Overview

Spatial coverage

The data were collected for all Scotland.

Temporal coverage

  • May 1st 2001 to April 30th 2008 for cardiovascular diseases, cancer, breast cancer screening, mental health and maternal and child health.
  • May 1st 2001 to April 30th 2010 for respiratory diseases, gastrointestinal diseases and primary care (pilot)
  • May 1st 2001 to April 30th 2013 for the ongoing phase which aims to continue methodological work on the use of cardiovascular and respiratory risk factors from primary care and in addition, to study:
    • all-cause mortality
    • all-cause hospitalisation
    • hospitalisation and mortality for:
      • infectious and parasitic diseases
      • injuries, accident and poisoning
    • Uptake of bowel cancer screening and pathology of screen–detected bowel cancers

Species

Human population

Methods

Steps

The methods and many of the findings of our retrospective cohort study (SHELS) have been published [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. We followed a strict protocol that preserved anonymity and maintained separation of personal data from the Census and clinical data. Figure 1 shows our approach to linkage. We used computerised probability matching of names, sex, addresses and dates of birth to link the 2001 census for Scotland, to the Scottish Community Health Index (CHI), which is a register of patients using the NHS (National Health Service). At this stage, other data fields in the two datasets were excluded. CHI and the census unique numbers were encrypted. A one-way cryptographic (‘hashing’) algorithm was used to encrypt the CHI number. The census number was encrypted using an algorithm developed by the National Record of Scotland (NRS).

Figure 1 

Overview of record linkage process.

About 95% (approx 4.65 million) of the people participating in the 2001 census (4.9 million) were linked as above to the Scottish Community Health Index, with 85% or more linked in every ethnic group. This represents about 92% of the 2001 population. This linked file of encrypted CHI and census numbers is the key to subsequent linkage of any health data to the 2001 census records.

Using our retrospective cohort, we were able to analyse ethnic variations in various health and healthcare areas: cardiovascular diseases [2, 3, 4, 5, 6], cancer [7, 8, 9], maternal and child health [10], mental health [11], gastrointestinal diseases and respiratory diseases (to be submitted for publication in 2014). We have also linked primary care records from 10 general practices in Edinburgh and Glasgow.

Both hospitalisation diagnoses and causes of death (see tables 2 and 3 in appendix) were available in each health area dataset. Other health datasets were linked for the analyses of maternal and child health and mental health outcomes (see table 1 in appendix).

These morbidity and mortality data were examined in relation to ethnicity, adjusting for demographic and socioeconomic measures obtained from the 2001 census (See table 1 in appendix).

Sampling strategy

Not relevant here.

Quality Control

  1. The health data undergo quality control procedures by Information Services Division (ISD) of NHS National Services of Scotland. A Data Quality Assurance team ensure that the ISD health records are accurate, consistent and comparable across time and between sources. (http://www.isdscotland.org/Products-and-Services/Data-Quality/http://www.isdscotland.org/Products-and-Services/Data-Quality/ – accessed 17/09/2014, contact: nss.isd-dmdataquality@nhs.net)
  2. The Census data have undergone quality control procedures by NRS. (http://www.gro-scotland.gov.uk/files2/the-census/2001-census/census-assessment.pdf – accessed 17/09/2014, contact: customer@gro-scotland.gsi.gov.uk)
  3. Extracted datasets were checked and incidence figures calculated to compare to official published statistics.

Constraints

95% of the Census was linked to the CHI and at least 85% linkage was achieved for each ethnic group. In any health dataset, a small percentage of records were not linked for reasons including:

  1. CHI numbers not available or not linking to look up table
  2. A person was not in Scotland in 2001
  3. A person was not in the 2001 census

Privacy

Analytical datasets contain no personal identifiers. Statistical output is subject to a NRS disclosure protocol, and scrutiny by a disclosure committee. Researchers require government baseline security clearance for access to the data in a safe setting at NRS, as well as research governance training.

Ethics

The work was approved by the Multicentre Research Ethics Committee for Scotland and the Privacy Advisory Committee of NHS National Services Scotland, plus Community Health Index Advisory Group and Caldicott Guardian approval, where required.

Dataset description

Object name

SHELS data is not yet open access, for further information about the datasets see the tables in appendix. . A detailed metadata and data dictionary will be produced for each health extract once open access approval is agreed.

Data type

Secondary data, processed data.

Ontologies

None

Format names and versions

The datasets are stored in the safe haven as SAS dataset (.sas7bdat).

