Scientists from the Uniformed Services University (USU), Emory University and the University of Vermont have found that cigarette smoking is linked to increased lesions in the brain’s white matter, called white matter hyperintensities. White matter hyperintensities, detected by MRI scan, are associated with cognitive decline and Alzheimer’s disease. These findings may help explain the link between smoking and increased rates of dementia and other forms of cognitive decline.
The study, “Associations of cigarette smoking with gray and white matter in the UK Biobank” was published online in the journal, Neuropsychopharmacology, https://rdcu.be/b1jPS
In June 2019, the Surgeons General of the Army, Navy, Air Force, and United States, released an open letter stating that tobacco use is a threat to the health and fitness of U.S. military forces and compromises readiness. This burden also extends to care provided by the Veterans Health Administration, which spends more than $2.5 billion annually on smoking-related care. In response, Dr. Joshua Gray, assistant professor of Medical and Clinical Psychology and Neuroscience at USU, and colleagues, examined the association between cigarette smoking and brain structure. Cigarette smoking is associated with increased risk for myriad health consequences including increased risk for neuropsychiatric conditions, but research on the link between smoking and brain structure is limited.
Their study was the largest of its kind, including MRI brain scans from more than 17,000 individuals from the UK Biobank, a large cohort of volunteers from across the United Kingdom. They found that smoking was associated with smaller total gray and white matter volume, increased white matter lesions, and variation in specific gray matter regions and white matter tracts. By controlling for important variables that often co-occur with smoking, such as alcohol use, this study identified distinct associations between smoking and brain structure, highlighting potential mechanisms of risk for common neuropsychiatric consequences of smoking such as depression and dementia.
“Cigarette smoking is known to elevate risk for neuropsychiatric conditions such as depression and dementia. We found that smoking is associated with multiple aspects of brain structure, in particular with increased white matter lesions. White matter lesions are linked to many of the same neuropsychiatric diseases as smoking,” said Gray. “Although further research is needed to understand to what extent smoking is a cause or consequence of these aspects of brain structure, our findings suggest a mechanism that links smoking to increased risk for dementia, depression, and other brain diseases.”
Brain Enlargement in Autism Due to Brain Changes Occurring Before Age 2
CHAPEL HILL, N.C. – In 2005, researchers from the University of North Carolina at Chapel Hill found that 2-year-old children with autism have brains up to 10 percent larger than children of the same age without autism.
Now a follow-up study by UNC researchers has found that the children who had enlarged brains at age 2 continued to have enlarged brains at ages 4 and 5, but the amount of the enlargement was to the same degree found at age 2. This increased brain growth did not continue beyond 2 years of age and the changes detected at age 2 were due to overgrowth prior to that time point. In addition, the study found that the cortical enlargement was associated with increased folding on the surface of the brain (or increased surface area) and not an increase in the thickness of outer layer of the brain (or gray matter).
“Brain enlargement resulting from increased folding on the surface of the brain is most likely genetic in origin and a result of an increase in the proliferation of neurons in the developing brain,” said Heather Cody Hazlett, PhD, assistant professor in the Department of Psychiatry, who is the lead author of the new study, which is published in the May 2011 issue of Archives of General Psychiatry.
In both the 2005 study and the new study, Hazlett and colleagues analyzed magnetic resonance imaging (MRI) scans of the children’s brains using computer software developed for that purpose by Martin Styner, PhD, an assistant professor of computer science and psychiatry at UNC, and Guido Gerig, PhD, formerly at UNC and now at the University of Utah.
“From earlier work by our group on head circumference or head size in children with autism, we think that brain overgrowth in many children with autism may actually be happening around the first birthday. Together these findings suggest that we should be searching for genes that may underlie the over-proliferation of neurons in this early post-natal period,” said Joseph Piven, MD, senior author of the new study and director of the Carolina Institute for Developmental Disabilities.
UNC is currently leading two separate studies aimed at that goal. Hazlett leads the Brain Development in School Age Children with Autism study, which is funded by Autism Speaks. “It was important to continue to follow these children to track their brain development to see if the brain and behavioral differences we observed were maintained as the children matured,” said Hazlett.
UNC is also leading the Infant Brain Imaging Study (IBIS), a National Institutes of Health-funded multi-center study which includes four sites around the U.S. “We are studying infant children at high genetic risk for autism, by virtue of their having an older brother or sister with autism – somewhere around 20 percent of those children will develop autism. We are doing brain scans and behavior assessments on those children at 6, 12 and 24 months of age to look at how the brain develops in the subgroup that develop autism before they have symptoms of autism at 6 months of age and over the interval that they develop autism – between 6 and 24 months of age, in most cases,” Piven said. “We are also looking at whether specific gene alterations may be responsible.”
Authors of the May 2011 article in Archives of General Psychiatry, in addition to Hazlett, are Michele Poe, PhD, Guido Gerig, PhD, Martin Styner, PhD, Chad Chappell, Rachel Gimpel Smith, Clement Vachet, MS, and Piven.
The UNC authors are all affiliated with one or more of the following: The Department of Psychiatry in the School of Medicine, the Carolina Institute for Developmental Disabilities, the Frank Porter Graham Child Development Institute, and the Department of Computer Science in the College of Arts and Sciences.