EAL

NNNS: Nutrient Quality (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

Data is presented from a recently begun cohort mortality study in which information gathered at baseline made it possible to analyze the relationship between past artificial sweetener use and weight change over the one-year period prior to enrollment.

Inclusion Criteria:

Over 30 years of age, whom the volunteers knew well enough to keep track of for at least the six-year study period
White women
Ages 50 to 69
At least a high school education
No history of diabetes, heart disease or cancer, conditions that may affect both weight and dietary behavior (including artificial sweeteners)
Lifelong smokers and current and former smokers whose smoking status had not changed for at least five years
Those who had never used arificial sweeteners or who were long-term current users, defined as those who answered "yes" currently to the usuage question and who had used packets, tablets, drops and diet beverages for a least 10 years.

Exclusion Criteria:

Those who said their diet had undergone a major change in the past 10 years, which might have led to weight change
Former artificial sweetener users.

Description of Study Protocol:

Recruitment: In September 1982, 77,437 American Cancer Society volunteers enrolled 1.2 million men and women from all 50 states, the District of Columbia and Puerto Rico.
Design: The subjects were not selected at random. Follow-up in 1988 bi-annually
Blinding used: Questionnaires; subjects filled them out and returned to volunteers in a sealed, confidential envelope
Statistical analysis: Restricted analysis to a homogeneous subgroup. All anlayses were statified by initial relative weight, computed as the quetelet index (QI=weight/height²). Data reported separately for five strata of QI.

Data Collection Summary:

Timing of Measurements

Questions at baseline:

Age
Current weight
Weight one year ago
Height
Whether a major change took place in your diet within the past 10 years
Do you now or have you ever added artificial sweeteners (saccharin or cyclamates) to coffee, tea or other drinks and foods?
If ever, how long and amount per day, form taken, quantity and duration of both current and former use of diet soda and diet iced tea.

Food consumption: Asked consumption frequency (days per week) of each of 28 food items including beef, poultry, specific fruits and vegetables, breads and potaotes among others.

Description of Actual Data Sample:

Initial N: A total of 78,694 women out of original cohort of 685

748 women met criteria
17,016 long term AS users (21%)
61,678 non-users.

Age: 50-69
Location: USA.

Summary of Results:

Age-Specific Usage

Overall proportion of AS users increased with QI from 12.9% in the lowest quintile to 29.8% in the highest. In each age group, AS usuage increased with relative weight and decreased with increasing age at each relative weight level.
No significant differences between age-adjusted percentages of AS users and non-users who lost weight at any initial weight level. Rate of weight gain in AS users was significantly greater than in non-users, irrespective of initial weight, the difference ranging from 2.7% in the leanest quintile (P=0.008) to 9.1% in the next-to-most-obese (P<0.001). The proportion of AS users who gained 10 pounds or more was significantly greater than the proportion of non-users who gained 10 pounds or more at each weight level.
The proportion of AS users who lost 10 pounds or more was not significantly different from that of non-users, except among the most obese, where 2.0% more users than non-users lost at least 10 pounds. (P<0.001).
Among women who gained weight, AS users, on average, gained significantly more weight than did non-users, regardless of initial QI (P<0.001). Differences in gains between users and non-users ranged from 0.6 to 1.5 pounds.
Women who lost weight: There were no differences in weight loss between AS users and non-users of average QI or less. AS users in the two heaviest groups lost an average of 0.7 to 1.4 pounds more than did non-users in the same categories (P<0.001).

Food Frequency Consumption

There were no differences in the mean number of times per week AS users reported eating beef, pork, liver, ham, smoked meats, franks or sausages, carrots, squash, citrus fruits or juices, cereal or oatmeal, ice cream or chocolate.
Differences in food consumption: AS users consumed green leafy vegetables, tomatoes, cabbage, chicken and fish significantly more than non-users. They consumed butter, white bread and potatoes significantly fewer times per week than non-users.

Author Conclusion:

Limitations and Advantages

Large sample size, which provides statistical power on 10 important variables and eliminates bias
Exclusive use of internal comparisons reinforces the study validity within this subpopulation. Further analysis would be needed to extend the findings to women not meeting the inclusion criteria.
Changes in weight between two points in time were used and bias and overestimation by individuals should be minimized.
Results are predominantly for saccharin.

Conclusion

The data do not support the hypothesis that long-term AS use either helps in losing weight or prevents weight gain.

Funding Source:

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	No
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	Yes
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		No
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	No
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	No
	7.5.	Was the measurement of effect at an appropriate level of precision?	No
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		No
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		No
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	No
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes