Background Although the relation between low income and poor health is well established, most previous research has measured income at only one time.

Methods We used income information collected in 1965,1974, and 1983 from a representative sample of adults in Alameda County, California, to examine the cumulative effect of economic hardship (defined as a total household income of less than 200 percent of the federal poverty level) on participants who were alive in 1994.

Results Because of missing information, analyses were based on between 1081 and 1124 participants (median age, 65 years in 1994).

After adjustment for age and sex, there were significant graded associations between the number of times income was less than 200 percent of the poverty level (range, 0 to 3) and all measures of functioning examined except social isolation.

As compared with subjects without economic hardship, those with economic hardship in 1965,1974, and 1983 were much more likely to have difficulties with independent activities of daily living (such as cooking, shopping, and managing money) (odds ratio, 3.38 ; 95 percent confidence interval, 1.49 to 7.64), activities of daily living (such as walking, eating, dressing, and using the toilet) (odds ratio, 3.79 ; 95 percent confidence interval, 1.32 to 9.81), and clinical depression (odds ratio, 3.24 ; 95 percent confidence interval, 1.32 to 7.89) in 1994. (...)