The time may not be far off when more adults need diapers than babies as the population grows older, potentially a huge opportunity for manufacturers of incontinence products — if they can lift the stigma that has long constrained sales.

The market for adult diapers, disposable underwear and absorbent pads is growing fast, up 9 percent last year to $9 billion, having doubled in the last decade, according to Euromonitor.

But manufacturers like market leaders Essity and Kimberly-Clark Corp. reckon only half of the more than 400 million adults likely to be affected by weak bladders are buying the right products, because they are too embarrassed.