It is common for people aged 65 and older to have multiple types of chronic diseases at the same time
However, a growing body of research has found that many chronic diseases are becoming younger and that developing chronic diseases at a young age may have an impact on future health management and the prevalence of other diseases
Dementia is a complex multisystem disease
Studies have found that it is common for older adults with dementia to have several chronic diseases at the same time
As scientists explore its pathophysiology, more and more attention has been paid to the relationship between various chronic diseases and Alzheimer's disease
Screenshot source: The BMJ
A large study published in The BMJ recently found that having two or more chronic diseases in midlife may be associated with an increased risk of dementia later in life
In this prospective cohort study, investigators included 10,095 participants with a baseline age of 35 to 55 years
The researchers then counted the probability of developing dementia among participants during the follow-up period, and used specific analyses to examine the relationship between chronic disease and subsequent dementia in these participants at age 55, 60, 65, and 70.
Common chronic diseases included in the study included 13 types including hypertension, diabetes, coronary heart disease, depression and chronic obstructive pulmonary disease (COPD)
After a median follow-up of 31.
7 years, the researchers found that the probability of having ≥2 chronic diseases at the age of 55 was 6.
6%, the probability of having ≥2 chronic diseases at the age of 70 was 31.
7%, and a total of 639 people had dementia
After adjusting for various confounding factors (such as age, sex, race, education, diet, and life>
This association diminishes with age when multiple chronic diseases develop
For example, people with ≥2 chronic diseases before age 55 had a 146% increased risk of dementia at age 65 (HR=2.
46), a difference of 3.
86/1000 person-years in incidence between the two groups
People with ≥2 chronic diseases between the ages of 60 and 65 had a 51% increased risk of dementia at age 65 (HR = 1.
51), with a difference in incidence between the two groups of 1.
Before age 70, the risk of developing dementia increased by 18% for every 5 years earlier in the age of onset
The researchers' analysis of more severe multi-morbidity (that is, having more chronic diseases at the same time) further underscores the association between younger age at onset and risk of developing dementia later in life
Having ≥3 chronic diseases at age 55 was associated with a 396% increased risk of developing dementia later in life (HR = 4.
96) compared with people with no chronic disease or one chronic disease, a difference of 5.
22/1000 - Years
The same analysis at age 70 showed a 65% increased risk of developing dementia at age 70 (HR = 1.
65), a difference in incidence between the two groups of 4.
The researchers point to limitations, such as the possibility that some cases of dementia patients may be misclassified, and that people in the study may be healthier than the general population
However, this was a large study with more than 30 years of follow-up, and further analysis using death as an outcome measure found similar results, adding to the researchers' confidence in that conclusion, the researchers said
The conclusion states that the onset of chronic disease in middle age is strongly associated with subsequent development of dementia
At present, the age of frequently-occurring diseases is getting younger and younger, and it is very important to prevent the occurrence of multiple chronic diseases in patients who have already developed the first chronic disease
 Hassen, CB, Fayosse, A.
, Landré, B.
, Raggi, M.
, Bloomberg, M.
, Sabia, S.
, & Singh-Manoux, A.
Association between age at onset of multimorbidity and incidence of dementia: 30 year follow-up in Whitehall II prospective cohort study.
 Midlife chronic conditions linked to increased dementia risk later in life.
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