Inflammation has been associated with Alzheimer's disease (AD) and dementia. The association between rheumatoid arthritis (RA) or arthritis and dementia/AD has been investigated in several case-control or hospital- and register-based studies with mixed results. This long-term population-based study investigates the association between presence of joint disorders (RA and other joint disorders) in midlife and cognitive status later in life. 1,449 participants were first evaluated in 1972, 1977, 1982, and 1987 and follow-up was performed after 21 years. A self-administered questionnaire including questions on joint disorders was used at both evaluations. Cognitive status (control, mild cognitive impairment, dementia/AD) was assessed at follow-up. The presence of any joint disorder in midlife was significantly associated with a worse cognitive status later in life: OR (95% CI) in an ordinal logistic regression analysis adjusted for age, gender, follow-up time, education, APOEε4, body mass index, smoking, drug treatment, and diabetes was 1.96 (1.17-3.28). For RA only, OR (95% CI) was 2.77 (1.26-6.10). The correlation remained significant for RA when AD was considered instead of dementia OR (95% CI) 2.49 (1.09-5.67). The presence of joint disorders, especially RA, at midlife seems to be associated with a worse cognitive status later in life. Given the chronic inflammatory component of RA, this study suggests that inflammatory mechanisms may have an important role in increasing the risk of cognitive impairment and dementia/AD.