The analysis in the Nov. 16 editorial "Exercise Economics" would not pass muster at the Office of Management and Budget. While the editorial finds that the equivalent of 195 days of intensive exercise, spread over 12 years, buys about 1.5 years of life when discounted at 3 percent, the OMB requires that the future benefits of proposed regulations be discounted at 3 percent and 7 percent; proposed regulations have to clear both hurdles. Applying a discount rate of 7 percent to the editorial's other data, one finds that the equivalent of 195 days of intensive exercise buys only an extra 178 days of life.

No wonder that so few sensible public health investments get past the OMB.

BENJAMIN COHEN

Bethesda

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Rob Stein's Nov. 15 front-page article, "A Daily Workout Could Add 4 Years to Life, Study Says," reported that moderate daily exercise can add several years to a person's life expectancy.

But at 30 minutes a day, five days a week, the average adult would spend 287 days of his or her life exercising, but add as little as 475 days to his or her lifespan. I'm not interested in giving up 21/2 hours of my leisure time every week now for a net gain of 188 days at the end of my life.

Doctors may be able to tell us how exercise will affect our health, but they have no business telling us that we should value those 188 days more than whatever happiness we gain now from spending time doing things we actually enjoy.

AMY PHILLIPS

Washington