Neurological conditions now leading cause of ill health and disability, study finds

Health loss from nervous system conditions affects 3.4 billion people globally, according to Lancet study

The prevalence of neurological disorders such as Alzheimer's has grown over the past three decades. Getty images

Neurological conditions are now the leading cause of ill health and disability affecting 3.4 billion people worldwide, a study has found.

Nervous system disorders – such as stroke, meningitis, Alzheimer's disease and other forms of dementia – have risen markedly over the past three decades, partially driven by ageing and lifestyle factors.

Researchers looked at the overall levels of disability, illness, and premature death caused by these conditions and measured them in what they described as disability-adjusted life years (Dalys).

They found Dalys had risen by 18 per cent in 30 years, rising from about 375 million years of healthy life lost in 1990 to 443 million in 2021.

The top 10 contributors to neurological health loss in 2021 were stroke, neonatal encephalopathy (brain injury), migraine, Alzheimer’s and other dementias, diabetic neuropathy (nerve damage), meningitis, epilepsy, neurological complications from preterm birth, autism spectrum disorder and nervous system cancers.

The neurological consequences of Covid-19, such as cognitive impairment from long Covid and Guillain-Barre syndrome, ranked 20th, accounting for 2.48 million years of healthy life lost in 2021.

The most prevalent neurological disorders in 2021 were tension-type headaches, with about 2 billion cases. Migraines accounted for 1.1 billion cases.

However, deaths from neurological conditions have declined by around a third worldwide since 1990, due largely to better awareness, vaccination and global prevention efforts.

Diabetic neuropathy, or nerve damage caused by diabetes, is the fastest-growing of all neurological conditions.

Scientists involved in the study say diabetic neuropathy has more than tripled globally since 1990, rising to 206 million in 2021. This is in line with the increase in the global prevalence of diabetes.

The researchers said that as many of these conditions lack cures, prevention needs to be a top priority.

According to the team’s analysis, modifying 18 risk factors over a person’s lifetime – most importantly high blood pressure – could prevent 84 per cent of global disabilities, illnesses, and premature deaths, from stroke.

Additionally, reducing high blood sugar levels to normal could reduce the burden of dementia by around 15 per cent, the researchers said.

Health loss from conditions such as tetanus (93 per cent decrease), meningitis (62 per cent decrease), and stroke (39 per cent decrease) have all reduced since 1990 when adjusted to take ageing populations into consideration.

Dr Tarun Dua, of the World Health Organisation’s Brain Health Unit, who co-authored the study, said this has disproportionately impacted the poorest countries, partly due to birth-related complications and infections affecting new-borns and young children.

Regions with the highest nervous system burden in 2021 were central and western sub-Saharan Africa, while high-income Asia Pacific and Australasia had the lowest.

“Every country now has estimates of their neurological burden based on the best available evidence,” said lead author Dr Jaimie Steinmetz from the Institute for Health Metrics and Evaluation.

“As the world’s leading cause of overall disease burden, and with case numbers rising 59 per cent globally since 1990, nervous system conditions must be addressed through effective, culturally acceptable and affordable prevention, treatment, rehabilitation and long-term care strategies.”

The findings were published in The Lancet Neurology journal.