Background
Objectives
Methods
Ethical approval
Study design
The CPRD database
Recruitment
Practices
Participants and recruitment
1) The CPRD advertised the study to practices already participating in CPRD data collection; volunteer practices were identified and made known to the research team. Their practice managers were approached. |
2) The research team provided each practice with a model letter from GP to patient introducing the study and the researchers. One generic letter was signed by a doctor in the practice and returned to the research team for copying and inclusion in mailings to patients. |
3) The CPRD sent each practice manager an electronic file listing the CPRD-coded identifier and a special study code number for each patient from the practice eligible to take part in the study (those born between 1948 and 1962 inclusive). |
4) A member of the practice staff added the name and address of each patient to this file. |
5) The GP excluded any patients from the mailing list whom he or she felt should not be approached (e.g., because of terminal illness or recent bereavement). |
6) A member of the practice staff printed an address label for each of the remaining patients, including the study code number and the name and address. |
7) The research team delivered to each practice a set of sealed envelopes with postage pre-paid, each marked with a study code number. |
8) Practice staff attached the appropriate address label to each envelope and mailed them. Envelopes for patients withdrawn from the study were counted and destroyed. |
9) Questionnaires were returned directly to the research team. Consent to baseline self-completed information was signified by return of a questionnaire. Additionally, participants were asked to complete and return a signed consent to the further stages of data linkage and postal follow-up, and to provide their name and contact details to the research team to enable follow-up without need for further involvement of the practices. |
Baseline questionnaire
Domain | Variables |
---|---|
Demographic and anthropometric characteristics | Age, sex, height and weight, marital status, ethnic origin, qualifications and education, household composition |
Current work status | Employed, self-employed, unemployed, or retired; more than one job; left last job for a health reason; receiving an ill-health pension |
Content and characteristics of paid work | Main occupation, length of service, pattern of work (e.g., salaried vs. piece work, permanent vs. temporary, shift and night working, income protection in illness, flexibility of working hours) and employer’s size; physical demands of work (e.g., regular kneeling, climbing, digging, lifting, and standing) |
Perceptions about work | Psychosocial demands, support from colleagues or manager, decision latitude, self-assessed ability to cope with the physical and mental demands of work; worry or anger about work; other feelings about work, e.g., satisfaction with work schedule, pay, and the job overall, conflicts at work and relational justice, perceived job security |
Perceptions about retirement | Retirement expectations, ambitions and plans (e.g., expected and ideal retirement age) |
Financial status | Housing tenure, affordability of consumer durables, contribution to total household income, pension provision, financial responsibility for others |
Social | Leisure and social activities; smoking and alcohol history; workplace friendships; caring and voluntary responsibilities |
Health | Self-rated health (SRH) [22]; an abridged Sleep Problems Scale [23]; five items from the somatising subscale of the Brief Symptom Inventory (BSI) [24]; the Center for Epidemiologic Studies Depression Scale (CES-D) [25], the Warwick-Edinburgh Mental Well-being Scale (WEMWBS) [26]; certain items on frailty (based on the Fried frailty index [27]), and hearing and memory impairments; chronic regional pain in the past 12 months; sickness absence in the past 12 months; presenteeism |
Occupational outcomes
Measures of health
Conditions of paid work
Physical working conditions
Psychological factors (including feelings about work)
Social and financial circumstances
Follow-up
CPRD-linked data
-
All hospital admissions, including all discharge diagnoses and procedures
-
All GP consultations for musculoskeletal disorders (MSDs)
-
All GP consultations for mental health problems
-
All GP consultations for asthma or COPD
-
All GP consultations for cardiovascular problems
-
All GP consultations for diabetes and epilepsy
-
All prescriptions related to these health problems (e.g., anxiolytics, hypnotics, sedatives, antidepressants, antipsychotics, narcotics, circulatory drugs, insulin, oral hypoglycaemics, antiepileptic medicines)
-
All injuries likely to be occupational
-
Frequency of GP consultations for all reasons combined
-
Any records of height, weight, BMI, smoking habits, alcohol consumption.
