Activity intensity and all-cause mortality following fall injury among older adults: results from a 12-year national survey

Key points

1. 01None-to-low activity intensity was associated with a 50% increased adjusted mortality risk (aHR 1.50; 95% CI 1.20-1.87) compared to normal-to-high activity
2. 0281% of older adults with fall injuries reported none-to-low activity levels at baseline
3. 03Median survival was 8 years in the low-activity group versus 12 years in the normal-to-high group
4. 04The proportion of older adults with low activity declined from 90% in 2006 to 72% in 2017, but most remain insufficiently active
5. 0547% of deaths in the low-activity group were attributable to low or no physical activity

How it was conducted

Design

Retrospective cohort study using 12 years of pooled National Health Interview Survey (NHIS) data (2006-2017)

Participants

2,454 community-dwelling US adults aged 65 years and older who sustained a fall injury within 3 months of interview and were eligible for mortality follow-up

Activity classification

Binary: none-to-low (<500 MET-minutes/week) vs. normal-to-high (>=500 MET-minutes/week) based on self-reported leisure-time moderate and vigorous activity

Primary outcome

Time to all-cause death following fall injury, assessed via linkage to the National Death Index

Analysis

Survey-weighted Cox proportional hazard regression with multiple imputation for missing data; Kaplan-Meier and Nelson-Aalen curves generated

What they found

• None-to-low activity was associated with a 50% increased adjusted mortality risk (aHR 1.50; 95% CI 1.20-1.87)
• Unadjusted hazard ratio for none-to-low vs normal-to-high activity was 1.99 (95% CI 1.62-2.44)
• 45.3% of the sample died during follow-up (1,059 of 2,454)
• Mortality incidence rate was 8.5% in the none-to-low group vs 4.5% in the normal-to-high group (IRR 1.89; 95% CI 1.55-2.32)
• Median survival was 8 years in the none-to-low group and 12 years in the normal-to-high group
• Sensitivity analysis (three-level): no-activity aHR 1.46 (95% CI 1.15-1.83); low-activity aHR 1.69 (95% CI 1.29-2.22) vs normal-to-high
• Activity limitations were associated with a 2-fold adjusted mortality increase (aHR 2.00; 95% CI 1.66-2.41)
• Five or more chronic diseases associated with aHR 1.47 (95% CI 1.13-1.91)
• Poor self-rated health associated with aHR 2.07 (95% CI 1.68-2.54)
• Current smoking associated with aHR 1.50 (95% CI 1.13-1.99)

Limitations

• Observational design precludes causal inference; reverse causality is plausible because sicker individuals may be less active
• Physical activity was self-reported and subject to recall bias or under/over-reporting
• Important confounders were not available in the dataset, including injury severity, frailty index, cognitive function, depression, and medication use
• The chronic disease index was limited to 10 conditions, preventing use of validated comorbidity indices such as Charlson or Elixhauser

Why it matters

For patients

If you are an older adult who has had a fall, staying as physically active as safely possible may meaningfully reduce your risk of dying in the years that follow.

For clinicians

Routine assessment of physical activity levels in older patients after fall injury is warranted; those with low activity represent a high-risk group who may benefit from structured exercise referrals and counseling.

For readers

This large national cohort study adds evidence that low physical activity is independently associated with post-fall mortality, supporting activity promotion as a priority intervention for aging populations.