Creation dates

Creation date by health areas:

  • Cardiovascular disease: April 2009
  • Maternal and child health: October 2009
  • Mental health: December 2009
  • Cancer (including breast cancer screening): May 2010
  • Gastrointestinal diseases: June 2012
  • Respiratory diseases: November 2012
  • Primary care risk factors: April 2013
  • All-cause mortality: 2014 (ongoing)
  • All-cause hospitalisation: 2014 (ongoing)
  • Infectious and parasitic disease (including blood borne viruses): 2014 (ongoing)
  • Injuries, accident and poisoning: 2014 (ongoing)
  • Uptake of bowel cancer screening and pathology of screen–detected bowel cancers: 2014 (ongoing)

Dataset creators

A person independent of the core data analysis team linked the 2001 census numbers held by NRS to the CHI held by ISD, creating the SHELS look-up table with encrypted numbers. ISD extracted health datasets and NRS staff linked them to the Census using the look-up table held at NRS. Then, once the anonymised linked datasets were created, the SHELS researchers were responsible for the data analysis.

Language

English

Programming language

SAS (alternatively STATA) code was used to prepare and analyse the data. Programs are available upon request.

Licence

Not open licence

Accessibility criteria

The linked anonymised Census data and the health data are accessible on a stand-alone computer in a locked room at NRS. Currently, access is restricted to SHELS researchers who have security clearance.

Repository location

Not accessible for the moment, please contact the Principal Investigator (raj.bhopal@ed.ac.uk).

Publication date

Not applicable

Reuse potential

The datasets contain health and socioeconomic data for a wide range of health areas. NRS is currently assessing the feasibility of making SHELS data open access and potentially this could be reused by other researchers, with appropriate agreements from ethics and privacy advisory committees, to analyse the association between health in the Scottish population, as recorded in datasets with CHI number and any variable in the Census.

Appendix

Table 1

Health dataset showing census information.

Health information Census information

Dataset 1: CHD/Stroke
     - In patient and day-case discharge from the Scottish Morbidity Records SMR01 (general) database - Ethnic group
     - Mortality data from NRS - Religion, current
Dataset 2: cancers
     - In patient and day-case discharge from SMR01 and SMR06 (cancer registrations) databases - Religion of upbringing
     - Mortality data from NRS - Country of birth
     - Screening data from the Scottish Breast Screening Programme - Age
Dataset 3: maternal and child health
     - In patient and day-case discharge from SMR01 and SMR02 (maternity) database - Sex
     - Child health surveillance data - Long term illness
     - Scottish Birth Record data from NRS - Self-assessed health
     - Mortality data from NRS - Marital status
Dataset 4: mental health
     - In patient and day-case discharge from SMR01 and SMR04 (psychiatric) databases - Labour force status
     - Mortality data from NRS - Socioeconomic status
     - Data from the Mental Welfare Commission for Scotland - Highest qualification
Dataset 5: gastrointestinal
     - In patient and day-case discharge from SMR01 (general) database - Scottish Index of Multiple Deprivation decile
     - Mortality data from NRS - Car ownership
Dataset 6: respiratory
     - In patient and day-case discharge from SMR01 (general) database - Housing tenure
     - Mortality data from NRS - Household size
Dataset 7: all-cause hospitalisation*
     - In patient and day-case discharge from SMR01 (general) database - Numbers of rooms
     - Mortality data from NRS - Urban/rural indicator
Dataset 8: all-cause mortality*
     - Mortality data from NRS - Health board (Glasgow, Lothian, Tayside, Other)
Dataset 9: unintentional injuries and poisoning:*
     - In patient and day-case discharge from SMR01 (general) database - Mobile (temporary) accommodation
     - Mortality data from NRS - Self-contained accommodation
Dataset 10: all infectious and parasitic diseases*
     - In patient and day-case discharge SMR01 database - Central heating
     - Mortality data from NRS - Moved within last year
Dataset 11: hepatitis C, hepatitis B and HIV*
     - Records from the hepatitis C, hepatitis B and HIV datasets held by Health Protection Scotland - Economic activity last week
Dataset 12: bowel cancer screening*
     - Bowel Cancer Screening Key Performance Indicator (KPI) dataset held by ISD.
     - Cancer registrations SMR06 database
Dataset 13: Primary care (sample of 10 GP practices)
     - Cardiovascular and respiratory risk
     - Further linked to Dataset 1, 6 and 8
     - Limited data on morbidity and prescribed drugs relating to cardiovascular and respiratory diseases

* Under preparation

Table 2

SHELS health outcomes by health area for Phases 1-4 datasets (with outcomes between 2001 and 2013, minimum follow-up of 7 years).

