Sibonga, Jean

NASA Technical Reports Server

Summary of Recommendations from Early Onset Osteoporosis 
Summit [Bone Summit] of June 2010: Occupational Risk 
Surveillance for Long-Duration Astronauts 
Office of Chief Health and Medical Officer [OCHMO] NASA HQ 
 March 23, 2011 
Modified Sept 26, 2011 for FE-
Task Group 
 SK/Sibonga/3-4556 
https://ntrs.nasa.gov/search.jsp?R=20110015966 2019-08-30T17:27:39+00:00Z
01,000
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In
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de
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10
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pe
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35-39                                   ≥ 85 
Age group (yr) 
Men Women Hip 
Spine 
Wrist 
35-39                                    ≥85 
 
Risk for Earlier Age-Related Fractures due to  Prolonged 
Spaceflight? 
Cooper and Melton, 1992 
Slide courtesy of Amin; adapted 
Microgravity Effects on the Human Body 
From Scientific American 
Scientific American 
Page No. 4  SMCCB-10-001  SK/Sibonga072910 
NUTRITIONAL BIOCHEMISTRY 
LABORATORY - JSC 
Following slides courtesy of  Dr. S M Smith 
Page No. 5  SMCCB-10-001  SK/Sibonga072910 
Calcium-regulating Hormones 
Nutrition SMO, unpublished data; Courtesy Dr. SM Smith 
  
Bone Turnover 
Slide Courtesy of Dr. SM Smith; Adapted by Sibonga 
Page No. 7  SMCCB-10-001  SK/Sibonga072910 
0 5 10 15 20 25
0
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5000
6000
7000
8000
9000
Low Na
High Na
Study Day
B
on
e 
B
re
ak
do
w
n
(C
TX
, µ
g/
d)
Heer, et al. 
Sodium/Bone 
Page No. 8  SMCCB-10-001  SK/Sibonga072910 
Nutrition and Bone 
Zwart, et al., JBMR, 2010 
Page No. 9  SMCCB-10-001  SK/Sibonga072910 
Issues for Panel to Consider 
 Current standards based upon DXA aBMD and World Health 
Organization [WHO] guidelines.  (for Operational and Long-term 
Clinical care.) 
 Astronauts are exposed to unique set of risk factors (established 
and possible) during space travel (e.g., weightlessness, endocrine 
perturbations, suboptimal nutrition, sarcopenia, radiation, 
hypobaric/hyperoxic EVAs, CO2). 
 Are we doing enough now  to address an  occupational health risk 
that may manifest later? 
 Can a “new line in the sand” to be drawn based upon QCT and FEM 
conducted in population studies?   
 
 Can this Task Group come up with  a set of bone parameters for 
new Bone medical standards? 
 
 
Page No. 10  SMCCB-10-001  SK/Sibonga072910 
Issues for panel to Consider. 2 
 Issues:    
• QCT is currently a research tool - no clinical guidelines developed at 
present time 
• Limited population data of QCT and fracture outcome 
• Not enough time to collect fracture-outcome data (astronaut and/or 
terrestrial) and meet schedules – a role for probabilistic risk 
assessments. 
• Exposure to ionizing radiation (1 hip QCT ~ 5 days ISS) 
 
 Collection of surveillance data from QCT and FEM to better inform 
current and future (longer missions?) decision-making 
 
