Trends in Cause-Specific Mortality by Race and Hispanic Origin, 1999–2019

Diseases of the Nervous System

The proportions of all deaths that were caused by diseases of the nervous system in 2019 ranged from 5.6 percent among Black individuals to 8.8 percent in the WNH population. The share of deaths attributed to this category of causes rose significantly over the observation period and was typically higher among women than men. This section examines mortality from the eight nervous system disease subcategories listed in Box 6.

Chart 23 shows the number and percentage distribution of nervous system disease–related deaths by cause-of-death subcategory for 1999 and 2019, with detail by RE group and age. By far, Alzheimer's disease was the primary cause of death at all ages among the disorders of the nervous system, accounting in 2019 for 47.4 percent of such deaths among the Black population and more than half of them in all other RE groups. The percentages are significantly higher among women than men (consistent with Viña and Lloret 2010) and at older ages than younger ones. For instance, the shares of nervous system disease–related deaths attributed to Alzheimer's disease at ages 65 or older among WNH men and women were 44.4 percent and 63.5 percent, respectively.

Chart 24 shows age-adjusted death rates for 1999–2019 by RE group, sex, and age group. Panel A shows the rates for nervous system diseases overall.

Chart 24, Panel B shows that WNH, Black, and Hispanic women generally had the highest all-ages Alzheimer's disease death rates, especially in the later years of the observation period. Over the entire period, API males had the lowest Alzheimer's disease mortality rates, followed by API females, whose rates were lower than those for males in all other RE groups. Females had substantially higher Alzheimer's disease mortality rates than males in each RE group and the gender gap widened over time. For either sex, WNH individuals had the highest Alzheimer's disease death rate, followed by Black and Hispanic people. From 1999 to 2019, Alzheimer's disease mortality rates rose considerably, especially among the non-WNH RE groups, for whom the rates more than doubled. For instance, all-ages Alzheimer's disease mortality rates rose by a factor of 2.5 among Black females, from 11.8 to 29.0.

In 2019, Parkinson's disease was second only to Alzheimer's disease as the leading cause of death among disorders of the nervous system for WNH, Hispanic, and API males. Unlike the share of nervous system–related deaths caused by Alzheimer's disease, that of Parkinson's disease is higher among males than females in every RE group. For instance, those percentages were 10.2 percent among WNH females, but 23.7 percent for WNH men. Based on a meta-analysis of multiple studies, Wooten and others (2004) estimated that the relative incidence risk of Parkinson's disease is 1.5 times higher for men than women.

Chart 24, Panel C shows that in 2019, WNH males had the highest all-ages Parkinson's disease mortality rate (14.3), followed by Hispanic males (9.1), API males (8.1), and Black males (7.3). The RE groups were similarly ranked among females, with the all-ages death rates ranging from 6.3 (WNH) to 3.0 (Black). From 1999 to 2019, the Parkinson's disease mortality rate increased in every RE/sex group by more than 50 percent and was more than twice as high for men as women, on average.

The subcategory labeled “other degenerative diseases of the nervous system, not elsewhere classified” (which excludes Alzheimer's disease but includes senile degeneration of the brain and degeneration of the nervous system due to alcohol) was the cause of death with the highest mortality-rate increase over the observation period. In 1999, it accounted for 1–3 percent of nervous system disease–related deaths, depending on the RE group (Chart 23). By 2019, however, it exceeded the share of nervous system disease–related deaths caused by Parkinson's disease for females in all RE groups, ranging from 12.1 percent of such deaths among API females to 15.5 percent of them among WNH females.

Chart 24, Panel D shows that the other degenerative nervous system disease mortality rates rose dramatically through the entire 1999–2019 period, driven largely by explosive increases in the 65 or older age group, particularly after 2012.²⁴ API males and females had the lowest increases in all-ages mortality rates in this subcategory over the entire period, yet still they rose by factors of 10.7 and 19.0, respectively. All-ages mortality rates from degenerative nervous system diseases not elsewhere classified rose from 0.5 to 8.9 for WNH males (an 18-fold increase) and rose by a factor of 24 among WNH women. Hispanic males and females experienced mortality rate increases like those of their WNH counterparts, while the rates for Black males and females increased the most, by factors of 22.7 and 35.5, respectively. For each RE group, females had higher all-ages mortality rates than males in 2019. WNH females and males experienced the highest death rates, followed by Black females and males.

Alzheimer's disease, Parkinson's disease, and other degenerative diseases of the nervous system collectively dominate nervous system disorder mortality at ages 65 or older. Because most deaths from nervous system diseases occur at older ages, those three subcategories also account for the overwhelming majority of nervous system disorder–related deaths over all ages combined, constituting more than two-thirds of such deaths in the Black population and more than 80 percent of those for the other RE groups. Nevertheless, other subcategories account for higher shares of nervous system disease–related deaths among people in the midlife and younger ages than among the aged. For example, depending on the RE group, systemic atrophies primarily affecting the central nervous system (such as Huntington's disease and spinal muscular atrophy) accounted for 3–4 percent of nervous system disease–related deaths over all ages combined in 2019. Yet in the midlife ages, systemic nervous system atrophies represented almost 20 percent of nervous disorder deaths among the WNH and API populations, 15.1 percent of those among Hispanic people, and 9.7 percent of those in the Black community.

Chart 24, Panel E shows that at all ages combined, WNH males in 2019 had the highest all-ages systemic atrophies mortality rates across the observation period, followed by WNH females, while API females experienced the lowest mortality rates. For WNH people of both sexes, the all-ages systemic atrophies death rate was 1.8 times that of their Black counterparts. Over the 1999–2019 period, the systemic atrophies death rates remained relatively stable for each RE/sex group.

