Sodium Intake in Populations Assessment of Evidence (2013) / Chapter Skim
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2 Approach to Evidence Review
2 Approach to Evidence Review
Pages 21-38
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From page 21... ...
The sources of evidence, questions that guided the literature search, the literature search strategy, and the process of selecting studies for detailed review are described, as are the criteria to critically appraise the individual studies. Finally, the chapter summarizes the advantages and limitations of different approaches used to estimate sodium intake, an important criterion that the committee used to assess the quality of the studies.
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From page 22... ...
These included the variability in methodological approaches used to evaluate relationships between sodium intake and risk of health outcomes, study design, limitations in the quantitative measures of both dietary intake and urinary excretion of sodium, confounder adjustment, and the number of relevant studies available. Assessing the impact of sodium intake on health outcomes was further complicated by wide variability in intake ranges among studies.
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From page 23... ...
What is the effect of reducing dietary sodium intake in individuals with hypertension, prehypertension, those aged 51 years and older, African Americans, and individuals with diabetes, chronic kidney disease, or congestive heart failure, compared to habitual intake on health outcomes (cardiovascular disease, myocardial infarction, diabetes, mortality, stroke, bone disease, fractures, falls, headaches, kidney stones, skin reactions, immune function, thyroid disease, or cancer)
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From page 24... ...
The specific outcomes were cardiovascular disease, congestive heart failure, hypertension, myocardial infarction, diabetes, mortality, stroke, bone disease, fractures, falls, headaches, kidney stones, chronic kidney disease, skin reactions, immune function, thyroid disease, and cancer. Table E-1 in Appendix E presents the search conducted in the MedLine database as an example of the searches conducted.
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4 RCTs, 21 2 observational 2 observational 2 observational 8 observational observational studies studies studies studies studies FIGURE 2-1 Flow diagram depicting the literature search strategy. NOTE: CVD, cardiovascular disease; RCT, randomized controlled trial.
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From page 26... ...
; relevance of the study's population, interventions, and outcomes measures; and the fidelity of implementation of interventions. The committee did not formally rate the studies for methodological quality because upon its review, it found the study designs were too varied and no generally accepted approach to performing such ratings for studies of dietary sodium existed.
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From page 27... ...
The relevance of the population under study to populations of interest in the statement of task (i.e., individuals with hypertension or prehypertension, those 51 years of age and older, African Americans, and individuals with diabetes, chronic kidney disease, and congestive heart failure) was used as an element of the evaluation.
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From page 28... ...
Examples of weaknesses in urinary excretion measures included potential systematic errors in measuring sodium intake due to incomplete 24-hour urine collections, lack of reporting urine creatinine levels or body weight, and lack of validation of spot urine collection methods. Examples of weaknesses in adjustment of confounders included exclusion of appropriate confounders in the analytical model (e.g., age, gender, use of antihypertensive medications, caloric intake, dietary potassium intake, or other risk factors for the relevant health outcome)
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From page 29... ...
Before 2003, a second dietary recall was collected for only a subset of respondents for quality assurance or to permit more accurate assessment of usual dietary intake. Beginning in 2001, a second recall was collected for a subset of respondents to permit more accurate assessment of usual dietary intake.
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From page 30... ...
. In summary, dietary sodium intake is a complex exposure, but it is possible to obtain useful information provided the right measures are used.
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From page 31... ...
. When evaluating spot urine specimens and indexing to urine creatinine, differences in muscle mass are another important consideration, as this is a major determinant of urine creatinine concentration and may therefore influence the spot urine sodium-to-creatinine ratio (Heymsfield et al., 1983)
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From page 32... ...
Some studies average 24-hour urine sodium over multiple collections, which is likely to improve accuracy as the measure of usual sodium intake. Another method is to assess the 24-hour urine creatinine excretion.
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From page 33... ...
In these individuals, the construct of spot urine sodium-to-creatinine ratio multiplied by the estimated creatinine excretion using the Kawasaki formula was correlated with measured 24-hour urine sodium excretion with a
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From page 34... ...
The committee agreed that while the spot urine sodium-to-creatinine ratio multiplied by the estimated creatinine excretion construct appears useful to rank order persons with respect to their sodium intake, the absolute level of estimated dietary intake is uncertain in non-Asian populations. In summary, multiple well-done 24-hour urine collections remain the gold standard method to assess dietary sodium intake, but bias due to inaccurate collection represents a major threat to validity.
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From page 35... ...
1993. Reproducibility and validity of food intake measurements from a semiquantitative food frequency questionnaire.
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From page 36... ...
2011. Validation of the equations for estimating daily sodium excretion from spot urine in patients with chronic kidney disease.
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From page 37... ...
2001. Comparative validation of the Block, Willett, and National Cancer Institute Food Frequency Questionnaires: The Eating at America's Table Study.
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