 
Is DXA T-scorea above -
1? 
Accept into 
Corps Ineligible for Corps 
no 
possible 
no 
yes 
yes 
Is L1-1y DXA T-
score above -
1.5? 
No pre-flight 
intervention 
required 
Endocrine 
Evaluation for 
possible Tx. 
yes 
Is R1+0y DXA T-score 
above -2? 
Is R1+0.5y DXA T-score 
within 2% of preflight? 
Is R1+1.0y DXA T-score 
within 2% of preflight? 
Is R1+2y DXA T-score 
within 2% of preflight? 
Conduct R1+3y DXA 
yes 
no 
no 
no 
Conduct routine DXA every 
3 years from date of DXA 
indicating recovery within 
2%          of preflight   
Is R1+0y DXA T-score 
within 2% of preflight? 
no 
Does R1+2y QCT* 
indicate trabecular bone 
recovery and/or FE 
strength? 
+ 
yes 
yes 
yes 
yes 
yes 
R1+1y QCT*: FE strength 
and trabecular recovery 
R1+0y QCT*: FE strength 
and trabecular recovery 
Send to Dr. Petak 
no 
L1-(3-12) mo. QCT*: FE 
strength and trabecular 
recovery 
Is QCT derived FE 
strength  above (TBD)? 
Send to Dr. Petak 
no 
Flight 1 
CANDIDATE SELECTION 
TO ASTRONAUT CORPS 
PRE-FLIGHT 1 
POST-FLIGHT 1 
Is QCT-1y derived FE 
strength at time of 
recertification above (TBD)? 
yes no 
Certified for second 
flight  
Not certified for 
second flight 
no 
Is L2-1y DXA T-
score above -1.5? 
No pre-flight 
intervention 
required 
Consult Dr. Petak 
yes 
Proposed Use of QCT Technology for  
Clinical and Operational Decisions 
Flight 2 
PRE-FLIGHT 2 
POST-FLIGHT 2 
no 
•All designated QCT scans are for occupational surveillance purposes.   
•a: Total Hip, Femoral Neck, Trochanter 
Recommendations from an Expert Panel  
for Consideration by NASA 
watch & monitor 
watch & monitor 
Is R1+0y DXA T-score 
above -2? 
Is R1+0.5y DXA T-score 
within 2% of preflight? 
Is R1+1.0y DXA T-score 
within 2% of preflight? 
Is R1+2y DXA T-score 
within 2% of preflight? 
Conduct R1+3y DXA 
yes 
no 
no 
no 
Conduct routine DXA every 
3 years from date of DXA 
indicating recovery within 
2%          of preflight   
Is R1+0y DXA T-score 
within 2% of preflight? 
no 
Does R1+2y QCT* 
indicate trabecular bone 
recovery and/or FE 
strength ?  
+ 
yes 
yes 
yes 
yes 
yes 
R1+1y QCT*: FE strength 
and trabecular recovery 
R1+0y QCT*: FE strength 
and trabecular recovery 
Send to Dr. Petak 
no 
Send to Dr. Petak 
? + 
Additional clinical info ?  
watch & monitor 
watch & monitor 
no 
Page No. 12  SMCCB-10-001  SK/Sibonga072910 
The Long-duration Astronaut 
 Typical space mission duration – 163 ± 32d (range 90-
215d) 
 Average Age – 46.5 ± 4.5 y (range 36.8 – 55.3) 
 Male to Female Ratio – 3.8 : 1 
 Current total # per astronauts in corps – 34 of 331 
 # repeat fliers – 4  
 BMI – Male BMI 25.9 ± 2.2 (20.6 to 30.6); Female BMI 22.6 ± 
2.2 (20.4 to 25.4) 
 Wt and Ht- Males: Males:  81 ± 9 kg (62 to 101 kg), 177 ± 
6 cm (163 to 185 cm);                                      
 Females: 65 ± 7 kg (57 to 80 kg), 170 ± 4 cm (165 to 178 
cm) 
Page No. 13  SMCCB-10-001  SK/Sibonga072910 
BONE SUMMIT 
RECOMMENDATIONS 
June 2010 
Page No. 14  SMCCB-10-001  SK/Sibonga072910 
Use of Algorithm for Operational Decisions 
 Proposed: For flight certification (based upon Permissible Outcome Limit), if 
BMD data are ambiguous (BMD continuum), then individualized FE 
estimates of strength will better inform decision-makers regarding flight 
certification (using individualized estimates vs. relative risks). 
 FE before Flight 1 gives better estimation of low fracture risk (i.e., stronger 
bones) than DXA BMD and thus QCT/FE used for “GO” decision only not 
for “NO GO” decision 
 From Standards: “DXA scan values in the osteopenic range with a negative 
endocrine evaluation should not be considered disqualifying. These 
individuals should be closely monitored with appropriate imaging studies. 
Any associated underlying conditions or correctable causes of osteopenia 
should be treated. Long duration missions may result in significant bone 
loss. This should be considered when certifying astronauts with significant 
osteopenia for such missions.” 
 Proposed:  Apply FE bone strength threshold derived from population 
studies (TBD) to medical standards (consider as supplement to DXA) 
 
