Author(s): RISVANG, L.C., LILJEGREN, A.M.F.2, BAUMGART, J.K.3, VAN DIJK, J.W.4, STRØM, V.1,5, RAASTAD, T.1, JONVIK, K.L.1, Institution: NORWEGIAN SCHOOL OF SPORT SCIENCES, Country: NORWAY, Abstract-ID: 2104

INTRODUCTION:
Wheelchair (WC) users are at high risk of low bone mineral density (BMD) due to a lack of mechanical loading. Weight-bearing exercise can impact bone health, and thus, this study aimed to investigate the prevalence of low BMD in sports active versus non-sports active WC users and among different impairments.

METHODS:
In this cross-sectional study, BMD of lumbar spine, hip, and femoral neck were measured by dual-energy x-ray densitometry. Participants were defined as sports active if they were currently active in organized sports for >1 yr. WC users answered an adapted International Physical Activity Questionnaire (IPAQ-SF) for the week before testing. Data are presented as mean±SD or mean difference [CI]. One-way ANOVA, independent t-tests, and Pearson correlation analyses were employed. Only valid scans were included; analysis n is provided where data are missing.

RESULTS:
The study included 64 Norwegian WC users (35±10 yrs; 41% female; 50% sports active). Impairments were spinal cord injury (SCI; n=26), cerebral palsy (CP; n=21), spina bifida (n=7) or other (n=10). Overall, the BMD of the lumbar spine (n=62), hip (n=63), and femoral neck (n=63) was 1.10±0.22, 0.80±0.15 and 0.79±0.16 g/cm^2, respectively. The prevalence of osteopenia (Z-score<-1.0) was 45% for the lumbar spine, 69% for the hip, and 75% for the femoral neck.

Sports active had a lower prevalence of hip osteopenia than non-sports active (56% and 83%, n=32 vs. n=28; P=0.011). However, the BMD Z-scores did not significantly differ (0.4 [-0.1 – 1.0]; P=0.11). No differences were seen for lumbar spine or femoral neck BMD Z-scores. Lumbar spine BMD was weakly correlated with IPAQ-SF score (Pearson R=0.29; n=56; P=0.029). Lean body mass was moderately correlated with both lumbar spine and hip BMD (Pearson R=0.53 and R=0.43, respectively; n=60; both P<0.001), but no association was found for either current weekly strength training sessions or years of strength training experience with any of the BMD sites (all P>0.05).

Lumbar spine BMD Z-score was lower in those with congenital compared to acquired impairments (1.1 [0.4 – 1.9]; n=32 vs. n=29; P=0.004), in line with the tendency towards lower BMD Z-scores in those with CP compared to SCI (-1.2 [-2.4 – 0.0]; n=20 vs. n=24; P=0.050). However, hip BMD Z-score tended to be lower in those with acquired than congenital impairments (-0.5 [-1.1 – 0.0]; both n=31; P=0.056).

CONCLUSION:
Osteopenia was highly prevalent, varying from 45% at the lumbar spine to 75% at the femoral neck. Those with congenital impairments had lower BMD at the lumbar spine but higher BMD at the hip than those with acquired impairments. Sports active had a lower prevalence of hip osteopenia than non-sports active, although no differences were seen in Z-scores. Strength training is generally recommended to improve bone health but was not associated with BMD in our population. Thus, further investigations of the effects of sports participation and strength training are highly warranted.