The Malmö Diet and Cancer Study: representativity, cancer incidence and mortality in participants and non-participants

Eur J Cancer Prev. 2001 Dec;10(6):489-99. doi: 10.1097/00008469-200112000-00003.


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.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Cause of Death
  • Diet
  • Female
  • Follow-Up Studies
  • Health Status
  • Health Surveys
  • Humans
  • Incidence
  • Male
  • Middle Aged
  • Mortality*
  • Neoplasms / epidemiology*
  • Patient Selection
  • Proportional Hazards Models
  • Prospective Studies
  • Selection Bias
  • Socioeconomic Factors
  • Sweden / epidemiology