4 Discussion
In this study, we discovered a relationship between ED and osteoporosis
persisted after adjustment for potential confounding risk factors in
total male population. To the best of our knowledge, this is the first
large population-based cross-sectional study to investigate the
association of ED and osteoporosis for the all-aged (18-87 years) male
population. According to the results of this study, ED can be used as
significantly assessing factor for the prevalence of osteoporosis in
all-age adult male population. In addition, model with ED can
significantly improve the diagnosis ability for prevalence osteoporosis
in total population, which was further confirmed that the importance of
ED for diagnosis osteoporosis. Early intervention is of great importance
for osteoporosis, and the present findings might provide insights into
ED for the prevention and early detection of osteoporosis.
Many researchers concluded that a significant association between ED and
osteoporosis exists. In our study, ED was a significant risk factor
associated with osteoporosis. Concordant with an observational
cross-sectional study based on 119 recruited men with depressive, it is
reported that a low BMD was significantly associated with ED[20]. Similar
results were obtained in a population-based cohort study which included
4,696 elderly (60-74 years) Danish men, which revealed a higher risk of
osteoporotic fracture risk in men with self-reported ED[21]. However, a
study which included 76 men aged ≥50 demonstrated no association between
ED and osteoporosis, which was conducted from one region with a small
sample size (n=76), where the conclusion might not be completely
applicable to our study. Our study firstly based on all-aged (18-87
years) male population to explore the relationship between ED and
osteoporosis, and ED can be used as significantly assessing factor for
the prevalence of osteoporosis.
Some biological hypotheses have been proposed for the mechanism which
was responsible for the relationship between ED and osteoporosis.
Firstly, androgens levels were lower in patients with ED than without
ED, which plays an important role in the regulation of bone formation in
men [22,
23]. Secondly, patients with ED have
been highly associated with inflammation, and inflammatory cytokines may
inhibit osteoblast growth, thus causing osteoporosis[24]. Thirdly,
nitric oxide (NO) bioactivity is a possible pathogenic mechanism
underlying the relationship between ED and osteoporosis. NO is crucial
for penile engorgement and affect bone metabolism as well[25]. Fourth, the
condition of endothelial function is indicative of early stage of
atherosclerosis which is well established in both ED and osteoporosis,
which potentially explains the relationship between ED and osteoporosis[26]. Furthermore,
vitamin D which plays a major role in maintaining the bone health, has a
negative association with the risk of ED by promoting endothelial
dysfunction, which also might also play an important role in explaining
the association between ED and osteoporosis[27]. Finally,
traditional ED risk factors including diabetes mellitus, hypertension
and dyslipidemia are known to be predictors of osteoporosis. We suggest
that ED and osteoporosis share similar risk factors and a diagnosis of
ED increases the risk of osteoporosis. However, these co-morbidities do
not account for the complete relationship between ED and osteoporosis.
There were several limitations in this study which require
consideration. (1) No causal inference can be drawn due to the
cross-sectional design of the current study. Further prospective studies
are needed to illustrate the precise relationship between ED and
osteoporosis. (2) By including only Chinese subjects, the results of the
present study might not be representative of other ethnic groups,
especially those in developed or undeveloped countries. To some extent,
however, the present study of the Chinese population was still a
convenient sample and selection bias is inevitable. (3) Our assessment
of ED was performed using interviews and not confirmed by a specialist.
We are aware that conditions like ED are highly associated with social
stigmas. As a result of this, it is likely that ED was under-reported by
study participants. Furthermore, ED was evaluated only by asking ”the
ability to get and keep an erection for satisfactory intercourse?” and
the answers were categorical (no/yes) and International Index of
Erectile Function-5 items (IIEF-5) was not used in this study. However,
no IIEF-5 was used in some of studies and the self-reported with
categorical (yes/no) has strong correlations with IIEF-5[28-30]. (4) Data
on osteoporosis were obtained by ultrasound bone densitometer, as X-rays
were harmful to the health of participants and were not part of this
study. Ultrasound bone densitometer revealed a strong correlation
compared to X-rays[31] and has been
used mainly used to assess BMD in large epidemiology survey[32-34]. (5) No
androgen tests were performed in this study, and we could not identify
the prevalence of osteoporosis with the levels of androgen. However,
studies had confirmed that androgen deficiency is strongly associated
with ED [2,
35].