What is relative humidity and how does it affect how I feel outside?

If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

Karl Weatherly/Getty Images

Humidity is somethi­ng we hear about daily in weather reports. Humidity is to blame for that muggy, steam-room feeling you experience on certain summer days.

Humidity can be measured in several ways, but relative humidity is the most common. In order to understand relative humidity, it is helpful to first understand absolute humidity.

Sudden Cardiac Death: Are You at Risk?

Source: Article first appeared in "Know Your Man Inside Out" by SingHealth / Her World

Did you know?

Heart attacks are not confined to the old. Even young men can get a heart attack leading to sudden death.  80 per cent of all sudden cardiac death are related to coronary heart disease which, in most cases, can be prevented.

What causes young men to die suddenly?The most common cause is sudden cardiac death (SCD), of which 80 per cent is related to coronary artery disease (CAD) (see box below), with or without a heart attack.

Unfortunately, over half of sudden cardiac death victims have no prior symptoms. Some patients have chest pain, breathlessness or sweating. When these occur in a patient at risk of heart problems, treatment should always be sought immediately.

An SCD attack is not the same as a heart attack. SCD is caused by an abnormal heart rhythm due to an abnormal ‘electrical circuitry’ of the heart. A heart attack is caused by blockage of the arteries supplying blood to the heart. The subsequent damage to the heart muscle may or may not lead to an SCD attack. It is estimated that 1,000 Singaporeans die from SCD every year, about half of whom are below 60 years old.

Learn to recognise these symptoms

• Central or left-sided chest pain often associated with sweating, nausea or breathlessness. The pain is described as something weighing heavily on the chest and is usually brought about by physical or emotional stress. It usually goes away within minutes when the stressful activity is stopped.

• Shortness of breath. Because the heart muscles are damaged by the shortage of blood supply or from a heart attack, it can’t pump blood efficiently to meet the body’s needs.

• Discomfort on exertion, jaw tightness on exertion or after meals. These symptoms immediately subside on resting.

In anyone at high risk for heart disease (eg diabetics, high cholesterol, hypertension, strong family history of heart disease), any chest symptom, even atypical, should be investigated. Diagnosis is made with an electrocardiogram and blood tests.

Treatment may involve hospitalisation and ways to restore blood flow in the coronary artery (by angioplasty or thrombolysis).

If you are around...

1. Call the ambulance immediately. Early treatment increases survival rate.

2. Perform chest compression CPR. This will also improve the chances of survival.

Cardiac Artery Disease (CAD) CAD is a common type of heart disease where fatty deposits accumulate in the coronary artery and impede the blood flow. Reduced blood flow to the heart can cause chest pain (angina). A sudden, complete blockage can lead to a heart attack. Many people who have this form of heart disease are not aware they have it. CAD develops slowly and silently over decades. It can go virtually unnoticed until it produces a heart attack. You can prevent or slow down CAD by taking steps to improve your heart health. Drugs and surgical techniques can open up narrowed coronary arteries, but the best long-term solution is to make the right lifestyle choices.

Are You in the High-Risk Group?Age: Age increases a person’s susceptibility to heart disease. Gender: Men are three to five times more likely to have coronary heart disease than women. However, the risk for women increases after menopause. Five to 10 years after menopause, women have the same risk for coronary heart disease as men. Ethnicity: Compared with Chinese, South Asians (Indians, Sri Lankans, Pakistanis, etc) are three times more likely to suffer from coronary heart disease. Malays have double the risk compared with Chinese. Obesity: People who have excess body fat – especially located around the waist – are more prone to heart disease and stroke even if they have no other risk factors. Excess weight increases the strain on the heart. It also raises blood pressure, blood cholesterol and triglyceride levels, and lowers HDL, ("good" cholesterol levels). It is also associated with the development of diabetes mellitus. Family history: You can be at higher risk of heart disease if your immediate family members (parents, children, brothers and sisters) have a history of premature heart disease. Certain risk factors tend to run in some families. If there is a history of heart disease in your family, you should try very hard to control your other risk factors. "In general, adults should know their family history of heart disease or sudden death. They should know their cholesterol level and know if they have diabetes mellitus and abnormal blood sugar levels. If you have any high-risk factor, get your doctor’s advice on how to improve those risk factors, change your lifestyle and dietary habits, and embark on a safe exercise programme."  Dr Teo Wee Siong, Senior Consultant Cardiologist, National Heart Centre http://www.healthxchange.com.sg/healthyliving/SpecialFocus/Pages/Sudden-Cardiac-Death-Are-You-at-Risk.aspx?