Age-related surgery risk

A news item appeared this week citing mortality and morbidity statistics for patients who undergo abdominal surgery.  This led me to probe a bit into how surgery risks increase with age and even to speculate on why. 

First of all, to be clear on terminology, morbidity relates to ongoing disease, sickness or poor health and mortality describes the probability of death, usually measured in numbers of death per thousand individuals.  Both are cause-independent, that is, if mortality connected with  cancer surgery is counted in terms of deaths in the year following the operation, deaths due to pneumonia, stroke or other causes would be counted along with deaths due to cancer.  Comorbidity refers to the presence of one or more additional diseases or disorders, such as pneumonia and hypertension going along with lung cancer. 

In the latest study Impact of advancing age on abdominal surgical outcomes “Nader N. Massarweh, M.D., and colleagues at University of Washington School of Medicine, Seattle, examined complication and death rates of 101,318 adults age 65 or older who underwent common abdominal procedures such as cholecystectomy (gall bladder removal), hysterectomy and colectomy from 1987 to 2004. Complications were recorded within 90 days of discharge and deaths were recorded within 90 days of hospital admission(ref).” 

A review of the publication states:  “Older adults have a higher risk of complications and early death after common abdominal surgeries than doctors thought, a new study found.”

“Among patients 65 and older, the 90-day complication rate after abdominal surgery was 17.3% and the 90-day death rate was 5.4%, according to an online report in the Dec. 21 Archives of Surgery.”

“The likelihood of complications increased as patients aged beyond 65 years, with the researchers finding the following associations between age and complication frequency (trend test, P<0.001):

• 65 to 69 years, 14.6%
• 70 to 74 years, 16.1%
• 75 to 79 years, 18.8%
• 80 to 84 years, 19.9%
• 85 to 89 years, 22.6%
• 90 and older, 22.7%

Similarly, older patients were at higher risk of mortality. Death rates by age group were (trend test, P<0.001):

• 65 to 69 years, 2.5%
• 70 to 74 years, 3.8%
• 75 to 79 years, 6.0%
• 80 to 84 years, 8.1%
• 85 to 89 years, 12.6%
• 90 and older, 16.7%”

“Among older adults, the risk of complications and early death after commonly performed abdominal procedures is greater than previously reported,” Nader N. Massarweh, MD, of University of Washington School of Medicine, Seattle, and colleagues concluded(ref).”  What I find interesting is the rapid acceleration of death rates with age.  Comparing the 65-69 range with the 85-89 range, over a 20 year age interval the death rate associated with a surgery has gone up by a factor of five.

Reading this report led me to wonder if the reported  magnitudes of increase in risks with advancing age are typical or whether they are unique to the kinds of surgery studied.  So, I set out to look for other large scale studies of age-related morbidity and mortality associated with different surgical procedures.  One such study is reported in the 2005 paper Early mortality among Medicare beneficiaries undergoing bariatric surgical procedures.  “Results:  A total of 16,155 patients underwent bariatric procedures (mean age, 47.7 years [SD, 11.3 years]; 75.8% women). The rates of 30-day, 90-day, and 1-year mortality were 2.0%, 2.8%, and 4.6%, respectively. Men had higher rates of early death than women (3.7% vs 1.5%, 4.8% vs 2.1%, and 7.5% vs 3.7% at 30 days, 90 days, and 1 year, respectively; P<.001). Mortality rates were greater for those aged 65 years or older compared with younger patients (4.8% vs 1.7% at 30 days, 6.9% vs 2.3% at 90 days, and 11.1% vs 3.9% at 1 year; P<.001).   After adjustment for sex and comorbidity index, the odds of death within 90 days were 5-fold greater for older Medicare beneficiaries (aged 75 years; n = 136) than for those aged 65 to 74 years (n = 1381; odds ratio, 5.0; 95% confidence interval, 3.1-8.0).”  Normally, the risk of death associated with bariatric surgery is low (0.5%), but apparently the risk rises very steeply with advanced age, much as observed in the first-mentioned study.

Both of the above studies were concerned with surgeries of the GI track.  Turning to a different kind of operative procedure the report Coronary arteriography and coronary artery bypass surgery: morbidity and mortality in patients ages 65 years or older. A report from the Coronary Artery Surgery Study, ‘Of 2144 patients age 65 years or older entered into the registry of the Coronary Artery Surgery Study (CASS) who had coronary arteriography, 1086 underwent isolated coronary artery bypass grafting. Complications of angiography included death in four patients and nonfatal myocardial infarction in 17. Eight patients suffered neurologic complications, which were transient in five. The perioperative mortality was 5.2% (57 of 1086), which is significantly greater than the perioperative mortality of 1.9% (151 of 7827) in patients younger than 65 years entered in CASS (p less than 0.001). There was a trend toward an increased mortality rate with age; it was 4.6% (37 of 803) in patients age 65-69 years, 6.6% (16 of 241) in those 70-74 years and 9.5% (four of 42) in those 75 years or older. The duration of hospital stay after operation was significantly longer for the patients 65 years or older than for the patients younger than 65 (13.3 vs 11.4 days; p less than 0.001).”  Again, the observed increase of mortality with age was drastic and consistent with that reported in the other studies.

I checked out one more study Effect of patient age on increasing morbidity and mortality following urogynecologic surgery.  “There were 264,340 women in our study population. Increasing age was associated with higher mortality risks per 1000 women (<60 years, 0.1; 60-69 years, 0.5; 70-79 years, 0.9; ≥80 years, 2.8; P < .01) and higher complication risks per 1000 women (<60 years, 140; 60-69 years, 130; 70-79 years, 160; ≥80 years, 200; P < .01). Using multivariable logistic regression, increasing age was associated with an increased risk of death (60-69 years, odds ratio [OR] 3.4 [95% CI 1.7-6.9]; 70-79 years, OR 4.9 [95% CI 2.2-10.9]; ≥80 years, OR 13.6 [95% CI 5.9-31.4]), compared with women <60 years. The risk of peri-operative complications was also higher in elderly women 80 years of age and older (OR 1.4 [95% CI 1.3-1.5]) compared with younger women.”  Again, a similar pattern was observed, 5.6 times he mortality risk in the oldest group compared to that that in the younger group.  Amazing how similar these rates are to those observed in the first-mentioned study above, and amazing the difference that 20 years makes at the end of life! 

These results are not surprising given what we know about aging.  Vulnerability to multiple causes of illness and death starts to accelerate around 50, picks up in the 60s, accelerates further in the 70s and goes into warp overdrive in the 80s – resulting in everybody in known history being dead by age 123.  There are many ways to explain this effect, the 14 theories of aging and seven candidate theories in my treatise being the main ones from a scientific viewpoint.  The darkest view is that given in my blog entry Homicide by DNA methylation.   According to that view, lifelong progression of DNA methylation causes accumulation of irreversible DNA mutational damage.  Even if you could reverse the methylation at old age you could not undo the mutations so its soon curtains for us old folk, no matter what.  End of discussion.  The other theories of aging to some extent allow more hope for the prospect of extending life.  Discovering where the best realistic hope lies is an ultimate objective I have in following and understanding the research described in this blog.