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Archive for July, 2011

An open population differs from a closed population in that the population at risk is open to new members who did not qualify for the population initially. An example of an open population is the population of a country. People can enter an open population through various mechanisms. Some may be born into it; others may migrate into it. For an open population of people who have attained a specific age, persons can become eligible to enter the population by aging into it. Similarly, persons can exit by dying, aging out of a defined age group, emigrating, or becoming diseased (the latter method of exiting applies only if first bouts of a disease are being studied). Persons may also exit from an open population and then re-enter, for example by emigrating from the geographic area in which the population is located, and later moving back to that area.

The distinction between closed and open populations depends in part on the time axis used to describe the population, as well as on how membership is defined. All persons who ever used a particular drug would constitute a closed population if time is measured from start of their use of the drug. These persons would, however, constitute an open population in calendar time, because new users might accumulate over a period of time. If, as in this example, membership in the population always starts with an event such as initiation of treatment and never ends thereafter, the population is closed along the time axis that marks this event as zero time for each member, because all new members enter only when they experience this event. The same population will, however, be open along most other time axes. If membership can be terminated by later events other than death, the population is an open one along any time axis.

By the above definitions, any study population with loss to follow-up is open. For example, membership in a study population might be defined in part by being under active surveillance for disease; in that case, members who are lost to follow-up have by definition left the population, even if they are still alive and would otherwise be considered eligible for study. It is common practice to analyze such populations using time from start of observation, an axis along which no immigration can occur (by definition, time zero is when the person enters the study). Such populations may be said to be “closed on the left,” and are often called “fixed cohorts,” although the term cohort is often used to refer to a different concept, which we discuss in the following.

By Lauren Streicher, MD

The most frequent reason to stay home from work is not the flu, bad period cramps, a headache or even a hangover. Forty percent of all time off work, 23 million lost days and 3.5 million lost dollars are a direct result of the common cold. Runny nose, cough, stuffy head. No wonder a multimillion-dollar industry has evolved to treat, prevent and shorten the course of the misery. The question is, how many of those over-the-counter products actually do anything?

Myth #1: Taking vitamins and zinc lozenges will make a cold go away quicker.

While some studies show that zinc lozenges taken every 2 hours during the first day of symptoms are beneficial, most studies are inconclusive. Likewise, no study consistently proves that vitamin C in orange juice, or any other vitamin or herb for that matter, will prevent a cold, or make an existing cold go away faster. Keep in mind that the profit-motivated companies that manufacture and distribute herbs and vitamins are non-FDA approved, and are not required to prove efficacy. They can, and do, say whatever they want to promote their product.

Myth #2: Echinacea prevents colds.

Echinacea was originally used by Native Americans to treat burns and snakebites. Today, retail sales for echinacea to treat and prevent the common cold top $40 million annually. Unfortunately, since it has never been proven in good scientific studies to make a difference beyond the placebo affect, the only ones who benefit from echinacea are the companies that sell it.

Myth #3: You’re more likely to catch a cold on an airplane than in someone’s house.

There is no evidence that recirculating air on a plane increases the likelihood of transmitting a cold. Jamming 3 people in a space meant for 2 and practically sitting on someone’s lap who is coughing and sneezing is another story. Your best bet is to upgrade to first class and bring extra tissue for your seatmates. Alcohol-based hand rubs are a good alternative when there is limited access to soap and water.

Myth #4

A certain effervescent vitamin supplement will reduce the chance that you will catch a cold even if you are surrounded by sneezers and coughers.

There is a reason that this product is not FDA approved. The manufacturers of this supplement used to advertise that it could prevent or cure the common cold, despite the lack of any real clinical evidence for such claims. In 2008, a suit was filed for false advertising, resulting in a $23.4 million class action settlement. Though it is now marketed as nothing more than an immunity booster, many people still think it will prevent or help cure a cold. If you are going to spend time in a room with sick people, better to spend your money on antiseptic hand gels and plenty of tissue.

There is one more myth I feel compelled to dispel. Despite what your mother told you, kissing is not the easiest way to transmit a cold. The virus responsible for colds doesn’t live in saliva, so even tongue-to-tonsil kissing doesn’t spread infection.

