Risk factors for inguinal hernia in adult male Nigerians: A case control study
J.A. Ashindoitianga, N.A. Ibrahimb,*, O.O. Akinlolua
aDepartment of Surgery, General Hospital, Ikorodu, Lagos State, Nigeria
bDepartment of Surgery, Lagos State University College of Medicine and Teaching Hospital, Ikeja, Lagos State, Nigeria
a r t i c l e i n f o
Received 8 May 2012
Received in revised form
20 May 2012
Accepted 23 May 2012
Available online 4 June 2012
a b s t r a c t
Background: We sought to evaluate selected risk factors for development of inguinal hernia in adult male
Nigerians in a hospital based case control study. The aim was to identify the risks for this condition in our
population. This may assist in instituting appropriate preventive measures towards early detection and
Methods: All male patients aged 18 years and above who presented with primary inguinal hernia at the
General Surgical clinic of Ikorodu General Hospital between April 2009 and March 2011 were enrolled
into the study as cases. Control subjects were selected randomly from the general out-patient clinic.
Participants were interviewed during their first clinic attendance using a standardised questionnaire to
record their bio-data and the presence or absence of the risk factors. All study cases had hernia repair and
the type of hernia, whether indirect or direct was determined and documented. SPSS version 15.0 was
used in the statistical analysis and the risk factors among the cases and controls were compared using
univariate and multivariate logistic regression analysis.
Results: A total number of 404 male patients were interviewed. Two hundred and two were the cases
while the remaining 202 were the controls. Significant risk factors for inguinal hernia were positive
family history of inguinal hernia (p < 0.001 and strenuous work activities (p < 0.001).
Among the cases, 132 (65.3%) had indirect hernia while the remaining 70 (34.7%) had direct hernia.
Positive family history (p ¼ 0.011) and straining during urination or defecation (p ¼ 0.047) were the
factors significantly associated with the type of hernia.
Conclusion: Family history of inguinal hernia and strenuous work activity are the significant risk factors
for this condition in our setting. Public health initiatives targeting those at higher risk of hernia devel-
opment may help early detection and treatment; thereby reducing morbidity and mortality from this
? 2012 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.
Inguinal hernia is one of the most common surgical pathology. It
is the most common form of abdominal wall hernia and occurs
more frequently among adult men. Well over one quarter of adult
men in the united states of American would be expected to have
a medically recognized inguinal hernia.1The lifetime risk of
inguinal hernia repair is estimated to be 27% for men and 3% for
women.2The incidence and the prevalence of this condition in
Nigeria are not known. However, it is one of the most common
problems presentingto surgeons. In
a secondary level surgical practice in Nigeria, external hernia repair
constituted 56.1% of the surgical procedures undertaken.3In addi-
tion, significant proportion of patients with this disease present
a 14-yearreview of
late for treatment or with complications. Obstructed hernia
remains the most common cause of intestinal obstruction in
Certain factors have been implicated in the aetiology of primary
inguinal hernia.5They include the presence of a patent processus
vaginalis, failure of the shutter mechanism and altered metabolism
of collagen connective tissue and the extracellular matrix.6
Furthermore, Patient-related factors found to be associated with
inguinal hernia in adults include physical exertion and weight
lifting,7constipation,8straining during urination,9smoking,10
obesity,11ageing,1positive family history of hernia,12chronic
obstructive airway disease (COAD),12muscle deficiency following
previous appendectomy and abdominal surgery,13pelvic fractures
and trauma14and connective tissue disease.15
Despite the common occurrence and the clinical significance of
this condition, only few studies carried out largely among Cauca-
sians and Asians have investigated the risks for its development. To
the best of our knowledge, none has been done in an African
* Corresponding author.
E-mail address: firstname.lastname@example.org (N.A. Ibrahim).
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International Journal of Surgery 10 (2012) 364e367
population. We therefore evaluated some of the risk factors for
development of inguinal hernia in adult male Nigerians in
a hospital based case control study. The aim was to identify the
important risk factors for the disease in our population. This may
assist in instituting appropriate preventive measures targeted at
modifiable lifestyle and disease-related risk factors and early
detection of the condition by increasing awareness especially
among the groups at higher risk.
All male patients aged 18 years and above who presented with primary inguinal
hernia at the general surgical clinic of Ikorodu General Hospital between April 2009
and March 2011 were enrolled into the study as cases. The hospital is a secondary
level care centre serving largely the semi-urban and rural population Ikorodu local
Government area of Lagos state which has a population of about 0.5 million (2006
Control subjects were selected randomly from the general out-patient clinic.
They were patients with other conditions unrelated to hernia and are not predis-
posed to by any of the risk factors being assessed. Patients with history of hernia
repair were excluded from the control subjects. Cases and controls were age and sex
matched and informed consent was obtained before enrolment into the study.
