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DM: Physical Activity (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate the association between leisure time physical activity and glycemic control, insulin dose, and estimated insulin sensitivity in adult type 1 diabetic patients.
Inclusion Criteria:
All type 1 diabetic patients participating in the multicenter, nationwide Finnish Diabetic Nephropathy (FinnDiane) study who completed a validated 12-month questionnaire regarding leisure time physical activity.  All patients had type 1 diabetes, which was defined as diagnosis of diabetes before 35 years of age, permanent insulin treatment started within 1 year of diagnosis, and serum C-peptide concentrations <0.20 nmol/l.
Exclusion Criteria:
Patients with end-stage renal disease (hemodialysis or renal transplant) were excluded from the study.
Description of Study Protocol:

Recruitment

Patients participating in the Finnish Diabetic Nephropathy Study, a nationwide multicenter study.

Design

Cross-Sectional Study.

Blinding used (if applicable)

Not used - lab tests.

Intervention (if applicable)

Not applicable.

Statistical Analysis

For normally distributed variables, parametric tests (ANCOVA, ANOVA) were used.  Otherwise, nonparametric tests (Kruskal-Wallis) or logarithmic transformations were used.  For categorical variables, chi-square test was used.  For between-groups comparisons, P values for HbA1c were adjusted by ANCOVA for age, BMI and insulin dose, and P values for insulin dose were adjusted for age and BMI.  P values for eGDR were adjusted for age.  Correlations between insulin dose were adjusted for age and BMI, whereas correlations for eGDR were adjusted for age.

Data Collection Summary:

Timing of Measurements

Patients were grouped as sedentary, moderately active, and active.  Measurements made at one time.

Dependent Variables

  • HbA1c locally determined at each referral center
  • Serum C-peptide measured by radioimmunoassay
  • Urinary albumin excretion determined through overnight urine collection
  • Insulin dose
  • eGDR:  estimate of insulin sensitivity based on waist-to-hip ratio, hypertension and HbA1c
  • Weight
  • Height
  • Waist circumference
  • Blood pressure

Independent Variables

  • Physical activity quantified with validated questionnaire
  • Patients grouped as sedentary (<10 MET/week), moderately active (10-40 MET/week), and active (>40 MET/week)

Control Variables

  • Age
  • Obesity
  • Smoking
  • Insulin dose
  • Social class
  • Diabetic nephropathy
  • Cardiovascular disease

 

Description of Actual Data Sample:

Initial N: 1,030 type 1 diabetic patients, 482 males, 548 females

Attrition (final N):  1,030 patients.  Patients grouped as sedentary (n=247), moderately active (n=568), and active (n=215).

Age:  sedentary:  38 +/- 11 years, moderately active:  38 +/- 12 years, active:  37 +/- 12 years

Ethnicity:  not mentioned

Other relevant demographics:

Anthropometrics:  see results

Location:  Finland

 

Summary of Results:

 

All Patients

Sedentary

 Moderately Active Active P
HbA1c - Women (%) 8.8 +/- 1.4 8.3 +/- 1.4 8.3 +/- 1.4 0.004

HbA1c - Men (%)

8.4 +/- 1.3

8.2 +/- 1.4

 8.2 +/- 1.3

0.844
Insulin - Women (IU/kg/d) 0.71 +/- 0.22 0.71 +/- 0.23 0.66 +/- 0.22 0.036
Insulin - Men (IU/kg/d) 0.74 +/- 0.21 0.71 +/- 0.20 0.68 +/- 0.23 0.003
eGDR - Women (mg/kg/min) 6.8 (4.6 - 8.7) 7.4 (5.3 - 9.2) 7.3 (5.5 - 9.2) 0.038

eGDR - Men (mg/kg/min)

4.7 (3.5 - 7.4)

5.4 (3.9 - 8.1)

 5.5 (4.0 - 8.0)

0.052

Other Findings

Sedentary patients were more frequently men with greater BMI, decreased serum HDL cholesterol, and a greater prevalence of diabetic nephropathy than patients with greater levels of leisure time physical activity.

Leisure time physical activity correlated with HbA1c in women (r = -0.12, P = 0.007) but not in men (r = -0.03, P = 0.592).

Sedentary women had higher HbA1c than moderately active and active women:  8.8 +/- 1.4% vs 8.3 +/- 1.4% vs 8.3 +/- 1.4% (P = 0.004), whereas HbA1c in men was 8.4 +/- 1.3% vs 8.2 +/- 1.4% vs 8.2 +/- 1.3% (P = 0.774), respectively.

In men, insulin doses were 0.74 +/- 0.21 vs 0.71 +/- 0.20 vs 0.68 +/- 0.23 IU/kg/min (P = 0.003).

In both sexes, sedentary patients had lower eGDRs than active patients (median 5.5 vs 6.8 vs 6.7 mg/kg/min, P < 0.01 for sedentary vs others).

Age, obesity, smoking, insulin dose, social class, diabetic nephropathy or cardiovascular disease did not explain the results.

 

Author Conclusion:
Low levels of leisure time physical activity were associated with poor glycemic control in type 1 diabetic women.  Men seem to use less insulin when physically active.  Increased leisure time physical activity levels were associated with increased estimated insulin sensitivity.  Longitudinal studies are needed to further clarify the effects of leisure time physical activity on type 1 diabetes.
Funding Source:
Reviewer Comments:
Validated measurement of physical activity.  Large sample size.  Dietary habits not assessed in study.
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? 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) 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.) Yes
  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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  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.) N/A
  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? N/A
  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? N/A
  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? 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? 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? N/A
  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? 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? 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