Friday, January 27, 2012

Worried Sick: The Age of Anxiety

   It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, ...

Charles Dickens,  A Tale of Two Cities 

     Dickens' words, written in 1859,  could aptly describe contemporary society's experience of health and modern medicine, miraculous or mistaken, death defying or dubious.  This is a curious state of affairs when one considers the remarkable success medicine has had since the Second World War. A timeline of some medicine's greatest hits reflects this golden age:

Penicillin 1941 
Cortisone 1949
Smoking identified as cause of lung cancer and Tuberculosis cured with streptomycin and PAS 1950 Chlorpromazine for schizophrenia and the first intensive care unit 1952 
Open heart surgery and polio vaccine 1955  
Cardiopulmonary resuscitation 1956 
Endoscopy 1959 
Oral contraception 1960 
Levodopa for Parkinson's disease and hip replacement surgery 1961 
Kidney transplantation 1963 
Stroke prevention programs and coronary bypass grafting 1964 
Heart transplantation 1967 
Prenatal diagnosis of Down's syndrome 1969
Neonatal intensive care 1970
Cure of many childhood cancer 1971
CAT scanner 1973
First test-tube baby 1978
Coronary angioplasty 1979
Helicobacter identified as cause of peptic ulcer 1984
Thrombolysis for heart attacks 1987
Triple therapy for AIDS rendering it a nonfatal illness 1996
Viagara therapy for impotence 1998

     The previous 2,000 years had seen no significant therapeutic discovery for the scourges of infant mortality, infectious disease, surgical death, cancer, heart disease or mental illness. In 1900, 30% of all deaths occurred among children aged less than 5 years.  By the end of the century, that percentage was only 1.4%. In 1900, the three leading causes of death were pneumonia, tuberculosis, and diarrhea, which (together with diphtheria) caused one third of all deaths. Of these deaths, 40% were among children aged less than 5 years. At century's end these diseases were scarce. Heart disease and cancers accounted for more than half of all deaths, with only 4.5% attributable to infectious disease.

     The 20th century witnessed a 30 year increase in life expectancy.

     And yet, despite these unprecedented advances, more people feel uneasy about their health today than in 1900 or 1940.


     I believe that two events on the hit parade of 20th century medical accomplishment can explain much of the paradoxical loss of confidence in our health; the discovery that smoking caused lung cancer and the realization that high blood pressure caused stroke.

     Let's take them one at a time.

     The revelation that smoking, a nearly universal postwar habit, caused a fatal illness introduced the idea that health was tied to lifestyle. A habit that seemed to cause no harm in the short term could kill you. From that time forward, people had to wonder what other behaviors might prove lethal. 

     The impact of connecting high blood pressure to stroke was more insidious. Hypertension is usually silent, causing no symptoms. You go about your business feeling fine. Prior to the discovery that high blood pressure causes stroke, it was fair to presume that if you felt well, you were well. Suddenly how you felt was no guarantee. You no longer had to be sick to visit a doctor. In fact, annual visits became the norm. 

     The remarkable medical breakthroughs of the latter half of the 20th century also fostered a view that medicine's domain had no limits. All human problems could be remedied by the mighty medical establishment. This expansionism brought annual crops of new diagnoses and new vulnerabilities.
The long arm of medicine now reaches into our living rooms where big pharma describes symptoms and cures on the television, lest we thought we were well. 

     The most conspicuous example of such thinking today is the conceptualization of obesity as a medical illness. Bullets cause bleeding but cannot be understood as a medical issue. Obesity's roots lie in bad foods and inactivity, not failures of medicine. The solution will  not be gastric stapling or a pill.

     No doubt, part of this bizarre way of thinking can be owed to the origins of medicine. It has been a field of fixing what's broken. Only recently and reluctantly has it begun to embrace prevention. But there is no question that now our habits are the leading cause of illness. More americans are unhealthy today than in 1900 despite medicine. And we are a more anxious lot, fearful that our cell phones, water bottles, foods, air, are all potential killers. But none of this is in the medical realm.

     Perhaps we must look to those most gifted at changing people's behavior. That has never been the doctors. Madison Avenue and the admen, pop idols, sports icons. We must enlist them as health evangelists if we are ever to see anything like the progress of last century. 





Friday, January 13, 2012

One Billion Beats?

