To What Extent is Health Care Responsible for Our Longer Lives?

I pointed out in one of my “It’s been a great century” posts that not all of the reduction in cardiovascular disease specific mortality is due to medical interventions. My other “It’s been a great century” post focused on great strides in public health, which deserves much of the credit for our longer lives.

It’s famously hard to deduce exactly how much credit to give public health and how much medical care, even for a specific disease. In a year 2000 NEJM paper by Hu et al. the authors estimate that between the early 1980s and the early 1990s,

the reduction in smoking explained a 13 percent decline in the incidence of coronary disease; improvement in diet explained a 16 percent decline; and increase in postmenopausal hormone use explained a 9 percent decline. On the other hand, the increase in body-mass index explained an 8 percent increase in the incidence of coronary disease.

However, they also write, correctly, that a limitation of their results is that they

do not imply that other factors, such as levels of blood pressure and serum cholesterol, are unimportant or do not contribute to this decline, because the effects of diet and lifestyle are partially mediated by their effects on blood pressure and serum cholesterol. […] In the Framingham Study, the increasing use of antihypertensive medication from 1950 to 1989 was associated with a downward trend in the prevalence of hypertension and a concomitant decline in left ventricular hypertrophy.

David Cutler, Allison Rosen, and Sandeep Vijan (NEJM, 2006) split the difference right down the middle: 50% of declines in mortality due to medical care, 50% due to other factors. They cite studies to back this up. I have not read them yet.

Analyses aggregated from treatments clearly shown to be medically effective suggest that at least half the life-expectancy gains since 1950 are due to medical advances.[11-13] About 90 percent of the gains in life expectancy are attributable to improvements in the rates of death in infancy and the rates of death from cardiovascular disease. Prevailing estimates suggest that at least half the reduction in these rates are due to medical care.[4,14-23] We therefore assumed in our base case that 50 percent of the total gains in life expectancy were due to medical care. […]

This assumption is likely to be reasonable, given our finding that 90 percent of the increases in life expectancy during the past four decades have resulted from reductions in the rate of death from cardiovascular disease and death in infancy. Although reductions in the rate of death from cardiovascular causes are multifactorial, prior research has suggested that at least half the reductions in the rate have resulted from medical advances.[14-17] Among infants, more than half the reduction in the mortality rate between 1960 and 2000 resulted from a reduced rate of neonatal death among lowbirth- weight infants (weighing <2500 g), which is due almost entirely to medical advances.

About cardiovascular disease in particular, Cutler, Deaton, and Lleras-Muney write in a 2006 Journal of Economics Perspectives article,*

Since 1960, cardiovascular disease mortality has declined by over 50 percent, and cardiovascular disease mortality reductions account for 70 percent of the seven-year increase in life expectancy between 1960 and 2000. Cutler (2004) matches the results of clinical trials to actual mortality declines, and attributes the bulk of the decline in cardiovascular disease mortality—as much as two-thirds of the reduction— to medical advance. Beyond medical advance, the major factor in reduced cardiovascular disease mortality is the reduction in smoking. Smoking rates in the United States have fallen to half their level at the time of the Surgeon General’s 1964 report on the harms of smoking. Continued public health campaigns against tobacco use have been an important part of this decline.

If all this supporting evidence is sound and convincing, medical care is holding its own. It’s even worth the price, say Cutler and colleagues.

According to virtually any commonly cited value of a year of life, we found that if medical care accounts for about half the gains in life expectancy, then the increased spending has, on average, been worth it.

Loaded with waste, yes, but still worth buying at prevailing prices. Of course if price (or cost) outpaces longevity gains, that won’t be true forever. This ignores gains in quality of life, which further enhances the value per dollar spent.

* Highly recommended and ungated.

[Cross-posted at The Incidental Economist]

Austin Frakt

Austin Frakt is a health economist and an assistant professor at Boston University's School of Medicine and School of Public Health. He blogs at The Incidental Economist.