Watch: What is life expectancy and why is it declining?

The average life expectancy in the US has been on the decline for three consecutive years. A baby born in 2017 is expected to live to be 78.6 years old....that’s down from 78.7 the year before. That means in just a year, the average American’s life expectancy has been shortened by 1.2 months.

The last three years represent the longest consecutive decline in the American lifespan at birth since the period between 1915 and 1918, a period that included World War I and the Spanish Flu pandemic, events which killed tens of millions worldwide.

Before the recent decline, life expectancy was steadily rising in the US — which is to be expected of an advanced nation, particularly one that spends more money per citizen on healthcare than any other country.

But this trend isn’t unique to the States.

One recent study projected the UK lifespan will shorten by about five months. And while life expectancy is still on the rise in France, Germany, Sweden and the Netherlands, these countries have also seen a sharp slowdown.

Historically, life expectancy in the U.S. was on par with other OECD countries — a basket of other developed nations.

But in the last years, that’s changed, with the OECD average pulling ahead of the U.S. in life expectancy.

It’s also important to note, that even within the US, life expectancy can vary greatly by state.

Here in California, the life expectancy is 80.9.

That makes it the second highest state in the country after Hawaii, which has a life expectancy of 81.3.

The state with the lowest life expectancy is a striking six years behind. That’s Mississippi with at 74.7 years. Many of its neighboring states in the south follow closely behind.

Life expectancy also differs by sex. Men can expect to live 76.1 years at birth, while women in the U.S. are expected to live 81.1 years.

So why is life expectancy coming down in the US?

Well, while there’s no single cause, a report by the Centers for Disease Control and Prevention, or CDC, highlights three things contributing to the decline.

In 2017, more than 70,000 deaths occurred because of drug overdose. Of these, opioids were involved with over 47,000 (47,600).

The age-adjusted death rate for drug overdose in the U.S. shot up a whopping 72 percent within a decade.

When the Center for Disease Control, or CDC, analyzed data from emergency room visits, it found that opioid overdoses went up a whopping 30% in the U.S. from July 2016 and September 2017.

Opioids continue to be prescribed at triple the amount that was given in 1999.

But there could be hope. The federal government has spent more than $2.4 billion in state grants since 2017, hoping to curb the epidemic.

And data from the CDC shows the number of opioid prescriptions, while still high, is now declining.

Over a ten year period, the death rate for chronic liver disease and cirrhosis among men aged 25 to 34 increased by nearly 8 percent per year. For women in the same age group, the increase averaged more than 11 percent per year.

The causes of liver disease can vary, from genetics to alcohol consumption and obesity.

And America’s love for fast food certainly doesn’t help. A survey found more than 1 in 3 Americans eat fast food every single day.

The national suicide rate has increased by 33 percent since 1999, and in 2017 alone, they went up by 3.7 percent.

This jump is out of sync with the rest of the world. The global suicide rate has declined by almost 30 percent since 2000, with the rates in Russia, Japan, South Korea and India falling significantly over the last decade.

Location is significant within the US as well.

The country’s most rural areas have suicide rates almost twice as much as those in urban communities.

A number of statistical studies have shown that in general, individuals born in wealthier countries can expect to live longer than those born in poorer countries.

A reduction in poverty implies better access to food, housing, education and health services - things that should help extend your life.

However, the relationship between income and life expectancy weakens once it hits a certain level. The US - the world’s biggest economy - is one of the most notable exceptions to the income-life association.

After several years of slight declines, it’s hard to know whether the U.S. life expectancy will fall any further or flatten, but there’s one thing that’s for sure...public health experts are alarmed.