Hospital Admissions for Myocardial Infarction and Stroke Before and After the Trans-Fatty Acid Restrictions in New York

Abstract

Importance: Trans-fatty acids (TFAs) have deleterious cardiovascular effects. Restrictions on their use were initiated in 11 New York State (NYS) counties between 2007 and 2011. The US Food and Drug Administration plans a nationwide restriction in 2018. Public health implications of TFA restrictions are not well understood.

Objective: To determine whether TFA restrictions in NYS counties were associated with fewer hospital admissions for myocardial infarction (MI) and stroke compared with NYS counties without restrictions.

Design, setting, and participants: We conducted a retrospective observational pre-post study of residents in counties with TFA restrictions vs counties without restrictions from 2002 to 2013 using NYS Department of Health's Statewide Planning and Research Cooperative System and census population estimates. In this natural experiment, we included those residents who were hospitalized for MI or stroke. The data analysis was conducted from December 2014 through July 2016.

Exposure: Residing in a county where TFAs were restricted.

Main outcomes and measures: The primary outcome was a composite of MI and stroke events based on primary discharge diagnostic codes from hospital admissions in NYS. Admission rates were calculated by year, age, sex, and county of residence. A difference-in-differences regression design was used to compare admission rates in populations with and without TFA restrictions. Restrictions were only implemented in highly urban counties, based on US Department of Agriculture Economic Research Service Urban Influence Codes. Nonrestriction counties of similar urbanicity were chosen to make a comparison population. Temporal trends and county characteristics were accounted for using fixed effects by county and year, as well as linear time trends by county. We adjusted for age, sex, and commuting between restriction and nonrestriction counties.

Results: In 2006, the year before the first restrictions were implemented, there were 8.4 million adults (53.6% female) in highly urban counties with TFA restrictions and 3.3 million adults (52.3% female) in highly urban counties without restrictions. Twenty-five counties were included in the nonrestriction population and 11 in the restriction population. Three or more years after restriction implementation, the population with TFA restrictions experienced significant additional decline beyond temporal trends in MI and stroke events combined (-6.2%; 95% CI, -9.2% to -3.2%; P < .001) and MI (-7.8%; 95% CI, -12.7% to -2.8%; P = .002) and a nonsignificant decline in stroke (-3.6%; 95% CI, -7.6% to 0.4%; P = .08) compared with the nonrestriction populations.

Conclusions and relevance: The NYS populations with TFA restrictions experienced fewer cardiovascular events, beyond temporal trends, compared with those without restrictions.

Figure 1.. Highly Urban New York State Counties With and Without Trans-Fatty Acid Restrictions

Modified New York State county map courtesy of the US Geological Survey (modified by the author).Urban Influence Codes were obtained from the US Department of Agriculture Economic Research Service 2003 data collections for Urban Influence Code. Urban Influence Code 1 represents large metropolitan areas with at least 1 million residents. Urban Influence Code 2 represents small metropolitan areas with fewer than 1 million residents. Counties with restrictions include Bronx, Kings, New York, Queens, and Richmond starting on July 1, 2007; Westchester on January 15, 2008; Nassau on April 1, 2008; Albany on January 1, 2009; Suffolk on October 28, 2010; Rockland on January 1, 2011; and Broome on December 1, 2011.

Figure 2.. Temporal Trends in Myocardial Infarction and Stroke Event Rates in Urban Influence Codes 1 or 2 New York State Populations With and Without Subsequent Trans-Fatty Acid (TFA) Restrictions

Each point corresponds to an annual admission rate. Years 2007 and 2008 have points corresponding to each half year during the period of multiple restriction implementations. Data are age-adjusted to the national population in 2010.