For the first time in 45 years, homicide dropped out of the top 15 causes of death in the United States in 2010, according to a new government analysis of mortality trends.

Crime rates have been falling for decades, fueled by a range of social, demographic and law enforcement factors, but the just-released death figures from the National Center for Health Statistics underscore the decline.

“No one will believe you when you say assault is where it was in the 1960s,” said Gary LaFree, director of the department of criminology and criminal justice at the University of Maryland. “Homicide started to rise in 1963 and peaked in 1975.”

The 4.3 percent drop in assault deaths last year was part of a larger good-news trend that saw a slight increase in U.S. life expectancy -- now 78.7 years -- and declines in the age-adjusted death rates for seven of the 15 leading causes of mortality, including heart disease and cancer, according to preliminary figures.

Overall, the adjusted death rate fell to a record low of 746.2 deaths per 100,000 people, with a total of more than 2.4 million deaths. Hawaii was the state with the lowest mortality, with an adjusted rate of 589.6 deaths per 100,000 people. Mississippi had the highest death rate, 961.9 per 100,000 people.

Rates for five of the top 15 causes of death went up, including increases of 3.3 percent for Alzheimer’s disease and 4.6 percent for Parkinson’s disease.

“It’s the aging population,” said Dr. Roy N. Alcalay, an assistant professor of neurology at Columbia University Medical Center. “They’re not dying of these other diseases, so they’re dying from Alzheimer’s and Parkinson’s.”

Deaths from heart disease fell 2.4 percent, cancer deaths were down 0.6 percent, and deaths from chronic lower respiratory disease, stroke and accidents all fell by more than 1 percent.

Deaths from the bloodstream infection called septicemia fell by 3.6 percent and deaths caused by flu and pneumonia dropped a significant 8.5 percent.

“We’re doing a number of things right,” said Dr. William Schaffner, an infectious disease expert and chair of the department of preventive medicine at the Vanderbilt University School of Medicine.

Far fewer people died from influenza -- 494 deaths in 2010 vs. 2,918 in 2009 -- largely because of the impact of the H1N1 swine flu pandemic, which spared older people and led to widespread vaccination and immunity, Schaffner said.

“More people were protected,” he added.

Deaths from pneumonitis, or pneumonia caused by aspiration of bits of food, liquid or other substances, rose to 17,001 in 2010, up from 15,948 in 2009.

It’s not clear why those deaths jumped by 4.1 percent last year, said Dr. Norman H. Edelman, chief medical officer for the American Lung Association. Aspiration can be a complication of medical procedures, but it can be prevented by following basic precautions such as not eating for several hours before an operation.

That troublesome lung condition rose to become the 15^th top cause of death in 2010, bumping homicides out of that ranking for the first time since 1965.

LaFree, the Maryland criminologist, said there are several recognized factors that have led to the drop in violent assault deaths, including more people in prison, better law enforcement practices, the end of the crack cocaine drug epidemic of the late 1990s -- and the aging of a large swath of the population made up of the baby boom generation.

“I think that the key factor for crime going up is a legitimacy crisis,” said LaFree. “When people don’t think things are fair, they’re more likely to act out.”

Here are top five causes of death in 2010:

1. Heart disease

2. Cancer

3. Chronic lower respiratory diseases

4. Stroke

5. Accidents

To see the top 15 causes of death and the rest of the report, click here:

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