THE DEATH RATES, fortunately, rarely make a splash in this country. But the pattern is well worth your attention as a basic indicator of American prosperity and health. The Public Health Service has just published the final figures for 1980, and preliminary data for 1982 are in hand. The 1980 numbers show a rise in the death rate that year. That has happened only twice recently and both times--the other was in 1968--for the same reason, a flu epidemic. Of all the causes of short blips off the long trend, influenza remains the most powerful. There's a tendency to assume that flu has been relegated to the status of a mere nuisance, controllable by drugs. That's not entirely true; it's still dangerous.

But the long trend, to which the numbers returned in 1981 and 1982, is downward and quite rapid. The basic reason is steady progress against the most common of all killers, the cardiovascular diseases--the broad category that includes heart trouble and strokes. Over the past 30 years, the cardiovascular death rate has dropped by one-third, by far the largest single explanation of Americans' longer lives. Of all deaths in this country, just under half are due to cardiovascular disease. The second most prevalent cause, cancer, accounts for a little over one-fifth of all deaths. All other contributors are, in the statistical sense, trivial by comparison. Accidents account for one out of 20 deaths, pneumonia and influenza in a normal year for one out of 40, and so forth.

Life expectancy for a newborn American in 1981, the most recent year for which it has been calculated, was just over 74 years. At the turn of this century it was 47 years--which is the present life expectancy in Bangladesh and the Sudan.

The life span in this country increased with great speed throughout the 1920s, more slowly in the 1930s, and fast in the 1940s. Then for two decades it hardly changed at all. In 1974, it began to move upward again. The explanations remain largely a matter of speculation, but the postwar slowdown seems to mark a period in which Americans got careless about their health and overestimated the help that doctors and clinical medicine could provide if they got sick. The turn in the mid-1970s came at about the time that a lot of people began listening more carefully to their doctors on the subject of preventive medicine, particularly regarding diet and exercise.

But it is a fair generalization to say that over the past century life expectancy has risen with national wealth. One thing that Americans have bought with their economic growth is longer lives. You are familiar with the argument that this country has spent too much of its vitality chasing dollars, and that Americans would be better people if they lived the simple, natural life. It's always useful to keep in mind the death rates associated with the simple, natural life. Americans have wasted some of their wealth, but by no means all of it. The current fall in the death rates suggests that, with a little more money and a little more wisdom, there is still much progress to be made.