Participants were interviewed during their first clinic attendance by the attending
physician among the authors using a standardised questionnaire.
Data recorded included age, body weight, height, body mass index (BMI),
smoking habit, presence or absence of chronic cough/COAD, constipation/straining
during defecation, straining during urination, history of inguinal hernia in a first
degree relation and obesity. Subjects with BMI >30 were considered obese. Type of
occupation and level of other regular physical activities were also documented and
thesewere used tocategorise participants into2 groups; those involved in strenuous
activities and those who were not. Level of physical activities was determined
employing the compendium of physical activities by Ainsworth et al.16as adapted by
Center for Disease Control and prevention (CDC) to categorize general physical
activities as defined by level of intensity. Activities classified as vigorous (metabolic
equivalent of task (MET) > 6.0) were considered strenuous while activities classified
as moderate (metabolic equivalent of task (MET) between 3.0 and 6.0) were
considered non-strenuous. All study cases had hernia repair and the type of hernia,
whether indirect or direct was determined and documented.
SPSS version15.0 was used in the statistical analysis. Risk factors were compared
between the cases and controls using univariate and multivariate logistic regression
analysis. Relative risks for cases compared with controls were estimated by calcu-
lating odds ratio (OR) with 95 percent confidence intervals (CI). Association between
the risk factors and the type of hernia was also determined by chi-square test.
P value of less than 0.05 was regarded as statistically significant.
A total number of 404 male patients were interviewed. Two
hundred and two who presented with inguinal hernia were the
cases while the remaining 202 were the controls. Age range for the
cases was from 16 to 80 years with mean age of 47.34 (SD ? 16.33).
The peak age range was 60e69 years. Age distribution of the cases
is as shown in Table 1. For the controls, their ages ranged from 17 to
83 and mean age was 45.48 (SD ? 16.85).
Distribution of the assessed risk factors for inguinal hernia
among the cases and the controls are as shown in Table 2. Signifi-
cant risk factors for inguinal hernia in this study were positive
family history of inguinal hernia (p ¼ 0.001) and strenuous work
activities (p ¼ 0.001).
Among the 202 subjects who presented with inguinal hernia,
132 (65.3%) had indirect hernia while the remaining 70 (34.7%) had
direct hernia. Age distribution and frequency of risk factors
according to the type of hernia is shown in Table 3. Positive family
history and straining during urination and defecation were the
factors significantly associated with the type of hernia in this study.
Higher percentage of direct hernia (41%) was observed in patients
who strain during urination or defecation (p ¼ 0.047) while three-
quarter among patients with positive family history of inguinal
hernia developed indirect hernia (p ¼ 0.011).
Inguinal hernia is predominantly a male disease and the inci-
dence increases with age. A national survey of general practices,
covering about 1% of the population of England and Wales in
1991e1992, found that about 95% of people presenting to primary-
care settings with inguinal hernia were males. It also found that the
incidence rose from about 11/10,000 person-years in men aged
16e24 years to about 200/10,000 person-years in men aged 75
years and over.17A third among patients in this study were aged 60
years and above, although, this age group constitutes only 5.5% of
the Nigerian male population. Increased age results in atrophy of
body muscles resulting in increased risk of hernia formation.
Positive family history of inguinal hernia is a significant risk
factor for inguinal hernia in this study. Forty-three percent among
patients in this study had family history of hernia in either the
parents or first degree relatives. In addition to being a significant
risk factor for development of inguinal hernia, positive family
history also predicts for recurrence of inguinal hernia following
repair.18Lau et al.12reported that family history of hernia was the
most important determinant factor for developing inguinal hernia
in adult males. In addition, a male subject who has a positive family
history of hernia is 8 times more likely to develop a primary
inguinal hernia. Genetic factors may play a role in the development
of hernia. Genes regulating collagen metabolism have been impli-
cated and studies on the biology of hernia formation suggest that
disturbance in collagen metabolism contribute to high recurrence
rates following hernia repair.15A decrease in ratio of type I/III
collagen is found in patients with inguinal, incisional and recurrent
inguinal hernias.15A recent study showed that level of matrix
metalloproteinases (MMPs) which are involved in the degradation
of collagen are higher in the fascia transversalis of patients with
inguinal hernia.19This may be responsible for weakness of the
fascia and development of hernia.
In this study, involvement in strenuous work activity is one of
the significant risk factors for inguinal hernia development. Studies
have shown that a person whose work activity involves lifting and
other strenuous work has higher risk of hernia formation.7,12In
addition to the type of weight lifted, the number of years in this
activitycontributes to the risk.7However, it is also reported that the
appearance of inguinal hernia may be attributed to a single stren-
uous event. Furthermore, indirect hernias are more likely to
present following such an event.20It is believed that strenuous
workactivities like liftingof heavy weight increase intra-abdominal
pressure causing breakage in the fibres of transversalis fascia. This
leads to weakness and results in the development of inguinal
hernia. It has been found that 20% of adults have a patent processus
vaginalis (PPV)21and this predisposes to development of inguinal
hernia in the presence of triggering factor such as raised intra-
abdominal pressure. In Nigeria, majority among the workforce
engage in farming and trading activities which involve carrying
heavy objects. Others, however, do not agree that occupation is
a factor in the development or aggravation of hernia. They hold the
belief that strenuous physical activity by itself does not cause
Age distribution of patients with inguinal hernia (N ¼ 202).
