Background

Several cohort studies with inaccurate estimates of sodium reported a J-shaped relationship with mortality. We compared various estimated sodium intakes with that measured by the gold-standard method of multiple non-consecutive 24-h urine collections and assessed their relationship with mortality.

Methods

We analysed the Trials of Hypertension Prevention follow-up data. Sodium intake was assessed in four ways: (i) average measured (gold standard): mean of three to seven 24-h urinary sodium measurements during the trial periods; (ii) average estimated: mean of three to seven estimated 24-h urinary sodium excretions from sodium concentration of 24-h urine using the Kawasaki formula; (iii) first measured: 24-h urinary sodium measured at the beginning of each trial; (iv) first estimated: 24-h urinary sodium estimated from sodium concentration of the first 24-h urine using the Kawasaki formula. We included 2974 individuals aged 30–54 years with pre-hypertension, not assigned to sodium intervention.

Results

During a median follow-up of 24 years, 272 deaths occurred. The average sodium intake measured by the gold-standard method was 3769 ± 1282 mg/d. The average estimated sodium over-estimated the intake by 1297 mg/d (95% confidence interval: 1267–1326). The average estimated value was systematically biased with over-estimation at lower levels and under-estimation at higher levels. The average measured sodium showed a linear relationship with mortality. The average estimated sodium appeared to show a J-shaped relationship with mortality. The first measured and the first estimated sodium both flattened the relationship.

Conclusions

Accurately measured sodium intake showed a linear relationship with mortality. Inaccurately estimated sodium changed the relationship and could explain much of the paradoxical J-shaped findings reported in some cohort studies.

中文翻译：

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川崎公式估算正常钠摄入量的错误改变了其与死亡率的关系：对公共健康的影响†

背景

几项钠盐估算不准确的队列研究报告了与死亡率呈J型关系。我们将各种估计的钠摄入量与通过多次非连续24小时尿液收集的金标准方法测得的钠摄入量进行了比较，并评估了它们与死亡率的关系。

方法

我们分析了高血压预防试验的随访数据。钠摄入量通过四种方式进行评估：（i）平均测量值（金标准）：在试验期间进行3至7次24小时尿钠测量的平均值；（ii）平均估计值：使用川崎公式从24小时尿液中的钠浓度估计出的3至7个24小时尿钠排泄物的平均值；（iii）首次测量：在每个试验开始时测量24小时尿钠；（iv）首次估算：使用川崎公式，从最初的24小时尿液中的钠浓度估算出24小时尿钠含量。我们纳入了2974例年龄在30-54岁之间的高血压前期患者，这些患者未分配钠盐干预。

结果

在24年的中位随访期间，有272人死亡。通过金标准方法测得的平均钠摄入量为3769±1282 mg / d。平均估计的钠含量高估了摄入量1297 mg / d（95％置信区间：1267–1326）。平均估计值在较低级别上被高估，而在较低级别上被低估了，因此存在系统偏差。测得的钠的平均含量与死亡率呈线性关系。估计的平均钠似乎显示出与死亡率呈J形关系。第一次测量的钠和第一次估计的钠都使该关系平坦。

结论

准确测量的钠摄入量与死亡率呈线性关系。钠的估计不正确改变了这种关系，并可能解释了一些队列研究报告的许多自相矛盾的J形发现。