EAL

DM: Prevention of Type 2 Diabetes (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the effect of body weight gain in early life on the age at diabetes diagnosis and to compare 2 different periods in adult life with regard to the association between weight change and diabetes risk.

Inclusion Criteria:

Women aged 35-65 y and men aged 40-65 y from the general population of Potsdam, Germany.

Exclusion Criteria:

Subjects with prevalent diabetes at baseline based on self-reported diagnosis, medication use, or dietary treatment and subjects with self-reported diabetes during follow-up but without physician confirmation were excluded.
In addition, subjects without follow-up information and missing confounder information at baseline for BMI, smoking, and alcohol use were excluded.
Subjects aged ≤ 40 y at baseline, subjects missing weight at ages 25 y and 40 y, and subjects with implausible BMI changes (gain of > 25 or a loss of > 15) during each weight-change period were excluded.

Description of Study Protocol:

Recruitment

Subjects were recruited from the general population of Potsdam, Germany from 1994 to 1998.

Design

Anthropometric measurements were obtained at baseline by trained staff following standardized procedures. A computer-based personal interview collected retrospective information about weight at ages 25 and 40. Information on education, smoking and alcohol consumption history were assessed with a self-administered questionnaire and a personal interview. Potentially incident cases of diabetes were identified on the basis of self reports of a diabetes diagnosis, use of diabetes-relevant medication, or dietary treatment. All potentially incident cases were verified by questionnaires that were mailed to the treating physician.

Blinding used (if applicable): Not applicable

Intervention (if applicable): Not applicable

Statistical Analysis

Cox proportional hazards models for type 2 diabetes to estimate adjusted hazard ratios and 95% CIs for changes in BMI were used. Linear regression was used to estimate the BMI change for a standardized 15-year period after age 40 y, BMI change between ages 25 and 40 y and BMI change between age 40 y and age at time of the baseline examination. Multivariate analyses included the covariates from baseline questionnaires including smoking history, alcohol consumption, physical activity and educational level. Wald's test was used to test hazard ratios for BMI change within different periods. Tests for linear trend were performed by using anthropometric characteristics, physical activity, and alcohol consumption as the continuous variable in a linear regression model and a test of independency (Cochran-Armitage trend test) was performed for categorical variables.

Data Collection Summary:

Timing of Measurements

Anthropometrics were collected at baseline and historical data was collected at the same time. 2 interviews were additionally administered 1 year apart to collect self-reported body weight at 25 and 40 y.

Dependent Variables

BMI change from age 25 y to age at 55 years

Independent Variables

Body weight in (kg) at baseline, 25y, 40y, 55y
Height at baseline
BMI at age 25y
BMI at age 40y
BMI at 55y
BMI difference between 25y and 40y
BMI difference between 40y and 55y
Physical activity (h/wk)
Alcohol intake (g/d)
Education (%) high school or less, more than high school
Smoking (%) Ever, never

Control Variables

Smoking status, alcohol consumption, physical activity and educational level were used as covariates in the multivariate analyses.

Description of Actual Data Sample:

Initial N: 16644 women and 10904 men

Attrition (final N): 10371 women and 7720 men

Age: Women were aged 35 -65 years; men 40-65 years

Ethnicity: Not noted by author

Other relevant demographics:

Difference in smoking status, physical activity and alcohol intake across BMI categories in men was not significant. Difference in physical activity and alcohol intake across BMI categories in women was not significant. Difference in smoking status across BMI categories was significant.

Anthropometrics

Percentage of subjects with less than a high school education was higher in women than in men and in subjects with a higher BMI at age 25 y than in leaner participants. Education level was significant across BMI categories for men and women.A higher prevalence of ex-smoking and current smoking was found in men than women.

Location:

Potsdam, Germany

Summary of Results:

Relative risk (RR) and 95% CI of type 2 diabetes for BMI change in (kg/m²) by compnents of BMI history

Variables

BMI at age 25 y

BMI change between ages 25 and 40 y

BMI change between ages 40 and 55 y

Men (n=7720)

Model 1

Model 2

1.15 (1.11, 1.20)

1.15 (1.11, 1.19)

1.26 (1.22, 1.31)

1.25 (1.21, 1.30)

1.14 (1.11, 1.17)

1.13 (1.10, 1.16)

<0.0001

Women (n = 10371)

Model 1

Model 2

1.11(1.07, 1.15)

1.24(1.20, 1.28)

1.24(1.20, 1.27)

1.12(1.09, 1.15)

1.11(1.08, 1.14)

<0.0001

Other Findings

Severe weight gain between the ages of 25 and 40 was associated with a higher diabetes risk in men (1.5 times) and in women (4.3 times) than were stable weight in early adulthood and weight gain in later life, and it resulted in an average lower age at diabetes diagnosis in men (5 y) and in women (3 y).

BMI at ages 25, 40, and 55 y differed for both sexes and all categories of BMI at age 25 y.

Author Conclusion:

Weight gain measured as the change in BMI in men and women in early adulthood (ages 25-40 years) was more strongly associated with risk of type 2 diabetes than was a subsequent increase in BMI. A greater weight gain, particulary in early adulthood, resulted in a younger age at onset of diabetes.

Funding Source:

Reviewer Comments:

Information on body weight at ages 25 and 40 years of age was self-reported. Body weight at 40 years was only tested for reproducibility and not for validity. This could have resulted in over- or underestimation of BMI gain in past times periods. The characteristics of body change of 15 years in early life (whether the participant gained weight continuously or whether weight cycling occurred) was not included.
BMI was calculated at 25, 40 and 55 years based on height collected at baseline only. Previous studies have shown a decrease in height in advanced age which would result in an increased BMI given a stable weight.
Retrospective data on body fat distribution were not available thus the relationship between obesity and type 2 diabetes might have been underestimated when BMI was used as the only anthropometric variable.
Physical activity was only considered in the 12 months before the baseline examination because information on physical activity throughout the adult life was not available. Physical activity may not have been adequately controlled for.
The age of diabetes diagnosis does not necessarily reflect the time of onset of diabetes and since all diagnoses were verified from a medical record it is possible that the participants who had greater contact with medical personnel had a higher probability of early detection of diabetes. The importance of age at diagnosis may therefore be underestimated.

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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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?		???
	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.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?		???
	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?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	???
	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