US people’s shorter lifespans, when compared to rival countries is in great part because people in America used to smoke a lot, as well as having considerably higher than global average rates of obesity, says a new report issued by the National Research Council. Although life expectancy at age 50 has been rising in the USA over the last two or three decades, other countries have been pulling ahead at a faster rate.

These figures are surprising, given that the USA spends a considerably higher percentage of GDP than its rivals. The National Institute on Aging says it plans to find out why this is so.

During the 60s and 70s smoking prevalence was considerably higher in the USA than in Japan or Western Europe. The effects of a past history of smoking often linger for several decades, the authors explain. The difference in life expectancy today between European/Japanese and American women is mainly due to higher smoking rates in the USA in the past. The report explains that in the Netherlands and Denmark, smoking is the main cause of lower life expectancies when compared to other high income nations.

The lingering effects of regular smoking persevere to varying extents for twenty to thirty years after an individual has quit. Over the coming 20 to 30 years male life expectancy is expected to greatly improve in the USA, because a higher proportion of men gave up over the last 20 years compared to women.

US female smoking rates peaked later than their male counterparts, the authors explain. Therefore, female declines in mortality will probably take longer to become noticeable.

Japan will see even slower improvements, because its peak occurred relatively recently.

The obesity epidemic is also a big factor. More people are obese in America than any other developed country. The authors believe that from a fifth to one third of reduced longevity is linked to obesity. In fact, obesity rates continue to rise and there is a serious risk that they might wipe out any expected improvements in lifespans. Some data coming in this year indicate, however, that rates of obesity may be peaking, may hopefully mean an eventually lower mortality risk.

Unlike many of its rivals, in the USA a comparatively large number of people do not have health care cover, and some of those who do have insufficient cover. This is thought to negatively affect life expectancy. As the over 65s in America have access to Medicare, lack of universal access to healthcare is a less significant factor than obesity and past smoking.

The two main causes of death among the elderly in America – cardiovascular disease and cancer – are not better treated or more effectively prevented in other comparable nations, the authors explained. In fact, the USA fares better than most other nations in heart attack survival rates and cancer detection and survival.

In a communiqué, the National Research Council wrote:

“Certain risk factors are unlikely to have played a major role in the divergence of life expectancy over the last 25 years, the report adds. Although a large body of emerging work suggests that there may be important connections between the strength of social ties and mortality, the committee that wrote the report found little compelling data to indicate that differences in social networks among people in high-income countries are related to the differing patterns of life expectancy.

Similarly, little evidence supports the hypothesis that hormone therapy has played a part in the relatively lower longevity for American women.

There are several gaps in research, the study committee found. Lung cancer deaths are a reliable marker of damage caused by smoking – as far as obesity, physical activity, social integration or other risks mentioned in the report are concerned, no clear-cut marker exists.

The National Research Council added:

While there is no perfect substitute for randomized controlled trials, studies that take advantage of natural experiments, such as increased cigarette taxes or a dramatic change in the use of hormone therapy, can sometimes serve as valuable supplements to them.

“Explaining Divergent Levels of Longevity in High-Income Countries”
Eileen M. Crimmins, Samuel H. Preston, and Barney Cohen, Editors; Panel on Understanding Divergent Trends in Longevity in High-Income Countries; National Research Council
(This report is for sale)

Written by Christian Nordqvist