Table 1.
Details of the two Hertfordshire birth cohorts, data collection and participants
| Cohort | Data collection | Number invited |
Number interviewed (% of invited) |
Number (% of invited) with blood pressure data |
Number (% of invited) with CHD data |
|---|---|---|---|---|---|
| Hertfordshire cohort born 1920–30a |
1989–91 (East Herts) | 1722 | 1233 (72) | 1231 (71) | – |
| 1992–93 (East Herts) | 655 | 515 (79) | – | 502 (77) | |
| 1993–94 (North West Herts) | 1015 | 586 (58) | 585 (58) | 586 (58) | |
| 1994–95 (North Herts) | 1428 | 824 (58) | 819 (57) | 306 (47) | |
| Hertfordshire cohort born 1931–39 (‘Hertfordshire Cohort Study’) |
1998–2004 | 6099 | 3225 (53) | 2986 (49) | 2957 (48) |
In contrast to the Hertfordshire Cohort Study, data collection on the first Hertfordshire birth cohort was conducted as a series of studies. We therefore describe these component studies separately. Two studies were carried out in East Herts; blood pressure data from the initial study is used in these analyses. In the repeat study, only those men and women who had complete measurements on all blood samples taken in the initial study were invited to attend clinic for assessment of coronary heart disease. In the North Herts study, while data on blood pressure are available for both men and women, only women had full assessment of coronary heart disease at clinic; number (% invited) with CHD data therefore refers to women only.