The Malmö diet and cancer study: representativity, cancer incidence and mortality in participants and non-participants

Abstract

In order to investigate potential selection bias in population-based cohort studies, participants (n = 28098) and non-participants (n = 40807) in the Malmö Diet and Cancer Study (MDCS) were compared with regard to cancer incidence and mortality. MDCS participants were also compared with participants in a mailed health survey with regard to subjective health, socio-demographic characteristics and lifestyle. Cancer incidence prior to recruitment was lower in non-participants, Cox proportional hazards analysis yielded a relative risk (RR) with a 95% confidence interval of 0.95 (0.90-1.00), compared with participants. During recruitment, cancer incidence was higher in non-participants, RR: 1.08 (1.01-1.17). Mortality was higher in non-participants both during, 3.55 (3.13-4.03), and following the recruitment period, 2.21 (2.03-2.41). The proportion reporting good health was higher in the MDCS than in the mailed health survey (where 74.6% participated), but the socio-demographic structure was similar. We conclude that mortality is higher in non-participants than in participants during recruitment and follow-up. It is also suggested that non-participants may have a lower cancer incidence prior to recruitment but a higher incidence during the recruitment period.

Age at first childbirth and oral contraceptive use are associated with risk of androgen receptor-negative breast cancer: the Malmö Diet and Cancer Cohort

“…Some additional methodological concerns should be addressed. The participation rate in the MDCS was 40%, and a previous study on the background population has shown a selection of higher socioeconomic status in participants (35). The participating women in the MDCS were often postmenopausal; hence, the risk factors elucidated from this study may primarily cover postmenopausal breast cancer.…”

Can high psychological job demands, low decision latitude, and high job strain predict disability pensions? A 12-year follow-up of middle-aged Swedish workers

“…These people tend to be healthier than others (Manjer et al 2001). A comparison with a public health survey covering 74.6% of the same age cohort suggests that the MDCS population (see Methods), of which our population comprised a random sub-sample, was selected toward better health than the general population (Manjer et al 2001).…”

“…A comparison with a public health survey covering 74.6% of the same age cohort suggests that the MDCS population (see Methods), of which our population comprised a random sub-sample, was selected toward better health than the general population (Manjer et al 2001). Both these circumstances may have biased the estimated effects toward the null, but there may also be other effects of selection bias due to the participation rate of only 41%.…”

“…The subjects all resided in the city of Malmö (240,000 inhabitants) and were recruited into the larger Malmö Diet and Cancer Study (MDCS) (Manjer et al 2001) from February 1992to December 1994. The participation rate of the MDCS was 41%.…”

Conflict between the work and family domains and exhaustion among vocationally active men and women

“…In all, 40.8% of the eligible population completed the whole study which consisted of a baseline questionnaire (at T0) and anthropometric testing and blood samples. Comparison with a public health survey (Lindström, Bexell, Hanson, & Isacsson, 1995;Lindström, Sundquist, & Östergren, 2001), covering 74.6% of the same age cohort, suggests that the MDCS population sample was selected towards better health than in the general population (Manjer, Carlsson, Elmstahl, Gullberg, Janzon, Lindström et al, 2001).…”