Notes Washed Up in a Bottle

Don. W. MacCorquodale M.D. M.S.P.H.

Periodic Notes From the Field on Philosophy and Science.

LIFE EXPECTANCY

          In a special report in the NEJM, S. Jay Olshanksy and his colleagues suggested the life expectancy may decline in the United States in the near future (Olshansksy S J et al.   A potential decline in life expectancy in the United States in the 21 st century.   NEJM 2005; 352:   1138-1145).   The authors pointed out that the proportion of Americans who are obese is increasing rapidly.   They calculated life expectancy using two models for estimating the conditional probability of death:   one incorporated the proportion of Americans who are obese, and the other incorporating the probability of death for the obese.   The researchers calculated that life expectancy may decline by one third to three fourths of a year.  

          The authors pointed out that the age-adjusted death rates from infectious disease rose 39 percent between 1980 and 1992, an increase largely due to the AIDS epidemic.   There has also been an increase in hospital-acquired infections, and antibiotic-resistant infections are increasingly problematic.   A pandemic of a particularly virulent variety of influenza would almost certainly have an influence on life expectancy.

          In an editorial in the same issue of the NEJM, the distinguished demographer, Samuel H. Preston expressed his doubts that the United States will face a decline in life expectancy (Preston S H.   Deadweight? – The influence of obesity on longevity.   NEJM 2005; 352:   1135-1137).   Dr. Olshansky and his co-authors suggested that much of the increase in life expectancy in our country has been due to declines in infant mortality and mortality in young children.   Professor Preston pointed out, however, that 60 percent of the more than 9 percent increase in life expectancy at birth between 1950 and 2002 has been due to decreases in mortality among people older than 50 years.  

          He added that medical research has been responsible for the “massive decrease” in deaths from cardiovascular disease, and he suggested that the National Institutes of Health and private companies will continue to develop new products that will “enhance health and longevity.”

          Professor Preston wrote that “mortality is profoundly influenced by education,” and he indicated that younger cohorts are much better educated than older cohorts.   In 1998 life expectancy at age 24 years was slightly more that 7 years greater for men with some college education than it was for men who had only a high school education.  

          Far fewer younger people are smoking cigarettes today than they were a few decades ago, and this is certain to reduce the incidence of certain cancers, cardiovascular disease, and emphysema.  

          The change in American life styles is most encouraging.   “Forty-two percent of Americans were smokers in 1965, as compared with percent in 2000.   The percentage of Americans 20 to 74 years of age with high levels of serum cholesterol fell from 33 percent in 1961 to 18 percent in 1999 and 2000.   Primarily because of behavioral changes the incidence of AIDS has fallen by nearly 50 percent since 1992.”  

          Lastly, Professor Preston suggested that “small behavioral changes” could arrest the trend toward increasing prevalence of obesity.

          COMMENT:   Despite the fact that I generally see the bottle as half empty, rather than half full, I find Professor Preston's argument very persuasive.   I was however a bit surprised that he stated that “mortality is profoundly influenced by education.”   I have long felt that the lower mortality rates among educated adults are a reflection of the influence of social class, which is a more complex characteristic than educational attainment alone.    

DEMOGRAPHIC CHANGE IN EUROPE

          The European Commission of the European Union has issued a consultation paper announcing that the later is facing unprecedented population change (Watson R.   News.   Falling EU population will affect healthcare provision.   BMJ 2005; 330:   692).   The native population of the EU's 25 member countries increased by just 0.04% in 2003, and of the ten countries that joined the EU last year, all saw their populations decrease in size, except Cyprus and Malta .   Throughout the EU the fertility is below the replacement level, 2.1 children per woman, and in 16 countries it has fallen below 1.5.  

          The EU's present population will increase by just 2% by 2025 and only because of immigration.   Thereafter, it will start to decline.   On the other hand the number of people living in the United States will continue to increase by 26% over the next two decades.  

          Between this year and 2030 the number of people of working age, 15-64 years, in the EU will fall by almost 21 million.   The paper estimates that by 2030, every two economically active persons in the EU will have to support one inactive person.   Of the five largest countries in the EU, population increases over the next 45 years will be seen solely in the United Kingdom (8%) and in France (9.6%).

          COMMENT:   This report does not address the reason for the continued growth of the American population, but it is clear that it is largely the result of continued immigration.  

          I was surprised to see the projections of the growth of the population of the UK and of France , for the rates of annual growth in those countries are very low.   In France , the rate of annual increase in the population was 0.5% in 2000, and it was projected to be 0.1% for the year 2005 (US Bureau of the Census).   The corresponding rates for the UK were 0.4% for 2000 and 0.2% for 2005.

MOBILE PHONES AND THE RISKOF BRAIN TUMOR

          The results of most previous studies of brain tumors in relation to the use of mobile phones have been negative, although a Finnish study and a Swedish study showed an increased risk (Lonn S et al.   Long term mobile phone use and brain tumor risk.   Am J Epidemiology 2005; 161:   526-535).  

Studies of ionizing radiation have suggested that the induction period for solid tumors due to exposure to ionizing radiation is probably 10 years at the least.   Sweden is an ideal country in which to study the question because handheld mobile phones were introduced there in the late 1980s and were widely accepted very quickly.

          The authors conducted a case-control study of a population of 3.7 million people living in areas covered by three regional cancer registries.   Eligible cases were all individuals diagnosed with either glioma or meningioma during the study period of September 1, 2000 and August 31, 2002.   A total of 499 glioma cases and 320 meningioma cases were diagnosed.   Controls were randomly selected from the study population stratified on 5-year age groups, gender, and residential area.  

          Regular mobile phone use was defined as use of a mobile phone at least once a week on the average during the last six months.   Time since first regular use was categorized as less than 5 years, 5-9 years, and 10 or more years.   Unconditional logistic regression was employed to calculate odds ratios and 95% confidence intervals.  

          For regular mobile phone use, regardless of duration, the odds ratio for glioma was 0.8; 95% CI:   0.6,1.0, and it for meningioma it was0.7; 95% CI:   0.5,0.9).   The odds ratio for 10 years or more of mobile phone use, 25 cases and 38 controls, was 0.9; 95% CI:   0.5, 1.5, for glioma, and for the same duration of use, 12 cases and 35 controls, it was 0.9; 95% CI:   0.4, 1.9, for meningioma.  

          The authors concluded that their findings did not support the hypothesis that mobile phone use is related to increased risk of glioma or meningioma.

          COMMENT:   Note the small numbers of cases involved in the estimation of risk for 10 years duration of mobile phone use.   Clearly, we are going to have to await additional studies to be able to establish with some degree of confidence that mobile phone use is or is not associated with increased risk of brain tumors.