• Want to live longer? Breath clean air
     | December 12,2012

    Continuing declines in air pollution are linked to increasing life expectancy, a national study has found.

    From 2000 to 2007, air pollution, as measured in concentrations of particulate matter less than 2.5 micrometers in diameter, has continued to decrease, although not as rapidly as in the 1980s and ‘90s. But even the slower rate of decrease is apparently lengthening life expectancy.

    The study, published online last week in the journal Epidemiology, used data from 545 counties nationwide, both metropolitan and rural, and found an average decrease of 1.56 micrograms per cubic meter in particulate pollution over the eight years. At the same time, life expectancy increased an average of 0.84 years.

    Of course, many other factors contribute to increased life span besides cleaner air. The researchers controlled for smoking prevalence, income and other health and economic factors. They estimated that about 18 percent of the increase in life span can be attributed to reduced air pollution.

    “What this means is that even if particulate pollution has been declining in recent years at a slower rate, even if we have already done a lot of cleanup, still continuing to clean is important,” said the senior author, Francesca Dominici, a professor of biostatistics at the Harvard School of Public Health. “Our paper is strong evidence that additional investment in cleaning the air is beneficial.”

    Efficacy of tobacco taxes tied to gene type

    Tobacco use has declined sharply since the 1960s, but for the past 20 years about 20 percent of the population has continued to smoke. The imposition of steep tobacco taxes in many states has not lowered the smoking rate.

    Now an economist has published an unusual study in the December issue of PLoS One that suggests a reason: About half the population has a variation in a specific gene connected to nicotine addiction that makes them more likely to respond to cigarette tax increases.

    Jason M. Fletcher, an associate professor of health policy at Yale, used data on 6,178 adults in a large national health survey that gathered information on smoking habits and also collected biological specimens for genotyping.

    About half of the subjects had a variation in a gene for a nicotine receptor in the brain that is thought to control the pleasure reward of nicotine consumption. Fletcher tracked the statistical relationship between taxation, smoking and this gene.

    He found that a 100 percent increase in taxes had a significant effect only on people with this particular genetic variation in DNA sequence. The other half of the population was immune to the effect of taxation.

    Fletcher urged caution in interpreting his findings since this is the first study of its kind. Still, he said, “As we get more and more convinced that people with certain genotypes may respond differently to policies, that means that alternative policies may be necessary.”

    Smoking tied to less dense bones for girls

    Smoking in teenage girls is associated with slower development of bone mineral density, a new study reports.

    The scientists studied 262 healthy girls ages 11 to 19, using questionnaires and interviews to assess their smoking habits. The researchers also measured the girls’ bone density at the hip and lumbar spine three times at one-year intervals.

    Smokers entered adolescence with the same lumbar and hip bone density as nonsmokers, but by age 19, they were about a year behind on average. After adjusting for other factors that affect bone health — height, weight, hormonal contraceptive use and more — the researchers found that even relatively low or irregular rates of smoking were independently associated with lower bone density.

    The study, published last week in The Journal of Adolescent Health, used a sample that fell below national averages for calcium intake and physical activity, so the results may not be generalizable to wider populations.

    The lead author, Lorah D. Dorn, a professor of pediatrics at Cincinnati Children’s Hospital, pointed out that this is only one study and that more research is needed. Still, she said, “It tells me that for care providers — clinicians and parents — this needs to be something they’re vigilant about.”

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