The Dunedin Study - DMHDRU

What are our main findings so far?

Are brain-structure and walking speed related? We compared the speed at which people walk (measured on the long walkway upstairs) to several different measurements of the brain from the structural MRI scans. It turns out that there are slight structural brain differences, on average, between people with different walking speeds. (See publication)

Is “biological age” seen in the brain as well as the rest of the body? By comparing the structural MRI data with estimates of “biological age” (measured using 19 different things from heart to gum health) we showed that the brain structure and speed of aging of a person’s brain corresponds to their speed of aging in general, and to their rate of cognitive decline as they get older. (See publication 1 and publication 2)

What do spots (hyperintensities) in the MRI scans mean? We used one of the structural MRI scans to look for spots in the brain called White Matter Hyperintensities (WMHs). Accumulation of WMHs is a normal part of aging - virtually all Study members had some detected in their scans. We also found a statistical link between how many WMHs a person has and their rate of cognitive decline as they got older. (See publication) 

Is antisocial behaviour reflected in the brain? In two studies we used our data on antisocial behaviour going back to Study members’ teenage years to show that there are differences in average brain structure between people who have displayed antisocial behaviour (e.g., fighting, theft, property destruction) throughout their lives, those who only did so when they were teenagers/young adults, and those who have never engaged in any. (See publication 1 and publication 2)

Can a bigger brain explain higher IQ and education? By using a combination of the structural MRI scans and other data we showed that the link between IQ and level of education is partly related to brain size. (See publication) 

Is poor mental health seen in the brain? In two papers we used (click here for paper 1, paper 2) the structural scans to look at the relationship between mental health and brain structure. We found that differences in mental health between people (e.g., having one vs multiple mental health issues) were also reflected in differences in brain structure.  

Does cardiovascular fitness affect brain structure? We know that getting physical exercise is good for us in lots of different ways, including for our cardiovascular system.  But what about for our brains?  We found that cardiovascular fitness does seem to be linked to brain structure, and that cardiovascular fitness may in fact influence brain structure.  (See publication 1 and publication 2 )

What effect does lead have on the brain?  When the Study members were children petrol still contained lead. So we wondered what effect childhood exposure to lead had on the brain at age 45.  By using Study members’ childhood data we found that the amount of lead in the blood during childhood is connected to both grey- and white-matter brain structure. (See publication) 

Do difficult childhoods affect the brain?  We were able to use the structural MRI data and our data from Study members’ childhoods to show that, on average, people who had experienced childhood adversity such as abuse or severe family problems have slightly different brain structure to those who didn’t experience those things.  However we do not know yet whether childhood difficulties and brain differences are causally related or whether there is some other common factor that connects them. (See publication)

Is adult brain structure related to childhood self-control?   “Self-control” (the ability to control your own behavior and emotions) during childhood is linked to things in later life such as financial well-being and health.  So we wondered whether there might also be a relationship between self-control in childhood and brain structure in middle-age.  We found that Study members who had better childhood self-control tended to also have younger-looking brains and fewer White-Matter Hyperintensities (see findings 2 and 3 above).  However it may be that this is explained by differences between people in childhood IQ and social class. (See publication)

Do we have any advice for other MRI researchers? The papers described so far have all used the MRI data to study the relationship between people’s brains and other aspects of their health and lives. But in two of the papers we took a different approach and used the MRI data to try to improve the way in which MRI research is done. The first paper used both the resting-state scan (the fMRI scan that measured brain activity when your brain was not concentrating on doing something) and the fMRI scans done while you played the games. We found that combining these different data sets gave a better way to measure networks in the brain (in which different parts of the brain become active at the same time) than normally used by researchers. The second paper used the data from the fMRI game scans to show that when a small number of Study members were scanned a second time (see question 10) the fMRI data were not as consistent with their first scan as we had expected. These are both important findings for how we and other researchers will use fMRI scans in the future.

Is there a relationship between adolescent health and brain-aging? By using the MRI scans, and data on smoking, mental health problems, and obesity, from Study members’ teenage years, we showed that experiencing these things during adolescence made it more likely that the brain would show signs of faster aging . (See publication).

Does cannabis affect brain structure? We have previously shown that long-term cannabis use is linked to a decrease in IQ, so we wondered whether this could also be seen in brain structure. Comparing cannabis-use data to the MRI scans appeared to show that people who used cannabis throughout their adult lives had, on average, brains that had different structure and showed signs of faster aging compared to the brains of non-users and occasional users. However, we also showed that these apparent differences were not actually due to cannabis but instead were related to the fact that long-term cannabis users also tended to be long-term smokers and alcohol users. (See publication)

Is brain-aging related to chronic inflammation? Comparing the MRI scans to data obtained from Study members’ blood samples allowed us to show that people who have higher levels of chronic inflammation in their bodies also had brains that appear to be aging faster. (See publication)

How well can Alzheimer’s disease be predicted using Dunedin Study data? To work out someone’s future risk of dementia such as Alzheimer’s disease, doctors have to rely on methods that use information from simple tests or questionnaires. We wondered whether these methods could be improved so we used Study member information collected over the years to try to better assess dementia risk. Of course we can’t see decades into the future, but we could use the MRI data as a reasonable substitute because people with older looking brains in mid-life are more likely to experience dementia in old age. As it turns out, existing clinical methods of measuring dementia risk actually do almost as well as we could, however we showed that they could be further improved by adding in extra bits of easily obtained information. (See publication)


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