French Fries Linked to Stroke Rates

In a community-based study, individuals living in areas with the highest concentration of fast food restaurants were at 13% higher risk of stroke than those in areas with the lowest density, Lewis B. Morgenstern, M.D., of the University of Michigan in Ann Arbor, and colleagues reported here at the American Stroke Association International Stroke Conference.

"Where we live and where our kids go to school has a profound effect on our health," Dr. Morgenstern said.

Although it's tempting to blame fast-food, Brian Silver, M.D., of Henry Ford Hospital in East Lansing, Mich., who was not involved in the study, agreed that fast-food might be just another marker for community risk factors.

He also said it's important to put the modest risk in perspective. "It's not as important as blood pressure or atrial fibrillation, but if you're trying to look for all potentially modifiable risk factors, this may be one more thing."

The analysis was part of the larger ecological Brain Attack Surveillance in Corpus Christi (BASIC) study, which has looked at a wide range of correlates of stroke in Nueces County, Texas.

Active and passive surveillance identified 1,247 ischemic strokes in county residents from January 2000 through June 2003.
When each case was linked to the census tract of residence, the researchers found a significant association (P=0.02) with the number of nearby fast food restaurants -- defined as having two or more of the following characteristics: expedited service, limited wait staff, takeout business, and payment before being served.

Areas in the top quartile for fast food density with an average of 33 per neighborhood had a 23% higher relative stroke risk (95% confidence interval 1.08 to 1.41) than areas in the lowest quartile with an average of 12.

After controlling for demographic factors including age, gender, race or ethnicity, and socioeconomic status, a higher fast food restaurant density remained significantly linked to stroke risk (RR 1.13, 95% CI 1.02 to 1.25).

Likewise, stroke rates in a neighborhood rose with increasing numbers of local fast-food restaurants. The number of events per 1,000 residents was:

• 0 to 2.0 in the lowest quartile for fast food restaurant density
• 2.0 to 3.4 in communities that fell below the mean but above the 25th percentile
• 3.4 to 4.4 in communities above average but below the 75th percentile
• 5.4 to 8.5 in the highest quartile

Dr. Morgenstern said he was confident that the study captured all stroke cases because of the isolated geography and concentrated healthcare facilities in the area.

However, his team cautioned that the observational study could not prove whether the association was caused by higher consumption of fast food among stroke cases, other unmeasured neighborhood factors such as green space for exercise, or simply a spurious artifact of the study.

But if causal, "the findings have large public health importance due to the high prevalence of fast food restaurants," the researchers said. "These are the neighborhoods that need to be targeted for conventional stroke prevention," Dr. Morgenstern said.

Practice Pearl:
Explain to interested patients that the observational study looked only at neighborhood-level data without the ability to measure individual fast food intake or other risk factors.

American Stroke Association International Stroke Conference
Morgenstern LB, et al "Fast food and stroke risk" ASA 2009; Abstract P162.

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