In Reply Two comments by Sachdev and by Uzoigwe et al have addressed influences of latitude and other potential confounding factors in our study on the association between lithium in drinking water and the incidence of dementia.¹

There may be a north-south gradient in the prevalence of dementia in Scandinavia, but Denmark is considered too small for such an effect (368 km north to south). Further, there is no north-south gradient in lithium concentration in drinking water in Denmark, but rather an east-west gradient with lower concentrations in the western part of Denmark.^2,3 Therefore, our results cannot be explained by latitude of residence. However, other potential confounders cannot be excluded. Nevertheless, sources of lithium intake from diet or bottled water are unlikely to be systematically associated with place of residence and explain our findings. Thus, bioavailability of lithium in diet is less than from water, and bottled water consumption in Denmark is among the lowest in the European Union (20 L per person each year).²

在答复中，萨赫杰夫（Sachdev）和乌佐格威（Uzoigwe）等人的两项评论在我们关于饮用水中锂与痴呆症发病率之间关系的研究中解决了纬度和其他潜在混杂因素的影响。^1个

斯堪的纳维亚半岛的痴呆症患病率可能呈南北向梯度变化，但丹麦被认为对这种影响太小（北至南368公里）。此外，丹麦的饮用水中锂浓度没有北-南梯度，但丹麦西部的锂浓度没有东西向的梯度。^{2 ，3-}因此，我们的结果不能用居住的纬度来解释。但是，不能排除其他潜在的混杂因素。然而，从饮食或瓶装水中摄入的锂的来源不太可能与居住地有系统地关联，并可以解释我们的发现。因此，饮食中锂的生物利用度低于水，而丹麦的瓶装水消耗量在欧盟中是最低的（每人每年20升）。^2个