EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate, prospectively, the association between weight change and health-related quality of life in women.

Inclusion Criteria:

Subjects were participants in The Nurses' Health Study.

Exclusion Criteria:

Women who reported a diagnosis of cancer, angina, myocardial infarction, coronary revascularization or stroke prior to June 1996
Women whose data were missing on major covariates or had abnormal values for exercise or alcohol consumption per week.

Description of Study Protocol:

Recruitment

Data were used from The Nurses' Health Study, established in 1976, when 121,700 females aged 30 to 55 years were recruited to complete a mailed questionnaire about risk factors for cancer and cardiovascular diseases
Recruitment methods not described.

Design

Prospective cohort study.

Statistical Analysis

Analyses were stratified by baseline BMI and age group
Ordinary least squares regression was used in which SF-36 scores in 1996 were regressed on weight-change patterns.

Data Collection Summary:

Timing of Measurements

In 1976, subjects completed a mailed questionnaire about risk factors for cancer and cardiovascular diseases
Through the 20-year follow-up period at two-year intervals, each had completed a follow-up questionnaire to obtain information about as variety of health risk factors including body weight and major illnesses
In 1992 and 1996, the Medical Outcomes Study Short-Form 36 Health Status Survey (SF-36) was administered to the cohort.

Dependent Variables

Quality of life variables were measured by the completion the SF-36 questionnaire.

Independent Variables

Weight change.

Control Variables

BMI
Age group
Physical activity
Alcohol consumption
Smoking.

Description of Actual Data Sample:

Initial N: 67,247 women completed the SF-36 questionnaire and provided information on weight in 1992, 1994 and 1996
Attrition: The final study sample was 45,375
Age: 46 to 71 years old
Location: United States.

Summary of Results:

Key Findings

A total of 15,602 women (39%) maintained their weight. 15,160 (38%) gained between 2.25kg and 9.0kg (five to 20 lbs) and 6,667 (17%) lost between 2.25kg and 9.0kg (five to 20 lbs).
Weight gain in all age groups was associated with decreased functioning. A weight-gain of 20 lbs or more was associated with decreased physical functioning, vitality and increased bodily pain regardless of baseline BMI.
The odds ratio for developing role limitations due to physical problems was 2.05 (95% confidence interval, 1.69-2.49) for the leanest women, who gained 9.0kg (20 lbs) or more
Weight-gain over a four-year period was associated with decreased functioning among women younger than 65 years in every BMI category (less than 25kg/m², 25.0kg to 29.9kg/m², 30.0kg to 34.9kg/m² and at least 35.0kg/m²)
Women who gained weight also experienced increased risks of role limitations due to physical and emotional problems, compared with women who maintained their weight
Weight-loss in overweight women was associated with improved physical function and vitality and decreased bodily pain
Weight-change was more strongly associated with physical rather than mental health
Associations between weight-gain and quality of life among older women were similar to those observed in younger women. However, weight-gain was not associated with change in mental health in women over 65 years.
Weight-loss was associated with significant improvements in physical functioning among women in the two highest BMI categories (30.0kg to 34.9kg/m² and at least 35.0kg/m²). However, weight-loss was associated with decreased physical function, vitality, mental health and increased bodily pain in the leanest women (BMI<25kg/m²).
The impact of weight-change (especially weight-gain) was just as strong in women 65 years and older as in women younger than 65 years.

Author Conclusion:

These longitudinal data support current US guidelines for women of all body mass index levels to avoid weight gain. Weight maintenance, and in the case of overweight, weight loss are desirable and likely to be beneficial for physical function, vitality and bodily pain.

Funding Source:

Government:

National Institutes of Health

Not-for-profit

Boston Obesity/Nutrition Center

Other non-profit:

Reviewer Comments:

Authors note the following limitations:

Lack of availability of information describing whether or not weight-loss was intentional
Study population was based on women aged 46 to 72 years; the impact of weight change on functional health status in women in other age groups, specifically in younger women, might differ
Study population is not representative of the general United States population, but are comparable to similarly-aged groups of women working in the United States.

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)	N/A
	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)	N/A

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?	???
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)	Yes
	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.)	N/A
	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.)	N/A
	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?	Yes
	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?		No
	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.)	No
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	No
	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?	Yes
	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?	N/A
	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?	Yes
	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?		Yes
	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?	Yes
	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?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	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?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	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)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	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?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
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