A study recently published in Scientific Reports investigated the potential associations between osteoporosis and age-related macular degeneration (AMD).
Give me some background.
Osteoporosis is a bone disease characterized by reduced bone mineral density (BMD) and alterations in the microarchitecture of bone tissue that can result in a higher prevalence of hip and vertebral fractures.
- Further: This condition is more prevalent among elderly postmenopausal women—and visual impairment due to age-related ocular diseases can increase the risk of falls and fractures in older adults.
Bring in AMD.
Early studies have suggested potential shared etiological factors between AMD and osteoporosis, such as:
- Systemic inflammation
- Metabolic disorders
- Oxidative stress
- Insufficient calcium intake
- Vitamin D deficiency
However: The relationship between osteoporosis and most age-related eye diseases remains poorly understood.
Now talk about the study.
In this cross-sectional study, investigators utilized data from the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2008 to evaluate the clinical characteristics of patients with AMD and osteoporosis.
The research team identified patients with both conditions as follows:
- AMD was determined by a standardized grading system based on the presence of key features of AMD on fundus photography
- BMD of the spine and femur was assessed via dual-energy X-ray absorptiometry (DXA)
In addition: Multivariate analyses were performed to account for confounding variables, such as:
- Age
- Gender
- Race
- Socioeconomic status
- Smoking habits
- Pre-existing health issues like diabetes or hypertension
Findings?
In total, 4,550 participants aged 40+ were included in this study, wherein the investigators found that osteoporosis was significantly associated with all types of AMD in women:
- Early and late AMD (odds ratio [OR]: 2.25, P < 0.001)
- Early AMD (OR: 2.05, P = 0.003)
- Late AMD (OR: 4.25, P = 0.022)
However: In men, the association between osteoporosis and AMD was not statistically significant for any type of AMD.
Anything else?
For women, the status of osteoporosis in the total femoral, femoral neck, femoral trochanter, and spine demonstrated a nonlinear relationship with AMD (P for nonlinear < 0.05).
- Moreover: For each unit increase in total femoral BMD, there was a reciprocal 0.08 decrease in total incidence of AMD in women, demonstrating a protective effect associated with higher bone density.
In subgroup analyses for race, Mexican American women had a strong positive association between osteoporosis and AMD (OR: 3.52) compared to non-Hispanic white individuals (OR: 1.86)
- Additionally: Individuals who had never smoked or consumed alcohol demonstrated lower OR values compared to their counterparts who currently or previously smoked or drank alcohol.
Expert opinion?
The study authors noted that, in females, estrogen plays a pivotal role in bone remodeling.
- “The influence of estrogen significantly enhances calcium absorption in the duodenum, which may explain the significant correlation between the decline in estrogen levels in postmenopausal women and the increased prevalence of osteoporosis,” they stated.
Further: Estrogen is “intricately linked” in the pathogenesis of AMD as it modulates several signaling pathways associated with AMD development.
What about anti-VEGFs and osteoporosis?
For patients with both AMD and osteoporosis, the influence of osteoporosis should be taken into account during the treatment of AMD.
- Why: Studies have shown that anti-vascular endothelial growth factor (VEGF) agents may be associated with a decrease in bone density in patients with osteoporosis.
Meaning: The study authors noted that changes in bone density and the progression of AMD in patients should be monitored regularly.
Any limitations?
These included:
- Due to the cross-sectional design, causal relationships between AMD and osteoporosis could not be established
- Due to limitations in the available data, investigators could not adjust for all potential covariates that may have influenced both osteoporosis and AMD
- They recommended that future studies incorporate various dietary patterns, lifestyle behaviors, the ingestion of vitamins and other nutrients, and the utilization of medications that might impact the progression of osteoporosis or AMD
- There are no additional refined metrics for osteoporosis, and relying exclusively on BMD may not have comprehensively mirrored the conditions of every patients
Take home.
These findings suggest a significant association between osteoporosis in women and an elevated risk of AMD.
“Investigating their associations could lead to the identification of novel pathogenic genes, signaling pathways, or biomarkers to provide new insights and directions for clarifying the mechanisms underlying AMD,” authors concluded.