Nationwide study gives tobacco ban advocates a smoking gun

A nationwide analysis may snuff out lingering doubts about the health benefits of smoking bans in public indoor places. A study that examined the association between smoking bans enacted in the U.S. between 1991 and 2008 and hospital admissions for smoking-related illnesses found a significant drop in admissions for acute MI and chronic obstructive pulmonary disease (COPD).

The study was published in the December issue of Health Affairs.

Many previous studies have reported an association between smoking bans and lower hospital admissions for acute MI, wrote Mark W. Vander Weg, PhD, of the University of Iowa Carver College of Medicine in Iowa City, and colleagues. But generally the studies focused on single cities or counties in the U.S., while national studies in Scotland and New Zealand failed to provide controls. 

“Thus, despite many useful findings and some methodological advances, the smoking literature still largely lacks research based on broad national data, comprehensive information on a wide variety of smoking laws, assessment of effects for a range of conditions and adequate controls for confounding factors,” they wrote.

Vander Weg and colleagues designed their study to encompass clean air laws enacted in more than 3,100 counties across the U.S. with an extended period to capture hospitalizations for acute MI and COPD. For a control, they also examined hospital admissions for gastrointestinal hemorrhage and hip fracture. The study focused on Medicare beneficiaries who were 65 years old or older and smoking bans in three settings: restaurants, bars and work places.

They calculated risk-adjusted hospital admission rates using the U.S. Tobacco Control Laws database to identify 938 smoking bans in 3,132 counties that were enacted between 1991 and 2008; Census Bureau data to calculate the proportion of the population covered by the bans; Centers for Medicare & Medicaid Services files to determine Medicare population characteristics; Medicare provider data to count the number of acute hospitals in each county; and Medicare Denominator and hospital discharge data to measure hospital admissions by condition.

Overall, risk-adjusted admission rates for AMI fell 20 percent in counties that implemented new smoking bans, 36 months or later after the laws were put in action. The rate for COPD was 17 percent after 36 months. Smoking bans had minimal effect on gastrointestinal hemorrhage and hip fracture admission rates.

Having bans in two or more settings improved acute MI admission rates even more. Counties saw rates drop an additional 14 percent compared with counties with no bans if implemented in two settings and 16 percent if implemented in three settings. Rates did not decrease significantly if a ban was introduced in only one setting, though. The results for COPD were similar.

“Consistent with prior investigations, we found that smoke-free legislation was associated with a significant reduction in hospitalizations for acute MI and that the rate of decline increased over time,” Vander Weg and colleagues wrote. “In addition, a ‘dose response’ effect was found, meaning that the health impact of the bans tended to increase when they were applied to multiple venues.”

They pointed out that their finding of a 20 percent reduction at 36 months was more modest than other studies. They attributed the difference to the larger and more diverse population in their study and age-related differences in the impact of smoking bans and hospital admissions.

Their study didn’t evaluate secondhand smoke exposure, distinguish between smokers and nonsmokers, account for people with existing cardiovascular disease or ascertain that bans were enforced. The authors added their estimate of reductions in admissions for acute MI and COPD may be conservative, based on census data showing that counties initiating new bans during the study period tended to be more affluent. Since poverty level is associated with tobacco use, they suggested smoking bans would have more impact in counties with a greater proportion of smokers.