Body mass index (BMI) and waist circumference are both useful measures for assessing your weight status in relation to potential disease risk. Our risk algorithms use BMI.
Q. Why are potatoes and fruit juice “bad” and vegetables are “good”?
A. It is not necessarily that potatoes are unhealthy, but that high potato consumption is seen in people whose diet is less healthy than others. Our study, like many others, found an association between greater consumption of potatoes or fruit juice and unhealthy outcomes.
Q. Why don’t the diet questions take into account fat, sugar, meat, dairy, etc.?
A. Our calculator uses fruit and vegetables as a broad measure of diet quality. Our biggest constraint is the underlying data that we use to generate our risk algorithms that only had six brief diet questions. However, like many other studies, we found that there is a strong link between fruit and vegetable consumption and health outcomes. We hope to update the calculator in the future to include more details about diet.
Q. None of the physical activities I participate in are listed in your calculator so how can I assess my physical activity?
A. We have divided the physical activity questions into three intensity groups and provided examples that reflect the typical energy cost of the activities. Vigorous-intensity activities are those that require a large amount of effort and cause rapid breathing and a substantial increase in heart rate (i.e., you can’t talk or your talking is broken up by large breaths). Moderate-intensity activities require a moderate amount of effort and your heart beats faster than normal – (i.e., you can talk but not sing). Light activities cause your heart to beat slightly faster than normal (i.e., you can still talk and sing). If your activity isn’t listed, assess the level of intensity based on the above descriptions and add your hours to the appropriate group.
Q. I am a male, why doesn't my physical activity change my cardiovascular disease risk?
A. Physical activity is an important contributor to cardiovascular disease risk (i.e., there is a causal relationship). However, the Project Big Life Heart Attack & Stroke calculator is a predictive model—it predicts the chance of future occurrence of cardiovascular disease. The goal of a predictive model is to get the best prediction based on a combination of variables. For males, physical activity was associated with other variables that are more predictive of cardiovascular disease, so physical activity dropped out of the model.
Q. What is the difference between causation and prediction?
A. The goal of a causal study or model is to determine whether an exposure really causes an outcome or to estimate how big is the effect. For example, a casual model answers the question: how much of your cardiovascular disease risk is due to your smoking? The goal of a prediction model is to develop a formula for making predictions about the future occurrence of an outcome based on various exposures. Given our example, a predictive model answers the question: what is your probability of developing cardiovascular disease given you are a smoker? Sometimes risk factors that are strongly causal of a disease have low capacity to determine who will or won't develop the disease. For example, physical inactivity increases cardiovascular disease risk, however, it does not predict which men will or won't develop cardiovascular disease beyond the other variables in the Project Big Life Heart Attack & Stroke calculator.
Q. Why does it seem like you don't take BMI into account in determining expected life expectancy?
A. BMI is included but we only report the impact of more “upstream” risk factors - diet and physical activity - which lead to the intermediate risk factors (e.g., obesity) and health outcomes. Taking this into account, only very high BMI affects life expectancy.
Q. Why does the calculator not include questions about [x] disease?
A. Currently, we don't have data to provide more accurate estimates for people with a history of all diseases. As well, diseases like cancer are really a collection of more specific diseases (i.e., lung cancer, breast cancer) that may have different mortality risks. We are hoping to include more specific disease in future updates. However, we hope that you will still find the calculations helpful. Healthy living is important for people with chronic diseases.
Q. How important is healthy living to how long you will live?
A. Extremely important. We emphasize healthy living (what you eat, how active you are, whether you smoke, etc.) for two reasons. First, there is a very wide range in future health based on current healthy living. For example, based on Project Big Life calculators, life expectancy for a 20-year old differs by 18 years (see paper here) depending on their healthy living profile. Second, healthy living is something that can be modified.
Notice that we used "modify", instead of saying "something you can change yourself". Almost everyone strives to improve their healthy living but too often the healthy choices are not the easy choices. We hope that Project Big Life will help inform the importance of making your entire community a healthy place to live.
Q. Where do the target recommendations come from?
A. Physical activity: Canadian Physical Activity Guidelines www.csep.ca
Fruits and Vegetables: Canada’s Food Guide www.hc-sc.gc.ca
Alcohol: Canadian Centre on Substance Abuse Low-Risk Alcohol Drinking Guidelines www.ccsa.ca
Smoking: Health Canada Tobacco Scientific Facts www.hc-sc.gc.ca
Body Mass Index: Canadian Guidelines for Body Weight Classification in Adults www.hc-sc.gc.ca
Air Pollution: There are no well-established targets for Canada. We calculate your life expectancy lost from air pollution as the excess mortality above the 25th percentile Canadian exposure. These levels are: 6.0 ppb Nitrogen dioxide (NO2); µg/m3 6.0 ug/M3 for articulate matter (PM2.5); 34.3 for ppb Ozone (O3)."