The “Stroke Belt” May Also Be a “Cognitive Decline Belt”

In January this year I blogged about how 8 states in the southeast of the USA – North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas, and Louisiana - have an increased incidence of stroke in their populations. The tentative explanation is a difference in the type of fish being eaten; people in this belt eat more fried fish, and less non-fried fish.  Now researchers have used the same database to determine if there’s a possible association between a person’s state of residence and their risk of impaired cognition.  Their findings are reported online in the Annals of Neurology.

The 24,000-odd participants in the study were 45 or older, and had no cognitive impairment or history of stroke at baseline.  Their cognitive status was assessed annually using the Six-Item Screener (SIS) test, which is based on the widely-used Mini-Mental State Exam (MMSE).  Every 2 years they underwent fluency and recall tests.

Of the total sample, 8.1% of participants over a 4-year period declined to an SIS score in the impaired cognition range.  After adjustments for age, gender, race, and education level, Stroke-Belt residents were 1.18 times as likely to develop cognitive impairment as non-Belt residents.  If the analysis was confined to the two most recent assessments – with 438 participants – the odds of cognitive impairment were even higher (1.4 times).

These results are not too surprising, given that stroke and cognitive impairment have several known shared risk factors: high blood pressure, diabetes, kidney disease, etc.  Although an overt stroke would have excluded the subject from the analyses, it’s possible that minor changes in the white matter of the brain, such a silent stroke, could be the responsible pathology in the cognitively impaired.  Although not mentioned, too much fried fish may even have been a decisive factor, as in the stroke study . . .