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Table 4 Difference in motor outcomes associated with Mn exposure by community, Gauteng province, South Africa, 2016–2020

From: Severity of parkinsonism associated with environmental manganese exposure

  Mean difference between Mn smelter community vs. reference community in specified motor outcome (95 % CI)a
  Unadjusted Age-adjusted Fully-adjusted
UPDRS3, total scoreb 5.6 (4.1, 7.1) 6.6 (5.2, 7.9) 6.3 (4.9, 7.7)
UPDRS3 subscoresb
 Upper limb bradykinesiac 2.5 (1.8, 3.1) 2.9 (2.2, 3.5) 2.9 (2.2, 3.6)
Upper limb rigidityd 0.8 (0.5, 1.0) 0.8 (0.6, 1.1) 0.8 (0.5, 1.1)
 Lower limb bradykinesiad 0.5 (0.2, 0.7) 0.6 (0.4, 0.8) 0.6 (0.3, 0.8)
 Lower limb rigidityd 0.8 (0.6, 1.1) 0.9 (0.6, 1.2) 0.9 (0.6, 1.2)
 Rest tremore 0.1 (-0.01, 0.1) 0.1 (-0.005, 0.1) 0.04 (-0.02, 0.1)
 Action tremord 0.1 (0.01, 0.2) 0.1 (0.01, 0.2) 0.1 (-0.02, 0.2)
 Axial signsf 0.8 (0.3, 1.3) 1.1 (0.7, 1.6) 1.0 (0.5, 1.5)
Grooved pegboard, time (seconds)b
 Dominant hand -7.6 (-17.0, 1.9) 1.6 (-7.2, 10.5) 0.9 (-8.2, 10.0)
 Non-dominant hand -4.0 (-14.3, 6.3) 6.9 (-2.6, 16.3) 7.5 (-2.2, 17.1)
Kinematic testing, finger-tapping mean velocity (degrees/second)b
 Dominant hand -68.4 (-93.9, -43.0) -74.9 (-101.2, -48.7) -69.0 (-96.8, -41.3)
 Non-dominant hand -72.8 (-99.6, -46.1) -82.6 (-110.1, -55.2) -70.6 (-99.6, -41.6)
  1. Abbreviations: Mn manganese; UPDRS3 Unified Parkinson Disease Rating Scale motor subsection part 3
  2. a Based on 716 participants (621 in Meyerton and 95 in Ethembalethu). Age adjustment was using age as a continuous variable with natural cubic splines with five knots (5th, 27.5th, 50th, 72.5th, and 95th percentiles) as per Harrell’s placement method [35]. Fully adjusted means adjusted for age, sex, cigarette smoking (ever, former, current), and alcohol use (ever, former, current) (with all results confirmed in models with smoking as a dichotomous variable due to the small number of former smokers)
  3. b Poorer motor performance is indicated by greater UPDRS3 scores, greater grooved pegboard times, and lower finger-tapping velocities
  4. c Sum of six UPDRS3 subscores: Finger-tapping, hand rotations, and rapid arm movements for each limb
  5. d Sum of the two UPDRS3 subscores (one for each limb).
  6. e Sum of five UPDRS3 subscores: Upper limbs, lower limbs, and face
  7. f Sum of eight UPDRS3 subscores: Speech, facial expression, neck rigidity, difficulty arising from a chair, posture, gait, postural instability, and global bradykinesia