     For some time researchers have noted a strong link between heart rate and survival,  an association that holds true for most mammals. Most small mammals have a rapid heart rate and a  short life expectancy, while large mammals have a significantly slower heart rate and a correspondingly longer life span. For the majority of mammals, large and small, life expectancy is approximately 1 billion heartbeats.

     Investigators have played with this information and successfully prolonged the life span of mice by slowing their heart rate. So where do we humans fit in?

     We are no exception. A large epidemiological literature documents the association between heart rate and mortality. Resting rates as low as 75 to 80 beats per minute are associated with significant increases in total mortality and mortality due to coronary heart disease. Beta blockers, agents that are used to decrease heart rate, have proven quite effective in decreasing mortality rates after heart attack. Remarkably, the magnitude of the decrease in mortality is directly proportional to the magnitude of heart rate reduction.

     What does all this mean? Is there really a magical number of heart beats and then our time is up? Not quite.

     However, our heart rate is one of the most sensitive early markers of the effects of stress, a sort of canary in the coal mine. By stress I mean any environmental (eg. pollution), psychological (eg. living with a sick family member or difficult job situation), or biological (eg. elevated blood pressure or blood sugar or inflammation) phenomenon that impairs health. Such stressors affect the system that controls heart rate. Therefore changes in that system provide one of the earliest measureable signals in the development of disease.

     To give you an idea of the exquisite sensitivity of heart rate measurements in revealing early disease, I'll give you some startling examples.

     As an individual's blood sugar readings creep up, but before leaving the normal range, indicating the start of a process where insulin sensitivity is decreasing, there are characteristic changes in heart rate testing. The same is true of rising cholesterol levels, blood pressure and body weight.

     In other words, simple noninvasive heart rate tests can be more sensitive and provide observable changes earlier than blood testing. As importantly, certain exercises can reverse these changes and prevent the onset of illness. First let's give you the background for this physiology.

     In order to understand how heart rate is affected by stressors, we need to review that part of the nervous system that is responsible for adjusting our pulse in response to these cues. Unlike the voluntary nervous system which sends messages from brain to muscle so we can move about, the autonomic nervous system directs the "support functions" so to speak. It changes circulation so you don't pass out when you jump out of bed, raises your heart rate when you run for the bus, and brings it back to a resting rate when you get to your seat on the bus. This branch of the nervous system was called "autonomic" because it was thought to be automatic, requiring not only no thought, but no input from higher neural centers in the brain (not so). The heart and vasculature, lungs, stomach, liver, pancrease, spleen, and gastrointestinal tract are all regulated by the autonomic nervous system thereby controlling digestion, heart rate, blood pressure and many other essential functions.

     This part of the nervous system acts through two separate, opposing and therefore alternately activated, subsystems, the sympathetic and parasympathetic branches. The "fight or flight" response is orchestrated by the sympathetic division and the parasympathetic division oversees such things as digestion, energy storage, and growth and repair, sort of peace time activities.

     This set up has worked brilliantly, beautifully fine tuned by millions of years of evolution. It has allowed countless zebra to escape the lions' claw as well as primates like us to kill and not be killed, grow and reproduce. So what changed? How did this system designed to get us through stressful situations become maladaptive?

     The environment in which evolution crafted our nervous system provided short-lived stressors. A predator approaches, you run, you escape or you're eaten. This scenario might have lasted 10-15 minutes.

     Contrast that with typical contemporary stress. You wake up after a night of insufficient sleep because you were anxious about the presentation today that will determine a promotion and the colleague competing for the position is the brother-in-law of your boss, completely incompetent, but will probably beat you on this one, and you could really kill him, not only because he's an idiot and drives you crazy, but because your daughter is about to start college and chose the private (read unaffordable) school over the state one your son attends where you just found out he is on academic probation. You see my point.

     Put simply, ongoing stress is a recent invention. And our response to it makes us sick. The epidemic prevalence of stroke, heart attack, obesity, stomach ulcer, irritable bowel syndrome, chronic fatigue syndrome, depression and anxiety, insomnia, infertility, compromised immune function and accelerated aging is largely due to chronic stress.

     In my next entry I will speak about how we can prevent these maladies through interventions that directly repair the imbalance that chronic stress causes in the autonomic nervous system.