Dr. Ramit Ravona-Springer of Sheba Medical Center, Tel Hashomer, Israel, and colleagues said the tendency for rumination was assessed in about 9,000 participants in a longitudinal study of the incidence and risk factors for cardiovascular disease among Jewish male civil servants in Israel.

The prevalence rates of dementia -- adjusted for age, area of birth and socioeconomic status -- were 21 percent for those who always forget difficulties in familial settings, 18 percent for those who tend to forget, 14 percent for those who tend to ruminate over difficulties and 14 percent for those who usually ruminate. When rumination in response to difficulties at work was assessed, prevalence rates of dementia were 24 percent for those who always forget difficulties, 19 percent for those who tend to forget, 15 percent for those who tend to ruminate over difficulties and 15 percent for those who usually ruminate.

Relative to the group with the lowest total rumination score, dementia prevalence was 30 percent to 40 percent less in groups with higher scores.

The study was presented at the Alzheimer's Association International Conference on Alzheimer's Disease in Chicago.