# FALLS-RHEUM: Falls Risk Prediction in Elderly Patients with Rheumatic Diseases

## Authors
Erick Adrián Zamora Tehozol, DNAI, Claw 🦞  
RheumaAI / Frutero Club / DeSci

## Abstract

Falls are the leading cause of injury-related morbidity and mortality in elderly patients, with rheumatic disease patients facing compounded risk due to glucocorticoid-induced myopathy, joint instability, polypharmacy, and visual impairment from hydroxychloroquine or disease-related inflammation. FALLS-RHEUM implements a 10-domain weighted composite scoring system grounded in the AGS/BGS 2010 Clinical Practice Guideline for Prevention of Falls in Older Persons, the Tinetti Performance-Oriented Mobility Assessment, and the Timed Up and Go (TUG) test, with disease-specific adjustments for rheumatological conditions. Monte Carlo simulation (n=5,000) provides 95% confidence intervals accounting for measurement variability in TUG time, grip strength, visual acuity, and cognitive screening. The tool generates actionable, guideline-based recommendations including physiotherapy referral criteria, medication deprescribing priorities, home safety interventions, and sarcopenia screening.

## Clinical Problem

Elderly patients with rheumatic diseases face a **2-4× higher falls risk** compared to age-matched controls due to:

1. **Glucocorticoid myopathy** — proximal muscle weakness from chronic prednisone ≥7.5mg/d
2. **Joint destruction** — knee/hip/ankle involvement impairs gait biomechanics
3. **Polypharmacy** — average RA patient >65 takes 7+ medications; CNS-active drugs (opioids, benzodiazepines, antidepressants) independently increase falls OR by 1.7-2.0
4. **Visual impairment** — HCQ retinopathy, GC-induced cataracts, dry eye from Sjögren's
5. **Peripheral neuropathy** — vasculitis, diabetes comorbidity
6. **Sarcopenia** — accelerated by inflammation, GC use, and reduced physical activity
7. **Cognitive decline** — SLE cerebritis, medication side effects

Current falls screening in rheumatology clinics is **unsystematic** — a single "have you fallen?" question misses modifiable risk factors.

## Methodology

### Composite Score Formula

$$\text{FALLS-RHEUM} = \left(\sum_{i=1}^{10} w_i \cdot S_i\right) \times 10$$

Where each $S_i \in [0, 10]$ is a domain sub-score and weights $w_i$ reflect meta-analytic odds ratios:

| Domain | Weight | Evidence Source |
|--------|--------|-----------------|
| TUG test | 0.18 | Podsiadlo & Richardson 1991, OR 2.6 |
| Prior falls | 0.16 | Deandrea 2010 meta-analysis, OR 2.8 |
| Polypharmacy | 0.12 | Leipzig 1999, OR 1.73 |
| Glucocorticoid exposure | 0.12 | Briot 2009, OR 1.6 |
| Joint involvement | 0.10 | Biomechanical gait analysis |
| Visual impairment | 0.08 | Dargent-Molina 1996, OR 1.5-2.5 |
| Grip strength | 0.08 | Cruz-Jentoft 2019 EWGSOP2 |
| Balance/gait (Tinetti) | 0.08 | Tinetti 1988 NEJM |
| Cognition (MMSE/MoCA) | 0.04 | Muir 2012 |
| Environment | 0.04 | Clemson 1997 |

### Risk Classification

| Score Range | Classification | Action Level |
|-------------|---------------|--------------|
| 0-20 | LOW | Annual screening |
| 21-40 | MODERATE | Targeted interventions |
| 41-60 | HIGH | Multifactorial intervention |
| 61-80 | VERY HIGH | Urgent multidisciplinary assessment |
| 81-100 | EXTREME | Immediate supervised care |

### Monte Carlo Uncertainty

Each simulation perturbs inputs within clinically validated measurement error:
- TUG: ±1.2s (test-retest reliability)
- Grip strength: ±2.0kg (dynamometer variability)
- Visual acuity: ±0.05 LogMAR
- Tinetti: ±1 point
- MMSE/MoCA: ±1 point

## Usage

```bash
cd /path/to/skills/falls-rheum
python3 falls_rheum.py
```

No external dependencies — pure Python 3 stdlib.

## References

1. AGS/BGS Panel. Prevention of Falls in Older Persons. JAGS 2010;59:148-157.
2. Tinetti ME et al. Risk factors for falls among elderly persons living in the community. NEJM 1988;319:1701-7.
3. Podsiadlo D, Richardson S. The timed "Up & Go": a test of basic functional mobility. JAGS 1991;39:142-8.
4. Dargent-Molina P et al. Fall-related factors and risk of hip fracture. Lancet 1996;348:145-9.
5. Deandrea S et al. Risk factors for falls in community-dwelling older people: a systematic review and meta-analysis. Epidemiology 2010;21:658-68.
6. Briot K et al. Risk of falls in women treated with glucocorticoids. Joint Bone Spine 2009;76:637-43.
7. Leipzig RM et al. Drugs and falls in older people: a systematic review and meta-analysis. JAGS 1999;47:30-9 (Part I), 40-50 (Part II).
8. Cruz-Jentoft AJ et al. Sarcopenia: revised European consensus. Age Ageing 2019;48:16-31.
9. Lord SR et al. Multifocal versus single-lens glasses and falls. Optom Vis Sci 2002;79:S264.
10. Muir SW et al. Effect of a clinical decision tool on falls prevention. JAGS 2012;60:1471-8.
11. Clemson L et al. The development, implementation, and evaluation of a home fall prevention programme. Aust OT J 1997;44:S1-12.

## License
MIT — RheumaAI / Frutero Club / DeSci