 
 
Page No. 15  SMCCB-10-001  SK/Sibonga072910 
Use of Research Data for Clinical Practice 
 Recommended Analysis -Bone strength estimated by Finite 
Element (FE) may provide the single best composite number 
because it integrates bone mineral density, elastic modulus, loading 
and structure (may not be 100% but better than status quo). 
 Recommended Use: FE bone strength estimates in conjunction with 
physical medicine and rehabilitation approaches in returning 
astronaut (Dr.  Sinaki consult) 
 Required Use  of QCT for Countermeasure Evaluation:  clinical 
trigger based upon trabecular bone compartment – not detectable by 
DXA but by QCT 
 Recommended Threshold: Apply FE bone strength as flight 
certification threshold but most pertinent for 2nd long duration flight 
(threshold based upon FE cut-points derived from population – and 
upon FE declines from first long duration flight – Space Med also 
provides input for acceptable declines ) 
 
Page No. 16  SMCCB-10-001  SK/Sibonga072910 
Rationale 
 “Although we are used to DXA measurements as clinical assessment of 
risk, the situation in the astronaut corps may be different.  Rather than think 
in population terms, it might be better to think in individual terms.”  (Panel 
member) 
 Spaceflight-induced changes to bones are not detectable by DXA (poor 
correlation) (see slide 28) 
 
 FE provides better assessment of bone strength following spaceflight. 
 
 Panel recognizes that fracture risk is LOW during an ISS mission although 
risk for stress fractures during flight exercise regimens may exist 
(opportunity for occupational surveillance data  to inform Bone Fracture 
Module of IMM). 
 
 If an astronaut has deficits in hip bone strength equivalent to the elderly (at 
L2- 1 year) (See slides 30-31), then re-exposing to long-duration space 
likely to increase the risk for early onset age-related fractures after return. 
 
Page No. 17  SMCCB-10-001  SK/Sibonga072910 
Summary Panel Recommendations 
 Recommend: QCT Technology for Occupational Risk 
Surveillance & Countermeasure validation   
 Four scans per one LD mission (per scan radiation < 5 
day ISS) 
• Preflight  30-45 days before Launch 
• Postflight by Return+22 days (or whenever return to US) 
• R+ 1 y 
• R+2 y 
 To monitor changes in hip structure and strength (not 
lumbar spine because of variability) 
• Describe spaceflight  effect (Risk for Fracture) 
• Monitor effect of peri-menopause prior to flight  
• Monitor recovery after return (Risk for Early Onset Osteoporosis) 
Page No. 18  SMCCB-10-001  SK/Sibonga072910 
Summary Panel Recommendations (cont) 
 To provide a clinical trigger* for medical response 
 To facilitate individualized estimations of bone strength,  
• To supplement DXA BMD measures when making 
clinical decisions, 
• To certify astronaut for long-duration flights by algorithm 
vs. Permissible Outcome Standard based upon 
projected BMD (1-2% loss/month) 
 
*Failure to recovery BMD in hip trabecular bone compartment by R+ 2 years.  
See endocrine evaluation by bone specialist for astronaut. 
 
Page No. 19  SMCCB-10-001  SK/Sibonga072910 
BACKGROUND DATA SLIDES 
T-scores not appropriate for monitoring 
spaceflight-induced changes or for predicting 
fractures in astronauts. 
Page No. 21  SMCCB-10-001  SK/Sibonga072910 
-25
-20
-15
-10
-5
0
5
10
0 300 600 900 1200 1500
Days-After-Landing
B
M
D
 C
ha
ng
e 
(%
)
Trochanter 
 
-25
-20
-15
-10
-5
0
5
10
0 300 600 900 1200 1500
Days-After-Landing
B
M
D
 C
ha
ng
e 
(%
)
Lumbar Spine 
Femoral neck 
DXA BMD increases in Postflight – is that recovery? 
Sibonga et al. BONE 41:973-978, 2007 




