An "exciting" improvement in Americans' health in the last decade was reported yesterday by the National Center for Health Statistics, the government's health-measuring agency.

The health of men has improved dramatically, and that of women also is better, the center told the Senate Health Subcommittee, which had asked it for a report on "the state of the nation's health."

The center reported a marked decline in death rates from heart disease and cancer, a drop in deaths from accidents and a recent drop in the death rate of men aged 25 to 74, called "particularly noteworthy becacuse it is a marked change in trend."

There is still "a long way to go," however, Dorothy P. Rice, the center's director, testified.

Among the bad news, she said, are an increase in suicides over the past 25 years and a "startling" increase in lung cancer death rates since 1950.

There was an especially sharp increase in lung cancer in women during this period when, Rice said, they have "unfortunately" come a long way'" as cigarette users.

The center said women have suffered a steady increase in breast cancer death rates since 1950, though this increase may have leveled off recently. The breast cancer death rate actually dropped a bit between 1974 and 1975.

Women are nontheless living almost eight years longer than men, on the average. Based on 1975 figures life expectancy at birth is now 63.7 years for men and 76.5 for women, the center said.

Life expectancy for whites was 73-2 years, but for all other groups it was 67.9, more than five years' difference the report said.

In the six years between 1969 and 1975, death rates for men aged 55 to 64 dropped 12 per cent, Rice reported.

She also noted a "dramatic" recent decline in U.S. infant deaths, though some other industrialized countries still do better. Sweden had a 1974 infant death rate of 12 per 1,000 live births compared with this country's rate of 16.7.

The United States still ranks 19th among nations in male life span and ninth in female. Rice said, health authorities usually ascribe part of the disparity to different ways of repporting death and disease, but more of it is due to this nation's sharp contrast between rich and poor and the persistence of large ill-educated, ill-housed and chronically unemployed popluations.

Social conditions, asay health authorities, affect health far more than medical care. Rice pointed out that the improvements in Americans' health have come during a period of many advances in medical treatment.

Still, she said, disease continues to cause much misery and economic loss, people with mental disorders, including retardation an senility, clog mental hospitals and nursing homes and account for the largest number of patient days in all institutions, she said.

Sen. Edward M. Kennedy (D-Mass.), Health Subcommittee hairman, said the country must begin to examine its health statistics so it can intelligently spend its health dollars.