Table 2.
Annual primary care costs (£) models: Generalised linear models with Poisson distribution and identity link function
| Covariate | Participants without previous CVD | Participants with previous CVD |
|---|---|---|
| Mean (SE) a | Mean (SE) a | |
| Intercept | 262 (4) | 302 (22) |
| Baseline characteristics | ||
| Male (ref: female) | − 51 (3) | − 50 (13) |
| Ethnicity (ref: white) | ||
| Black | − 3 (11) | 61 (127) |
| South Asian | 57 (9) | 24 (36) |
| Others* | − 3 (2) | − 107 (24) |
| Townsend socioeconomic deprivation (ref: Quintile 3) | ||
| Quintile 1 (least deprived) | − 5 (1) | 6 (17) |
| Quintile 2 | 4 (2) | 25 (17) |
| Quintile 4 | 6 (3) | 49 (21) |
| Quintile 5 | 50 (6) | 132 (34) |
| Smoking (ref: never) | ||
| Former smoker | 22 (2) | b |
| Current smoker | 50 (5) | b |
| Physical activity (ref: moderate) | ||
| Low | 30 (5) | 117 (21) |
| High | − 2 (2) | − 8 (10) |
| Missing | 32 (4) | 96 (21) |
| BMI (ref: ≥ 18.5, < 25) | ||
| < 18.5 | 36 (15) | 182 (107) |
| ≥ 25, < 30 | 3 (2) | 8 (11) |
| ≥ 30, < 35 | 31 (4) | 58 (16) |
| ≥ 35, < 40 | 91 (9) | 194 (46) |
| ≥ 40 | 132 (13) | 329 (44) |
| LDL cholesterol (centred at 3.6; per 1 mmol/L) | − 6 (2) | b |
| Natural logarithm of HDL cholesterol (lnmmol/L) | − 32 (6) | b |
| Systolic blood pressure (centred at 140; per 20 mmHg) | b | − 20 (6) |
| On antihypertensive treatment (ref: no) | 127 (5) | 93 (14) |
| Severe mental illness history (ref: no) | 152 (6) | 280 (31) |
| Prior type 1 diabetes (ref: no) | 643 (45) | 731 (78) |
| Prior CVD (ref: MI only) | ||
| PAD only | NA | 66 (19) |
| Stroke only | NA | 124 (37) |
| Other CHD only^ | NA | 84 (17) |
| Two or more | NA | 221 (22) |
| Time-updated characteristics | ||
| Current age (centred at 60; per 10 years) | 57 (2) | 62 (7) |
| Incident MI (ref: no) | 194 (24) | 231 (54) |
| Incident stroke (ref: no) | 362 (56) | 428 (82) |
| Incident CRV (ref: no) | ||
| Same year | 391 (40) | 233 (33) |
| ≥ 1 year ago | 69 (15) | 10 (26) |
| Diabetes (ref: no) | ||
| < 10 years ago | 360 (11) | 343 (24) |
| ≥ 10 years ago | 560 (19) | 568 (39) |
| Cancer (ref: no) | ||
| < 5 years | 357 (11) | 236 (25) |
| ≥ 5, < 10 years | 159 (13) | 123 (28) |
| ≥ 10 years ago | 77 (6) | c |
| VD (ref = no) | − 95 (30) | − 16 (91) |
| NVD (ref = no) | 389 (37) | 198 (65) |
| Interactions | ||
| Any incident MI and same year CRV (ref = no) | − 226 (47) | b |
| Any incident MI and same year VD (ref = no) | b | − 500 (109) |
| Any incident stroke and same year VD (ref = no) | − 277 (86) | − 439 (133) |
| < 5 years cancer and same year NVD (ref = no) | − 245 (47) | b |
Costs in years with administrative censoring at end of study follow-up were adjusted by including a further covariate of proportion of year not observed (not shown)
For an example of how to use this model, see Supplement section 8 of Online Resource 1 in the electronic supplementary material
BMI body mass index, CHD coronary heart disease, CRV coronary revascularization, CVD cardiovascular disease, HDL high density lipoprotein, LDL low density lipoprotein, MI myocardial infarction, NA not applicable, NVD non-vascular death, PAD peripheral arterial disease, SE standard error, VD vascular death
*Other ethnicity includes Chinese, Mixed, White and Black Caribbean, White and Black African, White and Asian, any other mixed background and other ethnic group
^Other CHD includes acute rheumatic fever, chronic rheumatic heart diseases, hypertensive heart disease, angina pectoris, other acute ischaemic heart disease, chronic ischaemic heart disease, pulmonary heart disease and other form of heart disease
aThe interpretation and use of model coefficients is as for any linear regression model. The intercept represents the annual cost for an individual in the reference categories of all covariates. All other coefficients represent the additional annual costs for an individual in the respective category compared with the reference category
bCovariate or interaction term excluded during the selection procedure (not statistically significant)
cSame as the preceding temporal category