Phase Health area Health outcomes

Phase 1/2 Cardiovascular diseases: - First myocardial infarction and survival (28-day)
- First chest pain
- First stroke
- First episode of heart failure
Mental Health - First psychiatric disorder (any diagnosis)
- First mood disorder
- First psychotic disorder
- Emergency detention certificate
- Short-term detention certificate
- Compulsory treatment order
Cancer - Any first cancer (excluding non-melanoma skin cancer)
- First lung cancer
- First prostate cancer
- First breast cancer
- First colorectal cancer
- Breast cancer screening non-attendance
Maternal and child health - Mean maternal age
- Mean gestational age
- Birthweight
- Proportion (%) of smokers (smoking history and smoking during pregnancy)
- Proportion of preterm birth
- Caesarean delivery
- Proportion of breast feeding at 6-8 weeks

Phase 3 Respiratory diseases - All-cause non cancer respiratory diseases
- Asthma
- COPD
- All upper respiratory infection
- Tonsillitis
- All lower respiratory infection
- Pneumonia
- Influenza
Gastrointestinal diseases - Peptic ulcer disease
- Oesophagitis
- Gastritis
- Gallstones
- Pancreatitis
- Irritable bowel syndrome
- Appendicitis
- Ulcerative colitis
- Crohn’s disease
- Any inflammatory bowel disease
- Diverticular disease
Primary care - Pilot study: data extraction and data quality assessment

Phase 4 Infectious diseases - Mortality/hospitalisation for infectious or parasitic diseases and incidence/prevalence for HIV and hepatitis C and B
Non intentional accidents - Mortality/hospitalisation for accidents, injuries and poisonings
Cancer - Participation in and outcome of the Scottish Bowel Cancer Screening Programme
Other - All-mortality
- All hospitalisation, length of stay and readmission
- Utilisation of morbidity and risk-factor data from primary care

* Under preparation

Table 3

Contents of Health Related Data.

Database Fields

General hospital discharge record (SMR01) linked to mortality Age in years
Sex
Admission date
Admission type
Admission reason
Duration of hospital admission
Days waiting
ICD diagnostic group
Main condition
Other condition
OPCS4 codes
Main operation
Date of the main operation
Other operation
Date of the other operation
Date of death if dead
Date of discharge
Discharge type
Discharge/transfer to
Inpatient/day case marker
Summarised admission code
Summarised discharge code

Maternity and birth record (SMR02) linked to mortality Age at admission (years)
Age at conception (years)
Type of antenatal care
Total previous:
Pregnancies
Spontaneous abortions
Therapeutic abortions
Caesarean sections
Still births
Neonatal deaths
Previous admissions this pregnancy
Parity
Date of booking
Original booking
Delivery plan-place
Delivery plan-management
Height of mother
Mother height group
Weight of mother
Type of abortion
Management of abortion
Sterilisation after abortion
Principal complication after abortion
Estimated gestation
Duration of pregnancy
Antenatal steroids
Diabetes
Smoking history (booking)
Smoker during pregnancy
Condition on discharge
Drug misuse (this pregnancy)
Drugs used 1-4
Ever injected illicit drugs
Typical weekly alcohol consumption
Indication of labour
Duration of labour
Analgesia during labour/delivery

Psychiatric inpatient records (SMR04) linked to mortality As for SMR01 plus:
Status on admission
Admission-referral from
Previous psychiatric care
Type of psychiatric care provided
Age on discharge (years)
Discharge-main condition
Discharge-other condition 1-5
ECT 1st treatment date
ECT treatments-no. this episode
Clinical facility start
Clinical facility end
Arrangements for aftercare 1-4
Care plan arrangements

Cancer registry (SMR06) linked to mortality Date of incidence/incidence date
Side
Site ICD9
ICD10 cancer site
ICDO2
Type ICDO
Morphology
Date of death
Vital status
Embarkation date
Cause of death 1-4
Death certificate only
Grade classification
Grade cell type
MVB diagnosis
Histological verification
Method 1st detection
Stage clinical T
Stage clinical N
Stage clinical M
Stage colorectal
Tumour size
Nodes examined
No of nodes examined
Positive nodes
Positive nodes no
ER status
Surgery
Date 1st surgery
Hosp GP 1st surgery
Referred to radiotherapy
Treated with radiotherapy
Date of 1st radiotherapy
Hospital 1st radiotherapy
Chemotherapy
Date 1st chemotherapy
Hospital GP 1st chemotherapy
Hormone therapy
Date 1st hormone therapy
Hosp GP 1st hormone therapy
Other therapy
Type other therapy
Date 1st other therapy
Hosp GP 1st other therapy

