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The Welsh Health Survey in the SAIL databank
Mark Atkinson, Jonathan Kennedy and Sinead Brophy
College of Medicine, Swansea University
Health Surveys User Conference, 10 July, 2015
Contents
• SAIL databank• Reasons for linking WHS data• Linkage to WHS data• Looking at a few example variables
o BMIo Smokingo Exerciseo Health Conditions
Datasets in SAIL
• We have a large variety of routine data; • GP (70 % coverage) • Hospital inpatient• Hospital outpatient• A&E• Education (National Pupil Database)• National Survey for Wales
Reasons for linking WHS data
1. To compare with a dataset with similar variables.a) Missing data in GP databaseb) Look at the WHS data which is more complete
2. To supplement the WHS data with additional information.
Comparison between datasets
WHS GP dataTime Single point Multiple pointsCoverage Nearly
CompleteIncomplete
Questions Identical Variable
WHSNot Present Present
GPNot Present 10 (3%) 175 (51%) 185 (54%)Present 11 (2%) 145 (43%) 156 (46%)
21 (6%) 320 (94%) 341
BMI – data in both datasets
BMI
Green line – gradient = 1
Red line, actual gradient of the data = 0.886WHS value 5 % smaller than corresponding GP value
Weights
Green line – gradient = 1
Red line, actual gradient of the data = 0.879WHS value 4.4 % smaller than corresponding GP value
Alcohol and Diet
• Alcohol– 79 % of those with GP data have GP data on alcohol
consumption under the 136.. Read code header
• Diet– 43 % of those with GP data have GP data on diet under any of
the three Read code headers• 1F% Dietary history• 13A% Diet – patient initiated• 13B% Diet - medical
Exercise
• 62 % of those with GP data have GP data on exercise under the 138 Read code header
WHSNo exercise Light Medium Heavy
GP
No exercise 6 <5 <5 <5Light 11 29 24 9Medium 5 11 32 19Heavy <5 <5 <5 8
Two types of missingness in GP data
1. Some have no relevant codes2. Some have ambiguous codes which carry no information
1st type In WHS, with GP data but no 138 codes
WHSNo Exercise 16 (14 %)Light 20 (18 %)Medium 46 (41 %)Heavy 31 (27 %)
2nd typeWhere GP exercisestatus is unknown
WHSNo Exercise 9 (21 %)Light 14 (33 %)Medium 15 (35 %)Heavy 5 (12 %)
Smoking
• 96 % of those with GP data have GP data on smoking under the 137 Read code header
• Note that people reporting in WHS as never smokers may have evidence from the GP data of being ex smokers
WHSmissing never ex smoker
GP
No information <5 9 <5 5never <5 65 5 <5ex <5 55 67 <5smoker <5 12 19 41
Health conditions
• Health conditions are notoriously under-reported in questionnaires
• The use of linked GP and hospital episode diagnoses will supplement WHS data