handcuffs, arrest, criminal
The draft guidelines for the national sex offender's list proposes names of convicts of all kinds of sexual offences to be on the list. Picture: A man's hands shown in cuffs.Victor/Flickr

A tendency to exhibit criminal behaviour at old age may be indirectly signalling any hidden neurodegenerative disease like Dementia, latest research shows.

When a neurodegenerative disease strikes a person, certain neural structures that manage judgement, sexual behaviour, violence, executive function, emotional processing and self-awareness get badly affected or damaged, which further make him or her display antisocial and criminal behaviour, according to researchers from Lund University in Sweden and University of California, San Francisco in US.

For the study, researchers Madeleine Liljegren and Georges Naasan looked at 2,397 patients in the University of California, San Francisco, Memory and Aging Center.

Participants suffered from different types of neurodegenerative diseases including Alzheimer disease or AD (545), behavioral variant of frontotemporal dementia (bvFTD-171), primary progressive aphasia (PPA), a language disorder (89) and Huntington disease (30).

Data showed that 8.5% (204) of the patients exhibited criminal behaviour at the time of their disease. The link was stronger in dementia patients (37.4%) than people with AD (7.7%), language disorder (27%) or Huntington disease (20%).

The common criminal and antisocial behaviours among the bvFTD group included traffic violations, sexual advances, public urination, trespassing and theft.

"Criminal behavior is more common in patients with bvFTD and semantic variant of primary progressive aphasia than in those with AD and is more likely to be an early manifestation of the disorder," the authors while concluding their study wrote.

"Judicial evaluations of criminality in the demented individual might require different criteria than the classic "insanity defense" used in the American legal system; these individuals should be treated differently by the law. The appearance of new-onset criminal behavior in an adult should elicit a search for frontal and anterior temporal brain disease and for dementing disorders."

Findings of the study, published in the online issue of JAMA Neurology, are believed to help improve diagnosis of dementia, a syndrome related to the brain that leads to memory loss, difficulties in communicating, thinking, planning and performing daily routines.

Nearly 35.6 million people in the world have dementia, according to the World Health Organisation (WHO).