b'Change over TimeCognition can also change over time, and that is why HRS asks the same questions again and again over the years. Understanding how our brains change is an important part of helping slow or prevent cognitive decline. When we combine all of our answers together, we can see important trends in the population.The graph below shows that the rate of dementia (prevalence) in the population is actually decreasing over time and in younger cohorts. These positive trends are due to things like education and better treatment for conditions like high blood pressure and diabetes that affect dementia risk. But the rapid growth of our older population means that the burden of Alzheimers disease will grow even if the recent trends toward lower rates of the disease continue. The HRS will continue to play a major role in tracking dementia trends to measure the full impact of dementia on society as the number of older adults who are at highest risk for dementia increases in the decades ahead.TakeawayPrevalence of Dementia by Age from 19982016n 85+n 75-84n 65-74 Prevalence decreased from 1998 to 201685+ years: 4.6%75-84 years: 4.8%65-74 years: 1.4%Source: HRS, 199820165'