Plans for analysis
Study question | Independent variable | Dependent variable | Covariate (s) |
---|---|---|---|
Effect of work on health | |||
Employment status as a predictor of health decline or improvement | E1
| ΔH1–2
| C1
|
Job change (e.g., new unemployment, planned retirement) as a predictor of health change | ΔE1–2
| ΔH2–3
| H2, C2
|
Longer term effects of employment status | E1
| ΔH2–4, ΔH3–4
| H2, C2
|
ΔE1–2
| ΔH2–4, ΔH3–4
| ||
Effect of health on work | |||
Health as a predictor of job transition | H1
| ΔE1–2
| C1
|
Impact of health change on job status | ΔH1–2
| ΔE2–3
| E2, C2
|
a) Effect of health on work: | |
---|---|
Predictor variables | Outcome variables |
Health or change in health | Employment status: unemployed, retired, ill-health retired, temporarily off sick, employed, other role (e.g., carer) |
1) CPRD record: diagnosis (or treatment/worsening) of arthritis, soft tissue rheumatism, or other MSDs; or in those with MSDs, of concurrent… anxiety, depression, neurotic illness, insomnia, cardiovascular disease, new hospital treated illnesses etc. | Employment change: (new) involuntary job loss; planned normal retirement; early planned retirement; early ill-health retirement; re-employment |
2) Questionnaire: in those with MSDs: change in pain symptoms, SRH, CES-D, BSI, sleep problems | |
b) Effect of work on health: | |
Predictor variables | Outcome variables |
Employment status: unemployed, retired, ill-health retired, temporarily off sick, employed, other role (e.g., carer) | Change in health |
1) CPRD record: new diagnosis of, treatment for, worsening/recovery from … anxiety, depression, neurotic illness, insomnia, cardiovascular disease, hypertension; new hospital treated illnesses; altered frequency of GP visits | |
Employment change: (new) involuntary job loss; planned normal retirement; early planned retirement; early ill-health retirement; re-employment (Including MSD-related employment changes)
| |
2) Questionnaire: (change in) … SRH, CES-D, BSI, sleep problems |
Sample size and study power
Response patterns at baseline
Decile of deprivationa
| Practices (N) | Subjects | % of all participants | |||
---|---|---|---|---|---|---|
No. excluded | No. approached | No. recruited | % recruited | |||
1 (worst) | 2 | 77 | 2208 | 297 | 13.5 % | 3.6 % |
2 | 1 | 47 | 1830 | 322 | 17.6 % | 4.0 % |
3 | 0 | 0 | 0 | 0 | 0 % | 0 % |
4 | 1 | 66 | 1102 | 265 | 24.0 % | 3.3 % |
5 | 4 | 81 | 3944 | 673 | 17.1 % | 8.3 % |
6 | 5 | 389 | 11,940 | 2432 | 20.4 % | 29.9 % |
7 | 3 | 98 | 6080 | 1334 | 21.9 % | 16.4 % |
8 | 4 | 117 | 4761 | 1136 | 23.9 % | 14.0 % |
9 | 3 | 89 | 4879 | 1112 | 22.8 % | 13.7 % |
10 (best) | 1 | 33 | 2615 | 563 | 21.5 % | 6.9 % |
All | 24 | 997 | 39,359 | 8134 | 20.7 % | 100.0 % |
Location of practice | Practices (N) | Subjects | % of all participants | ||
---|---|---|---|---|---|
No. approached | No. recruited | % recruited | |||
London/South East | 3 | 3661 | 590 | 16.1 % | 7.2 % |
Central Southern | 2 | 3635 | 745 | 20.5 % | 9.2 % |
South West | 5 | 9003 | 1946 | 21.6 % | 24.0 % |
East | 4 | 8438 | 1854 | 22.0 % | 22.8 % |
West Midlands | 3 | 5843 | 1137 | 19.5 % | 14.0 % |
North East | 4 | 6165 | 1344 | 21.8 % | 16.5 % |
North West | 3 | 2614 | 518 | 19.8 % | 6.4 % |
All | 24 | 39,359 | 8134 | 20.7 % | (100.0 %) |
N (%) responded | % of all | ||
---|---|---|---|
Samplea
| Populationb
| ||
Date of birth (approx. age at baselinec) | |||
1948–1922 (60–64) | 3444 (28) | 42 | 30 |
1953–1957 (55–59) | 2582 (20) | 32 | 32 |
1958–1962 (50–54) | 2108 (14) | 26 | 37 |
(100) | (100) | ||
Sex: | |||
Male | 3707 (18) | 46 | 49 |
Female | 4427 (22) | 54 | 51 |
(100) | (100) |
Characteristic | Current work situation, N (%) | More than 1 current job, N (%) | |||
---|---|---|---|---|---|
Employed | Self-employed | Unemployed | Retired | ||
Sex: | |||||
Male | 2099 (56.6) | 593 (16.0) | 230 (6.2) | 785 (21.2) | 169 (4.6) |
Female | 2475 (55.9) | 342 (7.7) | 306 (6.9) | 1304 (29.5) | 252 (5.7) |
Age band (years):a
| |||||
50–54 | 1595 (75.7) | 258 (12.2) | 187 (8.9) | 68 (3.2) | 130 (6.2) |
55–59 | 1752 (67.9) | 322 (12.5) | 233 (9.0) | 275 (10.7) | 179 (6.9) |
60–64 | 1227 (35.6) | 355 (10.3) | 116 (3.4) | 1746 (50.7) | 112 (3.3) |
All: | 4574 (56.2) | 935 (11.5) | 536 (6.6) | 2089 (25.7) | 421 (5.2) |
Characteristic | Men N (%) | Women N (%) | All, N (%) |
---|---|---|---|
Ethnic group: | |||
Caucasian | 3627 (98.1) | 4334 (98.2) | 7961 (98.2) |
Other | 70 (1.9) | 78 (1.8) | 148 (1.8) |
Marital status: | |||
Married/civil partnership | 2728 (73.8) | 2995 (68.3) | 5723 (70.8) |
Widowed | 83 (2.3) | 242 (5.5) | 325 (4.0) |
Divorced | 472 (12.8) | 802 (18.3) | 1274 (15.8) |
Single | 414 (11.2) | 347 (7.9) | 761 (9.4) |
Educational qualification:a
| |||
None | 539 (14.5) | 733 (16.6) | 1272 (15.6) |
School | 631 (17.0) | 1014 (22.9) | 1645 (20.2) |
Vocational training certificate | 1203 (32.5) | 1246 (28.2) | 2449 (30.1) |
University degree | 631 (17.0) | 652 (14.7) | 1283 (15.8) |
Higher professional qualification | 703 (19.0) | 782 (17.7) | 1485 (18.3) |
Home ownership: | |||
Owned outright | 1849 (51.1) | 2442 (56.7) | 4291 (54.1) |
Owned with a mortgage | 1236 (34.2) | 1259 (29.2) | 2495 (31.5) |
Rented | 508 (14.0) | 584 (14.0) | 1092 (13.8) |
Living rent free | 26 (0.7) | 22 (0.5) | 48 (0.6) |
Living alone: | |||
Yes | 723 (19.8) | 974 (22.3) | 1697 (21.2) |
No | 2936 (80.2) | 3386 (77.7) | 6322 (78.8) |