According to the team, led by Mary Haan, DrPH, after 10 years of follow-up they discovered that, after accounting for the competing risk of death and other factors, patients under treatment for diabetes had double the risk of developing dementia or other cognitive impairment. There was a similar trend seen with untreated diabetics, but this relationship was not statistically significant.
In their report, published online in Diabetes Care, the researchers wrote, ‘Screening and treatment for diabetes that changes survival among those with type 2 diabetes may influence future dementia incidence rates.’ They noted that mortality rates among patients with diabetes have declined in recent years, and so ‘the potential impact … will depend on the factors causing the decline in the mortality rate.’
They added that if earlier screening and better management of the disease are responsible for the decline in the mortality rate, then the dementia rates may also decline. Yet, if the decline in mortality rates have not resulted from a reduced severity of the disease, ‘and if more severe diabetes influences dementia risk … dementia rates among people with diabetes could potentially increase,’ they said.
For their study, the investigators used data from the Sacramento Area Latino Study on Ageing, in order to explore the relationship between type 2 diabetes and dementia and other cognitive impairments among Mexican Americans. This is the first study to explore the relationship in Latinos, who have high rates of diabetes, poor glycaemic control, and more complications compared with non-Hispanic whites.
Of the 1,617 participants, 41.9% had diabetes at baseline or developed it during follow-up, 9.8% developed dementia or cognitive impairment during the study, and 22.3% died. Both treated and untreated diabetes were associated with risk of developing dementia and other cognitive impairment (HRs 2.38 and 1.88, respectively). The authors noted, ‘Those with treated diabetes in our sample have higher glucose and insulin, [a higher rate of] hypertension, and more comorbid cardiovascular disease, and may have more severe diabetes than those who were untreated. This may explain why their dementia risk is higher, given that the risk of death is similar in both groups.’