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The Great Cat Debate: indoor-only versus indoor-outdoor. We've all heard the claims—"outdoor cats only live 3-5 years!"—but what's the actual data?

A new study published in *PLOS One* (2022) analyzed 30 years of necropsy data from the UC Davis veterinary hospital, covering over 3,100 cats. Here's what the numbers actually say.

The Data Breakdown

| Lifestyle | Median Age at Death | Source | |-----------|-------------------|--------| | Indoor-only | 9.43 years | JFMS (UK study, 8,000 cats) | | Indoor-outdoor | 9.82 years | JFMS (UK study, 8,000 cats) | | Outdoor-only | 7.25 years | JFMS (UK study, 8,000 cats) | | Indoor (UC Davis) | ~10-15 years | General estimate |

The difference between indoor and outdoor cats was statistically significant (p=0.0001). But here's the nuance: the UK study found **indoor-outdoor cats had virtually the same lifespan as indoor-only cats**—the difference wasn't statistically significant.

What's Killing Outdoor Cats?

  • **Cancer:** 35-41% of deaths
  • **Kidney disease:** ~13%
  • **Heart disease:** ~10%
  • **Trauma:** Higher in outdoor cats (vehicle accidents, fights, predation)

Outdoor cats face unique risks that shorten their lives: vehicles, coyotes and predators, infectious diseases (FIV, FeLV), toxins, and parasites. A UC Davis study found outdoor-only cats had significantly shorter lifespans—but also noted the data likely underestimates outdoor cat mortality because some cats are lost and never found.

The Nuanced Take

  • Indoor-only cats: median ~9.4-15 years
  • Outdoor-only cats: median ~7 years

That's roughly a 2-3 year difference in median lifespan, not 10 years.

But here's what the studies consistently show: **indoor cats live longer, full stop.** The risk profile is real.

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What This Means for Cat Owners

  • Keep them indoors at night (highest risk period)
  • Consider supervised outdoor time in a secure enclosure
  • Always spay/neuter (intact cats roam more)

The oldest cat on record—Crème Puff—lived to 38 years old. She was an indoor cat.

The Bottom Line

The real gap is 2-3 years median, not 10. Indoor-outdoor cats = indoor cats for lifespan. Keep cats indoors at night, use secure enclosures, and spay/neuter to reduce roaming.

Sources: PLOS One (2022)