A new longitudinal study that analyzed data from hundreds of thousands of men found a connection between height and probability of dementia developing.
According to statistics from the World Health Organization (WHO), dementia— an umbrella term that includes multiple cognitive impairment disorders, the most common of which is Alzheimer’s — affects about 50 million people worldwide.
There is currently no cure for dementia, so researchers are keen to recognize the many potential risk factors to promote early diagnosis and intervention.
Now, a new study by the University of Copenhagen in Denmark has found an correlation that hadn’t been much discussed before: a link between height and risk of dementia.
The study— led by assistant professor Terese Sara Høj Jørgensen— was spurred on by suggestions from previous studies that height could correlate with brain health risks.
Jørgensen and the team have obtained height and possible dementia diagnosis data through conscription records and national registries. Our findings have now been published in the journal eLife.
“We wanted to see if body height in young men is correlated with dementia diagnosis while investigating whether the association is clarified by intelligence test scores, educational level and underlying environmental and genetic factors shared by brothers,” Jørgensen states.
Height may be relevant to dementia risk
The researchers examined data from people who were born between 1939 and 1959. There were 666,333 individuals in their cohort, 70,608 of whom were Nontwin brothers and 7,388 were Twins.
The men in this cohort had taken conscript board exams from 1957 to 1984, and they had been clinically followed up by national registries until 2016.
By analyzing data from those sources, the researchers found that at some point 10,599 of the 666,333 men developed a form of dementia.
Researchers noted that there appeared to be a correlation between a man’s height and his risk of dementia— specifically, men who were taller than average appeared to have a lower risk of dementia than men who were lower than average.
Therefore, if the mean height for men born in 1939 was 1.75 meters, over the mean height for about every 6 centimeters, the risk of dementia was decreased by about 10 percent.
The researchers adjusted their study for potential confounding factors, including rates of education and scores of the intelligence test. The link between height and dementia risk was reduced when they did so — but not dramatically.
The researchers found that the relation between height and dementia risk was present in brothers with different heights when they compared results among siblings.
The relationship has also been present in twins, although the team admits that the results in this context were less conclusive.
Environmental factors may be at the root
Jørgensen and her colleagues note that looking at the results, it seems unlikely that the genetic makeup of a individual alone will explain the link between the risk of height and dementia.
Alternatively, they suggest that height— especially short stature — can represent early-life environmental conditions that could be the true risk factors for dementia.
“Our study’s key strength is that it has been tailored for the potential role of education and intelligence in the risk of dementia among young men, both of which can build up cognitive reserves and make this community less vulnerable to dementia,” states senior author Prof. Merete Osler.
“After this adjustment, our results still point to an association between taller body height in young men and a lower risk of dementia diagnosis later in life. Our analysis of brothers further suggests that the association may have common roots in early-life environmental exposures, unrelated to family factors shared by brothers.”
– Prof. Merete Osler
More longitudinal research, the researchers suggest investigating the connection with environmental exposures in greater depth.
They also warn that their results may not be specific to women. Certain studies, they claim, ought to establish whether biological sex plays a role in the height-to-dementia risk link.
