Does the Risk of Surgery Increase with Age
Shabbir M.H. Alibhai, MD, MSc, FRCP(C)
Staff Physician, University Health Network,
Instructor, University of Toronto,
Toronto, ON.
The last few decades have seen major advances in the surgical management of numerous illnesses. As the proportion of the elderly in the general population continues to increase, the prevalence of many chronic conditions also increases. Given the number of available surgical therapeutic options to cure or palliate these chronic conditions, more and more elderly patients are undergoing surgery. Conventional wisdom suggests that, compared to younger or middle-aged patients, older individuals have a higher risk of perioperative and postoperative complications, including death. This increased risk has been attributed to aging itself. This article will examine this relationship in greater detail.
Dozens of studies have suggested that advanced age leads to an increased risk of experiencing surgical complications. This includes an increased risk of postoperative complications such as deep venous thrombosis, infections (including wound, urinary tract, and lung), delirium and mortality.1 In preoperative assessment clinics, internists and anesthetists utilize risk indices or algorithms to determine an individual patient's surgical risk and potentially modifiable risk factors. Classic indices like the Goldman Index2 or Detsky Index,3 which assign points to different conditions that increase perioperative risk, both include advanced age as a risk factor. Some, but not all of the more recent risk stratification protocols continue to include age as an independent risk factor.4-6
When considering these predictive models, it is important to ensure that adequate adjustments have been made for the presence of comorbid illnesses and functional limitations. Comorbidity, referring to coexisting illnesses that impact upon health, has been shown to be a powerful predictor of adverse outcomes. Not taking comorbidity into consideration when examining surgical risk could lead to erroneous conclusions. A classic example involves the treatment of benign prostatic hyperplasia (BPH). Both open and transurethral (TURP) approaches have been utilized. Some years ago, several articles were published suggesting that TURP is associated with a higher morbidity than is open prostatectomy.7 However, a later study was published that adjusted for comorbidity and found no increased risk with TURP.8 This suggests that sicker, frailer patients who needed surgical treatment of BPH were receiving TURP rather than open prostatectomy. While this may be intuitively obvious to clinicians, these articles demonstrated the importance of adjusting for comorbidity. Functional status, or degree of disability, has likewise been shown to be a powerful predictor of adverse effects,9 yet most studies on perioperative risk have made no attempt to measure this variable.
Recognizing the powerful influence of comorbidity and functional status, a number of carefully conducted studies have attempted to adjust for these variables. Several, but not all, of these studies have demonstrated a small but consistent contribution of advancing age to increased surgical risk, especially for major surgical procedures.10,11 Why might this be? Several factors that are putatively related to specific conditions are listed in Table 1. It should be recognized that these factors are possible explanations, often based on limited evidence. The various factors listed can be divided into two broad categories: (i) age-associated decline in organ function; and (ii) subclinical or clinically apparent coexisting disease. How much is contributed by each of these factors is an area of considerable controversy. In general, most experts argue that the majority of increased risk is explained by coexisting, often clinically unappreciated, illnesses rather than by aging itself.
Despite demonstrating that advanced age independently increases the risk of certain perioperative complications, including mortality, three important considerations make this observation of limited clinical relevance in isolation.
First, there have been significant improvements in perioperative management over the last few decades. Improvements