CHICAGO (AP) — As New Orleans residents warily track another threatening storm, a new report presents the clearest picture yet of deaths from Katrina in Louisiana. Of the nearly 1,000 who died, almost half were 75 or older, according to researchers.

Most died on the day of the storm — August 29, 2005 — and drowning was the leading cause of death. More than one-third died in homes.

The results present a tragic portrait of elderly residents who may have thought the warnings were a false alarm, who feared that abandoning their homes would lead to looting, or who simply didn't want to leave their familiar surroundings for the unknown.

The high death toll in the elderly was likely due to those factors along with older people being more vulnerable and frail and unable to fight the catastrophic storm, the report said.

The report provides the most comprehensive details yet of Katrina's deaths in Louisiana and "just shows us where we need to direct our disaster preparedness effort," said Joan Brunkard, the lead author and a researcher at the federal Centers for Disease Control and Prevention.

"We must reach these populations" before, during, and after storms, and provide the assistance and reassurance they need to be willing to evacuate, she said.

The study was published online Thursday and will appear in the October print edition of the journal Disaster Medicine and Public Health Preparedness.

"The findings in this report will aid public health and emergency preparedness efforts and may help reduce the mortality burden in future natural disasters," the researchers wrote.

Dr. Raoult Ratard, Louisiana's state epidemiologist and a co-author of the report, said plans are under way to help New Orleans' residents including the elderly prepare for the current storm, Gustav, which some projections say could hit Louisiana with hurricane strength in coming days.

"We're in the waiting period right now," Ratard said.

The new report focuses on deaths directly related to Katrina in Louisiana, and on deaths of Louisiana residents who fled to other states. It's based on death certificates listing Katrina as the main or contributing cause and data from a federal disaster response team. The researchers counted 971 Katrina-related deaths in Louisiana, mostly in New Orleans, and 15 deaths among residents who fled out of state.

The time period was Aug. 27 to Oct. 31, 2005, which includes deaths in car crashes on evacuation routes and from injuries suffered during the storm.

The previously reported death toll for all Katrina victims has been put at 1,698. That includes bodies collected in Louisiana, Mississippi and Alabama, and Louisiana residents who died in other states in the month after Katrina.

Among the findings:

— 40 percent of victims drowned.

— Just under half of all victims were 75 or older; the average age was 69.

— Only 2 percent were younger than 18.

— 51 percent were black; 42 percent were white.

Information on place of death was available for 877 victims; 36 percent died in homes, 22 percent in hospitals and 12 percent in nursing homes. More than 25 percent were found elsewhere, including the Superdome and Convention Center, where masses of people were housed during the storm.

After drowning, injury/trauma was the second-leading cause and accounted for about 25 percent of the deaths. There were four suicides and two slayings blamed on Katrina.

An editorial in the journal praises the report but says it likely underestimates the disaster's true toll because many more deaths were indirectly related to the storm.