Surveillance and Surveys

1
Surveillance and Surveys

• Higher Blood pressure among Inuit migrants in
  Denmark than among Inuit in Greenland
• Bjerregaard et al

2
Small group members

• Lisa Langsetmo
• Kateri Champagne
• Dana Teltsch
• Christel Renoux

3
Basic Information

• Study of prevalence
• Blood pressure
• Inuit in Greenland in Denmark
• 1216 participants in Greenland
• 680 participants in Denmark

4
Research Question

• The purpose of this study was to compare the
  blood pressure between the Inuit of Greenland and
  the Inuit migrants in Denmark. Genetics (Inuit
  blood quantum), body mass index, education,
  smoking, alcohol, diet, and physical activity
  were analysed as possible determinants and
  confounders

5
Sampling

• Greenland
• Two cities and four villages selected
• Nuuk (random sample)
• Quasigiannguit (all)
• Uummannaq villages (all)

• Denmark
• Population register of people born in Greenland
• Random sample of young and everyone over 45
  mailed questionnaire
• Random sample of respondants who were Inuit
  invited to participate

6
Critique

• Are study design and sampling methods appropriate
  to research question?
• Study design is cross-sectional, outcome is
  prevalence. Appropriate.
• Research question is comparison, sampling in two
  settings is different. Greenland sample is large,
  not clear it is representative. Denmark sample is
  random, but with response on first stage 77 and
  on second stage 55 possible selection bias.

7
Critique

• Is the sampling frame appropriate?
• Sampling frame in Denmark is population register.
  Appropriate
• Sampling frame in Greenland is selected towns,
  villages. No explanation is given. Was any
  attempt made at being representative? Was any
  attempt made at including towns and villages of
  different sizes, socio-economic status?

8
Critique

• Is the sample size adequate?
• Overall sample size is good (1216 and 680)
• Some strata were relatively small (e.g. over 65)
• Some categories of confounders were merged in
  analysis (e.g. 1-14 cigarettes/day)
• Characteristics of Denmark and Greenland sample
  were very different (e.g. 27 vs 45 male, 51 vs
  89 full Inuit heritage)

9
Critique

• Are objective, suitable, and standard criteria
  used to measure outcome?
• Blood pressure measured in hospital, resting,
  standard equipment, right arm, appropriate sized
  cuff, and averaged values
• Unspecified detailed procedure, what is described
  in paper is not standard in Canada

10
Critique

• Is the outcome measured in an unbiased fashion?
• Different times (8 a.m.-2 p.m. vs 8 a.m.-8 p.m.)
• Different conditions (fasting and non-fasting)
• Unspecified observer training, procedure details,
  inter and intra observer reliability, and blinding

11
Critique

• Is response rate adequate?
• Greenland response rate was 66 Borderline
• Denmark response rate was 54 Not good
• Both were from non-random samples
• Real rates smaller due to exclusions
• Are the refusers described?
• Basic demographics known, reasons unknown
• Demographics outside sample frame unknown

12
Critique

• Are the estimates of prevalence and incidence
  given with confidence intervals and in detail by
  subgroup?
• Confidence intervals are given for whole groups
  and by subgroups where appropriate
• Procedure used to calculate them unclear.
• P-values also given. Unclear reason

13
Critique

• What are the implications of the results for
  action or intervention?
• Found difference in mean blood pressure between
  residents of Greenland and Denmark not explained
  by other measured variables
• Differences were consistent across categories of
  age and gender
• Found strong correlation with educational
  background, which may be a proxy for
  modernization

14
Critique

• Other comments
• Possible selection bias
• Possible observation bias
• Missing data
• Populations were very different
• Measurement of variables
• BMI, alcohol, physical activity

15
Comments

• Natural extensions of study
• How does blood pressure of migrants differ from
  the general Danish population
• How does the blood pressure of Greenlanders vary
  according to modernization