It’s sneezing, coughing, and breathing that transmits droplets filled with virus particles. In addition, the virus can live on skin for 2 hours, so if you shake someone’s hand and then touch your eyes, nose or mouth, you can become infected. Hand washing is actually the #1 way to prevent transmission of the virus. So feel free to kiss your ailing honey as long as he doesn’t shake your hand or breath on you.

By Lauren Streicher, MD

Everywhere you turn, there are articles and advertisements touting the benefits of robotic surgery, so it’s no surprise that my patients routinely ask if their scheduled hysterectomy will be performed using a robot. But who really benefits from robotic surgery? Contrary to hype, it may not always be the patient.

Robotic surgery is a minimally invasive technique (i.e. uses tiny incisions) that was originally developed as a way to operate on wounded soldiers who couldn’t get to an expert surgeon. With robotics, the surgeon can operate remotely, sitting at a console miles away and moving levers to control the robots “arms” and maneuver instruments, which are placed into the patient by an on-site surgeon.

While robotic surgery was originally designed to be performed from a distance, most robotic surgery is currently performed with the primary surgeon sitting at a console in the same room as the patient, and a second surgeon standing in the traditional spot next to the patient. Robotic instruments can do things traditional laparoscopic instruments cannot, like twist, turn and maneuver around corners. In addition, the technology allows the surgeon to have a magnified 3-D perspective, almost like standing inside the body while operating. The result is the ability to see and do things that can’t be done otherwise. In the event that a procedure can’t be completed robotically and an incision needs to be made, both surgeons are in the room and can proceed.

So what’s the down side?

The benefits of robotic hysterectomy are clear when being performed in order to avoid an abdominal incision. But, if a robotic surgery is being offered to replace a laparoscopic hysterectomy, another minimally invasive method, the advantage has not been established. The truth is that, in most cases, laparoscopic surgery usually has all the benefits of a robotic surgery, but with a much lower price tag. Whether a hysterectomy is performed robotically or laparoscopically, the patient has minimal pain and a speedy recovery. Complication rates are the same in experienced hands.

If a laparoscopic procedure is not possible and a traditional abdominal incision is the only option, that’s where robotics comes in and is truly beneficial. This is typically the case if someone has cancer, a lot of scar tissue, or a very large uterus so even skilled laparoscopic surgeons can’t get the visualization they need to do highly technical work. In these cases, the result of using robotics is shorter operating times, less blood loss, fewer complications, and much shorter recoveries (assuming your surgeon is skilled and very experienced at doing robotic surgery). However, if your doctor says your surgery can be safely performed laparoscopically, there is likely no benefit (beyond the “cool factor”) to a robotic procedure.

While few hospitals currently own the very expensive equipment that is required to perform robotic hysterectomies, many are expected to offer this new procedure within the next few years. If it is no better, safer or more cost effective than a laparoscopic hysterectomy, why is this happening? The answer is easy: marketing. Patients want the newest and most high-tech methods, even if the benefits have not been established. Hospitals and doctors get paid the same thing whether a hysterectomy is performed laparoscopically or robotically, but hospitals that don’t offer robotics are worried that patients will simply take their uteruses elsewhere.

Every year 600,000 hysterectomies are performed, but only 15% are performed using a minimally invasive technique. Expert laparoscopic surgeons are able to perform roughly 80% of hysterectomies laparoscopically without a robot. To me, it makes far more sense to train surgeons to become expert laparoscopic surgeons than to buy million-dollar robots to do what can be done using far less expensive instruments.

This is a controversial area and there are gynecologic surgeons who will disagree with me. But the scientific literature has not yet shown a benefit to robotic surgery over laparoscopic surgery for non-cancer hysterectomies. More studies are needed. I am currently participating in such a study comparing patient outcomes in traditional laparoscopy vs. robotic surgery … so stay tuned.

For more information on laparoscopic hysterectomy and alternatives to hysterectomy, check out my book, The Essential Guide to Hysterectomy.