Appendix 1: [As supplied by authors] Overview of the dates defining analyse periods for the age cohorts. Shaded areas indicate invitation of both invited and control group.

		Period 1 (Screening only of invited group)		Period 2 (No screening or screening of both invited and control group)
Birth cohort	Mean age at randomisation	Start	End	Start	End
1908	69.9	May 1978	1986^�	1987	2001
1909	68.8	April 1978	1986^�	1987	2001
1910	67.7	March 1978	1986^�	1987	2001
1911	66.7	March 1978	1986^�	1987	2001
1912	65.6	February 1978	1986^�	1987	2001
1913	64.6	January 1978	1986^�	1987	2001
1914	63.5	December 1977	1986^�	1987	2001
1915	62.3	November 1977	1986^�	1987	2001
1916	61.4	November 1977	1986^�	1987	2001
1917	59.7	March 1977	1986^�	1987	2001
1918	58.8	April 1977	Until age 70	From age 71	2001
1919	57.9	June 1977	Until age 70	From age 71	2001
1920	57.2	August 1977	Until age 70	From age 71	2001
1921	55.3	October 1976	Until age 70	From age 71	2001
1922	55.2	September 1977	Until age 70	From age 71	2001
1923	54.3	October 1977	�	December 1991*	2001
1924	52.9	May 1977	�	December 1991*	2001
1925	51.9	June 1977	�	December 1991*	2001
1926	50.6	February 1977	�	Sept 1990/Dec 1991**	2001
1927	49.7	February 1977	�	March 1992*	2001
1928	49.9	May 1978	�	March 1992*	2001
1929	48.3	October 1977	�	May 1992*	2001
1930	48.0	June 1978	�	May 1992*	2001
1931	47.1	August 1978	�	January 1993*	2001
1932	46.2	August 1978	�	February 1993*	2001

^{� End of the trial December 31, 1986.
� Up to the date for the start of the screening of the control group.
* Average start date for the invitation on the control group.
** Women born first half of the year were invited in the first period, and second half in the second period due to administrative reasons when the screening program started.}