Age range (years)Number Percentage
Less than 20
80 and above
J.A. Ashindoitiang et al. / International Journal of Surgery 10 (2012) 364e367
primary or recurrent inguinal herniation. It is also reported that
there is seldom any subjective association between muscle strain
and the onset of groinhernia.22,23van Wessem et al.24reported that
the prevalence of PPV does not increase significantly with age and
concluded that the aetiology of indirect inguinal hernia in adults, as
in infants, is congenital. Studies conducted among Israelis and
Americans did not find significant association between physical
activities and inguinal hernia occurrence.1,9
Straining during defecation or urination causes increase in intra-
abdominal pressure and predisposes to inguinal hernia formation.
This factor did not significantly increase the risk of inguinal hernia
in our study population. This is similar to findings in a study among
Asian population.12Abramson et al.9found higher risk for inguinal
hernia in patients with features of benign prostatic hypertrophy
and not in those who had constipation. Ruhl et al.1also reported
that constipation or bowel movement frequency was notassociated
with higher risk of inguinal hernia. Chronic cough from COAD is
believed to be one of the causes of raised intra-abdominal pressure
and has been associated with increased risk of inguinal hernia.12
This was not a significant risk factor in this study. Our finding is
similar to the report from a survey in Israel.9
Obesity and overweight were not significant risk factors for
developing inguinal hernia in this study. Lower incidence of
inguinal hernia among overweight and obese men as compared
with normal-weight men was reported by Ruhl et al.1This finding
was supported by studies in Israel9and Netherlands.25It is sug-
gested that among heavier men, abdominal wall musculature may
be strengthened by the excess adipose tissue which provides
a stronger barrier against hernia formation. Our findings showed
that cigarette smoking was not a significant risk factor for inguinal
hernia. This is in support of reports from similar studies among
Chinese12and Americans.1Smoking is reported to have adverse
effect on connective tissue metabolism and has been proposed as
a risk factor for inguinal hernia development and reoccurrence.10
However, Jansen et al.18reported that smoking could be identi-
fied as an additional risk factor for early onset of hernia disease but
not for hernia recurrence.
Inguinal hernia remains a common disease among adult men.
Family history of inguinal hernia and strenuous work activity were
the significant risk factors for this condition in our setting.
Morbidity from inguinal hernia is still relatively high among our
population compared to what obtains in more affluent societies.
Many with the disease in our environment would not come for
treatment until complications arise.26Public health initiatives tar-
geting those at higher risk of hernia development may help early
detection and treatment;thereby reducing morbidityand mortality
from this condition.
Written informed consent was obtained and assurance of
confidentiality of responses was given to each respondent. Ethical
Distribution of risk factors for inguinal hernia among subjects and controls.
VariableControl n ¼ 202
Cases n ¼ 202
Univariate analysis Multivariate analysis
OR (CI ¼ 95%)
OR (CI ¼ 95%)
Straining during urination/defecation
Family history of inguinal hernia
86 (43) 5.138 (3.331e7.975)0.001 5.769 (3.548e9.380)0.001
177 (88) 1.099 (0.601e2.009)0.7591.286 (0.624e2.649)0.495
160 (79)1.566 (0.931e2.633)0.0911.808 (0.981e3.332)0.058
3 (1) 1 (0.5)
201 (99.5)199 (99)0.330 (0.034e3.200) 0.3390.208 (0.021e2.062)0.179
105 (52) 5.988 (3.667e9.777)0.001 7.018 (4.091e12.038)0.001
188 (93)0.642 (0.317e1.301)0.2190.442 (0.183e1.066)0.069
192 (95)0.904 (0.375e2.179) 0.8230.754 (0.261e2.173)0.601
Age distribution and frequency of risk factors according to the type of hernia
(n ¼ 202).
VariableType of hernia
Indirect (n ¼ 132)
Direct (n ¼ 70)
Family history of
8 (6)6 (9)
8 (6)2 (3)
J.A. Ashindoitiang et al. / International Journal of Surgery 10 (2012) 364e367
approval given by the relevant authorities of the hospital where the
study was carried out.
Funding for the research was by the authors.
JAA e study design, data collection, data analysis and write up of
NAI e study design, data analysis and final write up of
OOA e study design, data collection and write up of manuscript.
Conflict of interest
No conflict of interest to be declared.
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