The city’s overall death rate dropped to an all-time low in 2006 due in part to declines in mortality from HIV and smoking-related illness, the health commissioner said yesterday.

The number of deaths fell to 55,391 in 2006 from 57,068 a year earlier, according to the city’s Department of Health and Mental Hygiene. The only leading killer that increased significantly was substance use, up 8%.

Heart disease and cancer remained the most deadly, claiming 21,844 and 13,116 lives, respectively.

Between 2005 and 2006, death from HIV fell almost 15%, from 1,419 to 1,209, reflecting the lowest numbers since 1984 when 952 deaths from AIDS were recorded citywide.

Researchers attributed the decline to lower infection rates because of syringe exchange programs, expanded HIV testing, and slower disease progression.

HIV mortality remains concentrated among the city’s minority populations, with roughly 34% of deaths among black men; 21% among black women; 11% among white men; and 3% among white women.

New HIV diagnoses have recently increased among young men who have sex with men, but the trend has yet to affect mortality rates.

All smoking-related deaths dropped 11.2% between 2002 and 2006, from 8,722 to 7,744. The figures do not include deaths from exposure to second-hand smoke. The report also showed that life expectancy for women between 2004 and 2005 rose by 2.5 months to 81.3 years, while male life expectancy remained unchanged at 75.7 years.

Overall life expectancy rose to 78.7 years from 78.6 years.