Neurologic Conditions Now Leading Cause of Disability Worldwide

Disorders affecting the nervous system were the leading cause of ill health and disability globally, affecting 3.4 billion people worldwide, a systematic analysis for the Global Burden of Disease (GBD) Study showed.

Neurologic conditions affected 43.1% of the world’s population and were the top contributor to the global disease burden in 2021, ahead of cardiovascular diseases (excluding stroke), according to Jaimie Steinmetz, PhD, MSc, of the Institute for Health Metrics and Evaluation at the University of Washington in Seattle, and co-authors.

Globally, 37 conditions affecting the nervous system were responsible for 443 million disability-adjusted life-years (DALYs) and 11.1 million deaths in 2021, Steinmetz and colleagues reported in Lancet Neurology.

The analysis spanned data from 1990 to 2021. Overall, global DALYs increased by 18.2% from 375 million in 1990, but age-standardized rates of DALYs and rates of death per 100,000 people decreased by 27% and 33.6%, respectively.

The ten conditions with the highest age-standardized DALYs worldwide were stroke, neonatal encephalopathy, migraine, Alzheimer’s disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurologic complications due to preterm birth, autism spectrum disorder, and nervous system cancer.

Previous GBD studies estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders or a subset of cases of congenital, neonatal, and infectious conditions that cause nervous system damage, the researchers noted. Collectively, neurodevelopmental and pediatric conditions accounted for 18.2% of the total neurologic burden worldwide, equivalent to 80.3 million DALYs in 2021.

“The burden of neurological conditions has increased over the past three decades,” Steinmetz observed. “Given that many of the conditions included in our analysis do not have cures, prevention by addressing modifiable risk factors is key,” she told MedPage Today.

“In our analysis, we highlighted risk factors already examined in the Global Burden of Disease Study, including 18 risk factors for stroke, with the largest burden attribution for high systolic blood pressure. Stroke is the top global contributor to neurological health loss, so targeting hypertension and its other risk factors should be a priority,” Steinmetz noted.

“In general, we need to assess as many risk factors as possible across the different neurological conditions so intervention programs can target risk factors that have the greatest contribution to disease burden,” she said.

The GBD study team estimated mortality, prevalence, years lived with disability, years of life lost, and DALYs by age and sex in 204 countries and territories, from 1990 to 2021. They included morbidity and deaths due to neurologic conditions in which health loss was directly due to damage to the central nervous system or peripheral nervous system.

The researchers also isolated neurologic health loss from conditions for which nervous system morbidity was a consequence but not the primary feature, including a subset of congenital conditions (chromosomal anomalies and congenital birth defects); neonatal conditions like jaundice, preterm birth, and sepsis; infectious diseases like COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease; and diabetic neuropathy. To ensure only cases in which nervous system damage occurred were included, they conducted a sequela-level analysis of health outcomes.

The fastest-growing condition was diabetic neuropathy, which mirrored the global rise in diabetes. Neurologic consequences of COVID-19 included cognitive impairment and Guillain-Barré syndrome and accounted for 2.48 million aged-standardized DALYs in 2021, ranking 20th on the list.

“This important new GBD report highlights that the burden of neurological conditions is greater than previously thought,” noted Wolfgang Grisold, MD, president of the World Federation of Neurology in London, England, in an accompanying editorial.

“In the next iteration, more attention should be given to neuromuscular diseases, the effects of cancer in the nervous system, and neuropathic pain,” Grisold wrote. “Comparing the disability caused by conditions with episodic occurrence versus those that cause permanent and progressive disease will remain challenging, because the effects on the individuals vary substantially.”

A previous report from GBD researchers reviewed the burden of neurologic disorders across the U.S. from 1990 to 2017. An update is expected, but nothing is pending immediately, Steinmetz said.

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