In a new study, researchers found over the past 20 years or so, the risk for US men and women suffering from cognitive impairment and dementia has increased.
The burden might be heavier than long assumed: For years, most studies using survey data suggested that the risk of suffering from cognitive impairment is declining in high-income countries.
They often use longitudinal surveys in which the same individuals take the same test over and over. This results in learning, which if not taken into account, may bias results.
The research was conducted by a team at the Max Planck Institute for Demographic Research (MPIDR) and elsewhere.
In the study, the team used data from more than 32,000 participants from the Health and Retirement Study (HRS). That is a nationally representative, biennial panel survey of US residents age 50 and older and their spouses.
They analyzed the prevalence of cognitive impairment in the United States from 1996 to 2014 taking into account testing experience and selective mortality.
Results based on models that do not control for test experience suggest that the risk of cognitive impairment and dementia decreases over the study period.
However, when the team controlled for testing experience in the model the trend reverses.
In their models, the prevalence of any cognitive impairment increases for both women and men.
The increase was particularly strong among Latinas, the least educated, and people over 85. Some of the increase may be driven by people living longer with dementia.
One author of the study is Mikko Myrskylä.
The study is published in the journal Epidemiology.
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