Research Study: QCT measures loss hip vBMD 
due to spaceflight in trabecular bone compartment 
(n=16 ISS) 
Index 
DXA 
 
%/Month 
Change + SD 
Index 
QCT 
%/Month 
Change + SD  
aBMD Lumbar 
Spine 
1.06+0.63* Integral vBMD 
Lumbar Spine 
 
0.9+0.5 
 
 
 
  Trabecular 
vBMD Lumbar 
Spine 
 
0.7+0.6 
aBMD Femoral 
Neck 
1.15+0.84* Integral vBMD 
Femoral Neck 
 
1.2+0.7 
  Trabecular 
vBMD 
Femoral 
 Neck 
 
2.7+1.9 
aBMD 
Trochanter 
1.56+0.99* Integral vBMD 
Trochanter 
 
1.5+0.9 
*p<0.01,  
n=16-18 
 Trabecular 
vBMD 
Trochanter 
2.2+0.9 
 LeBlanc, J Musculoskelet Neuronal Interact. 2000 ;  
Lang , J Bone Miner Res, 2004;  
Vico, The Lancet 2000 
Slide adapted from T. Lang., JBMR 2006. 
0.300
0.310
0.320
0.330
0.340
0.350
0.360
0.370
PRE POST 12MONTH
In
tg
. 
v
B
M
D
 (
g
/c
c
)
Visit
Femoral Neck
Bone Mineral Content  
(g) 
5.200
5.400
5.600
5.800
6.000
6.200
6.400
6.600
PRE POST 12MONTH
In
t.
 B
M
C
 (
g
)
Visit
Femoral Neck
* 
* 
P < 0.05 with respect to preflight*, postflight* 
Minimum 
Cross-sectional Area  
cm2 
      Pre    Post   12 
 Volumetric  
Bone Mineral Density  
g/cm3 
      Pre     Post      12      Pre    Post      12 
11.400
11.500
11.600
11.700
11.800
11.900
12.000
12.100
12.200
PRE POST 12MONTH
C
S
A
 (
c
m
2
)
Visit
Minimum CSA
 * ** 
** 
QCT Postflight – Changes in bone mass and structure  
at Femoral Neck 12 months after return 
-6.0%
-5.0%
-4.0%
-3.0%
-2.0%
-1.0%
0.0%
1.0%
-2.0% -1.5% -1.0% -0.5% 0.0%
C
ha
ng
e 
in
 F
E 
St
re
ng
th
Change in DXA Total Femur Areal BMD 
Stance
Fall
Stance: R2=0.23 
Fall: R2=0.05 
Astronaut Data:  Surrogates of bone strength do 
not correlate. Suggest that FE can pick up space-
induced changes in strength that DXA cannot. 
Slides courtesy of J Keyak; Bone. 2009 Mar;44(3):449-53. 

Results 
Stance Loading 
Max loss 
30% 
0 2 4  6 
Time (months) 
H
ip
 S
tre
ng
th
 (k
N
) 
16 
14 
12 
10 
  8 Mean post-
menopausal 
white women 
(SD=2 kN) 
Mean pre-
menopausal 
white women 
Results 
Fall Loading 
0 2 4  6 
Time (months) 
H
ip
 S
tre
ng
th
 (k
N
) 
4.0 
3.5 
3.0 
2.5 
 2.0 
1.5 
Max loss 
24% 
Mean post-
menopausal 
white women 
(SD=0.6 kN) 
Mean pre-
menopausal 
white women 
QCT:  Trabecular BMD at Femoral neck does not  
appear to show a recovery 2 to 4 years postflight 
 
QCT Extension Study (n=8) Postflight Trabecular BMD in hip.  Carpenter, D et al. Acta Astronautica, 2010. 


Summary of Recommendations from Early Onset Osteoporosis Summit. Summit [Bone Summit] of June 2010: Occupational Risk Surveillance for Long-Duration Astronauts

Summary of Recommendations from Early Onset Osteoporosis Summit. Summit [Bone Summit] of June 2010: Occupational Risk Surveillance for Long-Duration Astronauts

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