You will be provided with a reference and some statements. Please determine whether each statement is 'supported', 'unsupported', or 'unknown' with respect to the reference. Please note:
First, assess whether the reference contains any valid content. If the reference contains no valid information, such as a 'page not found' message, then all statements should be considered 'unknown'.
If the reference is valid, for a given statement: if the facts or data it contains can be found entirely or partially within the reference, it is considered 'supported' (data accepts rounding); if all facts and data in the statement cannot be found in the reference, it is considered 'unsupported'.

You should return the result in a JSON list format, where each item in the list contains the statement's index and the judgment result, for example:
[
    {
        "idx": 1,
        "result": "supported"
    },
    {
        "idx": 2,
        "result": "unsupported"
    }
]

Below are the reference and statements:
<reference>
1. BMJ Open. 2017 Jun 23;7(6):e016795. doi: 10.1136/bmjopen-2017-016795.

The effect of magnesium supplementation on vascular calcification in chronic 
kidney disease-a randomised clinical trial (MAGiCAL-CKD): essential study design 
and rationale.

Bressendorff I(1), Hansen D(2), Schou M(3), Kragelund C(3), Brandi L(1).

Author information:
(1)Department of Cardiology, Nephrology, and Endocrinology, Nordsjællands 
Hospital, Hillerød, Denmark.
(2)Department of Nephrology, Herlev and Gentofte Hospital, Herlev, Denmark.
(3)Department of Cardiology, Herlev and Gentofte Hospital, Herlev, Denmark.

INTRODUCTION: Chronic kidney disease (CKD) is associated with an increased risk 
of cardiovascular disease and mortality, which is thought to be caused by 
increased propensity towards vascular calcification (VC). Magnesium (Mg) 
inhibits phosphate-induced VC in vitro and in animal models and serum Mg is 
inversely associated with cardiovascular mortality in predialysis CKD and in 
end-stage renal disease. This paper will describe the design and rationale of a 
randomised double-blinded placebo-controlled multicentre clinical trial, which 
will investigate whether oral Mg supplementation can prevent the progression of 
coronary artery calcification (CAC) in subjects with predialysis CKD.
METHODS AND ANALYSIS: We will randomise 250 subjects with estimated glomerular 
filtration rate of 15 to 45 mL/min/1.73 m2 to 12 months treatment with either 
slow-release Mg hydroxide 30 mmol/day or matching placebo in a 1:1 ratio. The 
primary end point is change in CAC score as measured by CT at baseline and after 
12 months treatment. Secondary end points include change in pulse wave velocity, 
bone mineral density, measures of mineral metabolism and clinical end points 
related to cardiovascular and renal events.
ETHICS AND DISSEMINATION: This trial has been approved by the local biomedical 
research ethics committees and data protection agencies and will be performed in 
accordance with the latest revision of the Helsinki Declaration. The trial will 
examine for the first time the effect of increasing the uptake of a putative VC 
inhibitor (ie, Mg) on progression of CAC in subjects with predialysis CKD.
TRIAL REGISTRATION NUMBER: NCT02542319, pre-results.

© Article author(s) (or their employer(s) unless otherwise stated in the text of 
the article) 2017. All rights reserved. No commercial use is permitted unless 
otherwise expressly granted.

DOI: 10.1136/bmjopen-2017-016795
PMCID: PMC5726116
PMID: 28645983 [Indexed for MEDLINE]

Conflict of interest statement: Competing interests: None declared.
</reference>

<statements>
1. Given that low serum magnesium is associated with higher cardiovascular event risk in chronic kidney disease (CKD), and that magnesium inhibits phosphate-induced vascular calcification in experimental models, a randomized trial (MAGiCAL-CKD) was conducted in predialysis CKD patients.
</statements>

Begin the assessment now. Output only the JSON list, without any conversational text or explanations.