Leading disease-related deaths in the US (1999). Datasource: CDC.

According to the latest data from the US Centers for Disease Control and Prevention (CDC), even though heart disease and cancer still accounted for over half of all deaths in 1999, there was a 2% reduction in the numbers of mortality they caused compared with the previous year. This continues a downward trend for both diseases. However, more Americans are dying from diabetes (up by 3.3 %) and respiratory diseases (up by 4%), with the latter rise being sparked by two influenza outbreaks.

Increases were also seen in deaths due to septicemia (6.6%), hypertension (5%), while deaths due to HIV declined by 3.6%—a much smaller drop than was posted either of the last three years when the rate fell by 28.8, 47.7 and 20.6 % respectively. Life expectancy estimates at birth in 1999 remained the same as in 1998, 76.7 years.

Meanwhile, a 34-year long study has raised questions about just how much exercise improves health. A panel of leading exercise scientists concluded that an inverse and mostly linear relationship exists between physical activity and the rate of all-cause mortality, cardiovascular and coronary heart disease, type 2 diabetes and colon cancer. However, for many diseases the dose-response relationship is unclear based on a lack of, or contradictory, data.

I-Min Lee of Harvard Medical School, author of one of the articles published in the Medicine and Science in Sports and Exercise journal, says that for heart disease and all-cause mortality, benefit was shown at lower levels of activity but this decreases at higher levels.

The effect of exercise on heart attack, stroke and cardiovascular-related death is a major component of a new study in patients with type 2 diabetes. The National Institutes of Health's Look AHEAD (Action for Health in Diabetes) study will randomize 5000 overweight volunteers with diabetes to a program promoting weight loss via a low fat, low calorie diet and they will gradually increase their activity levels to 30-35 minutes of brisk walking for 5-6 days per week. Volunteers will be followed for up to 11.5 years, making this the first long-term study looking at the effect of weight loss and physical activity in diabetic patients.