NRS death records Date of event
Primary cause of death
Secondary causes of death

Scottish Breast Screening data Date of death
Cancer found
Episode
Episode type
Episode invited
Episode attended
Episode outcome
Cancer diagnosis date
Facility flag
Referral flag

Child health data Birth details
Birthweight
Head circumference
Number born (current pregnancy)
Number born alive (current pregnancy)
Birth order (current)
Birth place type
Age of mother
Gestational age
Delivery mode
Onset of labour
Location
Early life/new born:
   - Feeding at 6 weeks
   - Neonatal care level
   - Newborn screening-all
   - Newborn status exam
Health makers:
   - Height
   - Weight
   - BMI
   - Immusation activity
   - History of present illness (?)
   - Significant health concerns
   - Sympathetic nervous system(??) status
   - Dental status
Basic health measurements
   - Height
   - Weight
   - BMI

Primary care risk factor data Date of registration
Date of deregistration
Tobacco consumption
Tobacco consumption date
Family history of disease
Family history of disease date
Exercise status
Exercise date
Diabetes
Diabetes date
CHD
CHD date
Stroke
Strokes date
Atrial fibrillation
AF date
Statins
Statins date
Height
Height date
Weight
Weight date
Cholesterol
Cholesterol date
Systolic blood pressure
Systolic blood pressure date
Diastolic blood pressure
Diastolic blood pressure date
Asthma
Asthma date
Asthma prescription
Asthma prescription date

Scottish Bowel Cancer Screening Program linked to cancer registry (SMR06) Date of test kit sent to participant
Health board of residence
Sex
Age in years
Screening test result
Flag for kit completed in error
Health board identifier/code
Date of notification of a screening result
Colonoscopy performed
Date colonoscopy performed
Reason for not having a colonoscopy
Colonoscopy completed
Invasive cancer detected
ICD-10 classification of neoplasm
Tumour classification (after surgery)
Nodal classification (after surgery)
Metastases classification (after surgery)
TNM classification of malignant tumour (tumour/nodal status/metastasis) derived Dukes’ stage
Polyps detected
Adenoma detected
Count of adenomas
Maximum dimension of the largest adenoma
Polyp cancer detected
Polypectomy performed at colonoscopy
Complication from the colonoscopy requiring admission
Death
Site ICD9
ICD10 cancer site
ICDO2
Type ICD 03
Grade cell type
Stage colorectal

General hospital discharge record (SMR01) linked to hepatitis B dataset from Health Protection Scotland (HPS) and mortality Sex
Age at diagnosis (years)
NHS board of residence (at diagnosis)
Date of earliest HBs Ag positive specimen
Source of 1st positive test (hospital, routine/antenatal screen, GP, other community setting)
HBV test result (recent/acute, chronic)
Date of late diagnosis
Late diagnosis indicator
Date of death
As for Hepatitis B plus:
Date of earliest positive specimen

General hospital discharge record (SMR01) linked to hepatitis C dataset from HPS and mortality Source of 1st positive HCV test (hospital, routine/antenatal
screen, GP, other community setting)
HCV test result
Description of result
HCV genotype
Risk group
Date of first attendance (specialist services)
Time from diagnosis to 1st attendance (specialist services)
Date started antiviral therapy
Time from diagnosis to start of antiviral therapy
Response to antiviral therapy (sustained viral response(SVR) non-SVR)

General hospital discharge record (SMR01) linked to HIV dataset from HPS and mortality As for Hepatitis B plus:
Date of earliest positive specimen
Source of HIV diagnosis test (hospital, routine/antenatal screen, GP, other community setting)
Risk group
Date of AIDS diagnosis (symptoms)
New case (known in Scotland or elsewhere/new to Scotland/unknown)
Infected outside to Scotland (yes/no)
Follow up status (attending/not attending/lost/dead/left Scotland/recent)
Date last attended healthcare services
Date of 1st attendance in HIV specialist care
Time from diagnosis to 1st attendance in HIV specialist care
Date of 1st attendance for CD4 measurement
1st CD4 results (category: low, medium, high)

* Under preparation