diff --git a/backend/calculations/scores.py b/backend/calculations/scores.py
index 108408b..076de8d 100644
--- a/backend/calculations/scores.py
+++ b/backend/calculations/scores.py
@@ -274,7 +274,7 @@ def calculate_health_stability_score(profile_id: str) -> Optional[int]:
 
         # 5. Regularity (10%) - sleep timing consistency
         if len(sleep_data) >= 7:
-            sleep_times = [s['total_sleep_min'] for s in sleep_data]
+            sleep_times = [s['duration_minutes'] for s in sleep_data]
             avg = sum(sleep_times) / len(sleep_times)
             variance = sum((x - avg) ** 2 for x in sleep_times) / len(sleep_times)
             std_dev = variance ** 0.5