A new study has found that older patients who test positive for the cytotoxin associated gene-A (CagA) strain of Helicobacter pylori may be more at risk of both osteoporosis and fractures.
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“Further studies will be required to replicate these findings in other cohorts and to better clarify the underlying pathogenetic mechanisms leading to increased bone fragility in subjects infected by CagA-positive H. pylori strains,” wrote Luigi Gennari, MD, PhD, of the University of Siena (Italy), and coauthors. The study was published in the Journal of Bone and Mineral Research.
To determine the effects of H. pylori on bone health and potential fracture risk, the researchers launched a population-based cohort study of 1,149 adults between the ages of 50 and 80 in Siena. The cohort comprised 174 males with an average (SD) age of 65.9 (plus or minus 6 years) and 975 females with an average age of 62.5 (plus or minus 6 years). All subjects were examined for H. pylori antibodies, and those who were infected were also examined for anti-CagA serum antibodies. As blood was sampled, bone mineral density (BMD) of the lumbar spine, femoral neck, total hip, and total body was measured via dual-energy x-ray absorptiometry.
In total, 53% of male participants and 49% of female participants tested positive for H. pylori, with CagA-positive strains found in 27% of males and 26% of females. No differences in infection rates were discovered in regard to socioeconomic status, age, weight, or height. Patients with normal BMD (45%), osteoporosis (51%), or osteopenia (49%) had similar prevalence of H. pylori infection, but CagA-positive strains were more frequently found in osteoporotic (30%) and osteopenic (26%) patients, compared to patients with normal BMD (21%, P < .01). CagA-positive female patients also had lower lumbar (0.950 g/cm2) and femoral (0.795 g/cm2) BMD, compared to CagA-negative (0.987 and 0.813 g/cm2) or H. pylori-negative women (0.997 and 0.821 g/cm2), respectively.
After an average follow-up period of 11.8 years, 199 nontraumatic fractures (72 vertebral and 127 nonvertebral) had occurred in 158 participants. Patients with CagA-positive strains of H. pylori had significantly increased risk of a clinical vertebral fracture (hazard ratio [HR], 5.27; 95% confidence interval, 2.23-12.63; P < .0001) or a nonvertebral incident fracture (HR, 2.09; 95% CI, 1.27-2.46; P < .01), compared to patients without H. pylori. After adjustment for age, sex, and body mass index, the risk among CagA-positive patients remained similarly significantly elevated for both vertebral (aHR, 4.78; 95% CI, 1.99-11.47; P < .0001) and nonvertebral fractures (aHR, 2.04; 95% CI, 1.22-3.41; P < .01).
The authors acknowledged their study’s limitations, including a cohort that was notably low in male participants, an inability to assess the effects of eradicating H. pylori on bone, and uncertainty as to which specific effects of H. pylori infection increase the risk of osteoporosis or fracture. Along those lines, they noted that an association between serum CagA antibody titer and gastric mucosal inflammation could lead to malabsorption of calcium, hypothesizing that antibody titer rather than antibody positivity “might be a more relevant marker for assessing the risk of bone fragility in patients affected by H. pylori infection.”
The study was supported in part by a grant from the Italian Association for Osteoporosis. The authors reported no potential conflicts of interest.
SOURCE: Gennari L et al. J Bone Miner Res. 2020 Aug 13. doi: 10.1002/jbmr.4162.