<i>Aims:</i> The study aimed to estimate incidence rates of mild cognitive impairment and related disorders, and conversion to dementia. <i>Methods:</i> The data are drawn from the PATH Through Life Study. Baseline assessment in 2001–2002 included 2,551 participants 60–64 years old with 2,222 participating in a 4-year follow-up. Those screened positive with a cognitive assessment received clinical assessment for diagnoses of mild cognitive disorders (MCD) or dementia using established clinical criteria. Prevalence and incidence rates for the cohort were estimated with predictive regression models. <i>Results:</i> Annual incidence of dementia was 0.25%. Prevalence of mild cognitive impairment was 4.2%, age-associated memory impairment was 2.4%, age-associated cognitive decline was 7.6%, mild neurocognitive disorders occurred in 12.9% and other cognitive disorders in 7.3%. Prevalence of any diagnosis of any MCD (Any-MCD) was 29.5% and the annual incidence rate for Any-MCD was 5.7%. Agreement for specific diagnoses between waves 1 and 2 was fair to poor (0–47.0%), but agreement for Any-MCD over 4 years was 89.0%. <i>Conclusion:</i> MCD diagnoses do not predict dementia at a 4-year follow-up in young-old adults. Prevalence rates for MCD vary greatly depending on the criteria and time of assessment.