The modest drop in life expectancy is a result of several top-ten causes of death becoming more deadly than in 2014. Of the top ten causes, eight saw a statistically significant increase, one saw a decrease (cancer deaths), and one stayed the same (deaths from influenza and pneumonia.) The largest climbs were in deaths from heart disease (a.9 percent increase), unintentional injuries (6.7 percent increase), and Alzheimer’s disease (15.7 percent increase). Other top-ten killers, such as strokes, diabetes, and suicide, also increased.
Heart disease remains the number-one killer of Americans, responsible for 23 percent of all deaths. The disease peaked in the 1970s, causing 362 deaths per 100,000 people. In 2014, the amount reached an all-time low of 167 deaths per 100,000 people, measured since the beginning of statistics recording. That number climbed in 2015 for the first time in over 40 years.
The Institute for Health Metrics and Evaluation (IMHE) reports that age, population, and obesity contribute to higher rates of heart disease. All three increased in the United States, especially as the overall population increased some 2.5 million people between 2014-2015.
“Unintentional injuries” is a blanket term for accidental deaths, primarily car accidents, drug overdoses, and deaths by falling. All three increased. The National Safety Council reported that 2015 was the worst year for motor vehicle fatalities since the 1960’s due to an increased amount of drivers (as a result of a stronger economy and low gas prices.) The drug overdose rate has risen dramatically in recent years due to an influx of cheap, powerful opioids from Mexican drug cartels, most prominently heroin. The CDC has declared opioid addiction to be an epidemic. Like heart disease, deaths by falling increase with age as elderly people are far more likely to die from them.
Alzheimer’s disease rates also increase with age. The other causes of the neurodegenerative disorder are disputed, but heart disease, strokes, obesity, and diabetes are all thought to increase one’s risk.
Since heart disease, fall deaths, Alzheimer’s disease, and strokes become more likely later in life, the main cause for falling life expectancy in the US would appear to be its aging population. A secondary cause seems to be an obesity epidemic. Infant mortality, the typical cause for a falling life expectancy, did not change by a statistically significant amount between 2014-2015.
Robert Anderson, a statistician with the National Center for Health Statistics, urged patience before panic. He told NPR that preliminary statistics from the first half of 2016 look promising, and that "we'll have to see what happens in the second half of 2016."
The United States has the world’s 43rd highest life expectancy. Among nations with over 100 million residents, it has the second highest, as Japan, whose life expectancy is a stunning 85 years, is in first place.