期（1年）和长期（5年）随访中的钠摄入量估算值代替基线估算值，可以使心脏肾结局的危险比变化高达85％。

结论：相对于单一的24小时基线基线钠盐测量，随后使用24小时尿液样品得出的个人钠摄入量估算值不同，而人群平均水平仍然相似。这一发现对钠摄入量与长期心血管和肾脏结局之间的关联具有重大影响。