The U.S. government’s Centers for Disease Control and Prevention (CDC) recently released a series of reports on life expectancy and causes of death nationwide. In this discussion, health expert Jay Bhattacharya discusses the key findings and explains the trends underlying them.
What surprised you about the studies?
The academic discourse around life expectancy in the past few years has really just been focused on looking for signs of a possible slowdown in the rate at which it has been increasing. What the CDC has now revealed is a real reduction in the anticipated life spans of human beings born today. Up until recently, we as demographers had been debating what the limits to human longevity might be, but now we’re now being forced to answer a totally different question about why that positive trend, which we’d assumed was going to continue for a while, has been so suddenly thrown into reverse.
What possible reasons have been floated to explain this decline? Do you find them credible?
A lot of the discussion in the media after the CDC released these reports was focused on increased deaths from opioid abuse and suicide. The theory goes that because of the increasing prevalence of suicide, depression, drug abuse, and so forth — which tend to begin in younger populations — that there’s more of an impact on life expectancy relative to, for example, a disease hitting people who are 80- or 90-years-old. Deaths among the younger group have a bigger impact on life expectancy than deaths among the elderly, because of the difference in the number of years of life lost.
But my personal view is that these factors, although they might have a particular political salience right now, aren’t actually the main reasons for the decline that the CDC is reporting.
What alternative would you offer?
A lot of the previous demographic literature has focused on changes in chronic disease rates in the American population and in particular on obesity. There’s been this enormous and persistent rise in the prevalence of obesity going back decades, which even continued through the aftermath of the 2008 financial crisis, when some people thought the rise in food prices would flatten it out.
In the U.S. today, around 40% of the adult population is obese and correlates very strongly, causally even, with diabetes and all kinds of other chronic conditions that are not just expensive to treat but also lead to increased mortality. That mortality does tend to manifest a little bit later in life than for suicide and opioid-related causes of death, and so the effect of each individual death has a smaller impact on life expectancy. But when we’re talking about nearly half of the American population being at risk for obesity-related mortality, that has an enormous effect on aggregate.
Why has this trend of increasing obesity been so persistent?
It’s a combination of technological changes in agricultural production and in our lifestyles. The former has reduced the price of food (i.e. calories), so following the economic logic of supply and demand, people are going to purchase and consume more calories. Granted, this is checked to some degree by homeostatic mechanisms — basically, your body has ways of telling you that you’ve eaten enough — but these are imperfect in major ways. Then the other side of the equation is how many calories we’re burning, and in particular how active we are in our day-to-day lives. The growth in obesity rates has coincided with technological advances that have made our professional lives less physically active, and we’re spending more and more time sedentary — in front of screens — both while we’re on the clock and when we’re at home.
Both halves of this equation are putting upward pressure on obesity rates. Less calories are being burned and more calories are being consumed, so we shouldn’t really be surprised that obesity rates are increasing in almost every single country on Earth.
How should we go about reversing these trends?
One thing that I think we need to be better at is distinguishing between primary prevention and secondary care. The latter we’ve gotten very good at, the former not so much. For instance, while chronic disease rates have risen dramatically in the U.S., disability from that chronic disease hasn’t to the same extent. We’re better at treating people who’ve had a heart attack or a stroke so that they don’t end up seriously disabled, but in terms of preventing those primary health events from happening, by targeting risk factors like obesity, we’re not doing enough.
So how should we be spending health-care dollars to maximize their positive impact on outcomes like life expectancy?
This is a tricky question, because it gets into the highly-political distributional questions around health care, as well as the way that these questions tie into other types of social inequality. When it comes to socioeconomic status, the lowest quintile has experienced almost no change in life expectancy over the last 20 years whereas as the highest quintiles experienced very substantial life-expectancy increases. In developed countries, it also tends to be the relatively poor who are most likely to be obese; about 1.5 times more likely in the U.S.
Exactly how we should go about addressing this imbalance isn’t clear, since it’s necessary to also consider all the social inputs that go into health outcomes; not only, for instance, communities’ access to health-care services. Certainly though, we should be asking where the marginal value of health-care dollars is highest and target those areas. For instance, the costs of preventative or primary medicine relative to rehabilitative or secondary care are much lower, so working on novel and effective ways to encourage people to take better care of themselves before they experience some kind of major illness will be critical. In my view, we also need to do a lot more research to truly understand the causes of this decline in life expectancy if we’re going to be able to turn things back around.
Views expressed here do not necessarily represent those of the Freeman Spogli Institute for International Studies or Stanford University, both of which are nonpartisan institutions.