Episodic and paroxysmal disorders (such as epilepsy and recurrent seizures and migraines) represented a relatively infrequent cause of nervous system disease–related death, accounting in 2019 for 1.5 percent of such deaths in the WNH and API communities, 2.4 percent of those among Hispanic people, and 4.7 percent of such deaths among Black individuals. However, at ages 0–24, it was a leading cause of nervous system disease–related death, accounting for roughly one-quarter of all such deaths in this age group.

Chart 24, Panel F shows that in 2019, Black males and females had the highest all-ages episodic and paroxysmal disorder death rates, followed by WNH males and females; API females and males had the lowest death rates. The all-ages episodic and paroxysmal disorder mortality rate for Black males in 2019 was twice that of WNH males (2.7 versus 1.3). Over the 1999–2019 period, mortality rates rose in all population groups except API women aged 25–64, for whom it remained essentially unchanged.

The all-ages shares of nervous system disease–related deaths attributed to causes in the cerebral palsy and other paralytic syndromes subcategory, which includes paraplegia and quadriplegia, ranged in 2019 from 1.2 percent in the WNH and API communities to 3.0 percent for Black people. This subcategory's share of such deaths has declined over time, is higher among males than females, and is higher at ages 0–64 than at ages 65 or older. It accounts for about one-third of nervous system disease–related deaths at ages 0–24 among Black individuals and close to one-quarter of such deaths for the other RE groups in that age range.

Chart 24, Panel G shows that Black males experienced the highest all-ages cerebral palsy death rate in 2019, followed by WNH males and Black females. All-ages cerebral palsy mortality rates were higher in 2019 than in 1999 for all RE/sex groups other than Hispanic and API males, whose rates were essentially unchanged.

The all-ages share of nervous system disease–related deaths attributed to the “other disorders of the brain and spinal cord” subcategory ranged from 4.2 percent among WNH individuals to 13.5 percent in the Black population. Anoxic brain injury (which occurs when the brain is deprived of oxygen) accounted for more than 60 percent of the deaths in this subcategory. For Black males, this was the second leading all-ages cause of nervous system disease mortality, accounting for more deaths in 2019 than Parkinson's disease and other degenerative diseases of the nervous system. Other disorders of the brain and spinal cord were the leading cause of nervous system disease–related death at ages 25–64 for men of the non-WNH RE groups and for Black and Hispanic women, and were the second leading cause for API and WNH women at these ages.

Chart 24, Panel H shows that Black males had the highest all-ages other brain and spinal cord disorder death rates across the period, followed by Black females and WNH males. From 1999 to 2019, all-ages other brain and spinal cord disorder death rates increased for all RE/sex groups except API males and females. Mortality rates rose by more than 50 percent for Black males (from 4.6 to 7.2) and WNH females (from 1.6 to 2.4).

The residual subcategory labeled “all other nervous system disorders” includes inflammatory diseases of the central nervous system (such as meningitis or encephalitis); diseases of myoneural junctions and muscles; polyneuropathies and other disorders of the peripheral nervous system; nerve, nerve root, and plexus disorders; demyelinating diseases of the central nervous system; secondary parkinsonism; other degenerative diseases of basal ganglia; dystonia; extrapyramidal and movement disorders in diseases classified elsewhere; other extrapyramidal and movement disorders; and various other disorders of the nervous system not classified elsewhere. More than half of the deaths in this subcategory were attributed to disorders of the nervous system not elsewhere classified. In 2019, the disorders in this subcategory accounted for 5–7 percent of nervous system disease–related deaths, depending on the RE group. Regardless of RE group. this subcategory represented a substantially higher proportion of nervous system disease–related deaths in the midlife ages and at younger ages than at ages 65 or older.

Chart 24, Panel I shows that in 2019, WNH males had the highest all-ages all other nervous system disease mortality rate (4.1), followed by WNH females (3.5) and Black females and males (3.1 and 3.0, respectively). In 2019, all-ages other nervous system disease mortality rates among WNH people of either sex were higher than those of their Black counterparts, extending an existing mortality gap between the two RE groups that was driven primarily by mortality experience at ages 65 or older. For instance, from 1999 to 2019, mortality rates among WNH women aged 65 or older rose from 11.0 to 17.6, while for Black women of those ages, they rose only from 9.1 to 11.5.

Chart 25 shows the all-ages nervous system disease mortality rates by cause-of-death subcategory, RE group, and sex in 1999 and 2019. In 1999, death rates were slightly higher for males than for females in the same RE group. By 2019, mortality rates had increased substantially among all RE/sex groups, and by similar magnitudes. For instance, the mortality rates for WNH males and females in 2019 were 60.9 and 61.3, respectively. Similarly, death rates for Black males and females in 2019 were 52.1 and 51.5, respectively. The similarity is surprising, considering the substantial compositional differences: Females experienced higher mortality from Alzheimer's disease and other degenerative diseases of the nervous system, while males had higher death rates from Parkinson's disease and other disorders of the brain and spinal cord.

For WNH males and females, the combined mortality rates from Alzheimer's disease, Parkinson's disease, and other degenerative diseases of the nervous system were significantly higher than those for any other RE group, far offsetting the higher mortality among the Black population associated with other disorders of the brain and spinal cord, episodic and paroxysmal disorders, and cerebral palsy and other paralytic syndromes. A comparison of mortality rates between Black and Hispanic individuals is also interesting, revealing that the disproportionately high mortality rate for other disorders of the brain and spinal cord in the Black population was one of the main factors affecting mortality differentials between the two groups in 2019. At the other end of the spectrum, the death rates from all diseases of the nervous system in the API population were lower than the combined mortality rate from only the two primary causes, Alzheimer's and Parkinson's diseases, in all other RE groups, regardless of sex.