A Cohort Study on Helicobacter pylori Serology ...

MILITARY MEDICINE, 166,5:411,2001

A Cohort Study on Helicobacter pylori Serology Before and After Induction in the Hellenic Navy Guarantor: Lt. Com. Ioannis Kyriazanos, MC, HN Contributors: ~t. .Com. Io~nis Kyriazanos, MC, HN*; Ioannis Ilias, MD DSct; Capt. Georgios Lazaris, MC, HN*;

Lt. Jr. Panagtotis Hountis, MC, HN*; Ass. Ens. Ioannis Deros, MC, HN*; Aggeliki Dafnopoulou, MD§; Capt. Konstantinos Datsakis MC, HNII

Background and Aims: To determine whether military personnel are at increased risk of Helicobacter pylori (HP) infection in proportion to their occupation during their national service in the armed forces. Materials and Methods: Serum samples were obtained from 142 young male Hellenic Navy recruits (mean age, 23.6 years; range, 20-30 years). The first specimen was obtained during their induction into the Hellenic Navy, and the second was obtained after having served for 8 months in different services within Greece. An enzyme-linked immunosorbent assay was used to detect HP-specific immunoglobulin Gantibodies. Statistical analysis was performed using the sign test, logistic regression, and the t test. Results: The crude seropositivity rate increased from 19.01% to 28.16% (p = 0.007). Of the 115 initially seronegative subjects, 17 (14.8%) seroconverted. The most important predictive variable for seroconversion was deployment in a crowded commission (>20 subjects) combined with the absence of air conditioning in personnel sleeping quarters (p = 0.03, odds ratio = 3.14). Conclusion: Our data suggest that the risk of HP infection increases among 20- to 30-year-old individuals during their national service. Degrading environmental conditions may play a major role in HP transmission between young adults who serve in the armed forces.

8-month tour of duty in the Hellenic Navy. Furthermore, we tried to identify possible risk factors that are implicated in the epidemiology of the infection during national service in this branch ofthe armedforces.

Materials and Methods Subjects The study population consisted of 142healthymale Hellenic Navy recruits (median age, 23.6 years; range, 20-30 years). All ofthe subjectswere Caucasian and camefrom different regions of the country. They were selected at randomfrom among 600 males inducted into the Hellenic Navy at the Naval Base of Salamis. The first blood samples were collected in January 1999, during their induction. The second samples were collected in September 1999, after 8 months ofpeacetime duty in various commissions in the Hellenic Navy. After centrifugation, serum samples were frozen at -70°C and thawed once before analysis.

Questionnaire During the second collection of blood samples, a questionIntroduction naire was completed for each subject. This questionnaire aselicobacter pylori (HP) infection is oneofthe mostcommon sessed the subject's commission (either in a vessel or land bacterial infections worldwide. Despite an immense body based) and the presence or absence of selected environmental of knowledge about HP, its mode of transmission is still un- factors (physical, biological, and socioeconomic). For the landclear. 1,2 Direct interpersonal or indirect (via a common source) based subjects, the physical factors concerned either their urtransmission could occurbyeitherthe oral-oral or the fecal-oral ban or rural placement (on or offnavalbases) and the presence route. Serology is an accurate method to screen for HP infec- ofair conditioning in their sleeping quarters. For personnel on tion." There is evidence for interfamilial and intrainstitutional navalvessels, the physical factors concerned the presence ofair clustering ofspecific strains ofHP. People living in overcrowded conditioning in the vessel's sleeping quarters.Thecrew personconditions and with limited sanitary facilities must be consid- nel were divided into groupsdepending on whether they served ered at high risk for HP infectlon." Regardless of these factors, on a newvessel (built less than 25 yearsbefore) or an oldvessel the majorrisk factor for HP infection seemsto be the socioeco- (more than 25 years since construction). For the estimation of nomic status ofan individual's family." More specifically, it has social factors, the subjects were classified as working in nonbeen shown that the HP infection status ofadults, regardless of crowded or crowded services (total personnel count < 20 subage, is linked to their socioeconomic status during youth and jects and > 20 subjects, respectively). Moreover, newgroups of not their current analogous situation. Thus, the aim of the subjectswere createdbydividing the totalairvolume ofsleeping present study was to evaluate the alteration in seropositivity quarters by the number of subjects (noncrowded service, air 10 m'': crowded service, airvolume/subject < rates in a large group of young Greek male recruits after an volume/subject> 10 m3) . We hypothesized that hygiene and living conditions on mili*Department ofSurgery, Naval Hospital ofSalamis, Salamis, Greece. tary installations were worse than those off military installatDepartment ofMedicine, Sotiria General Hospital, Athens, Greece. *Department ofImmunology, Naval Hospital ofAthens, Athens, Greece. tions. Thus, the personnel was divided into groups depending §Department ofRadiology, P.Faliron Medical Center, Athens, Greece. on the duration of their stay on the military installation (long [Oepartment ofGastroenterology, Naval Hospital ofAthens, Athens, Greece. stay, >10 days of 24 hours of continuous duty on military This manuscript was received for review inJanuary2000. The revised manuscript installations per month; short stay: 20 subjects

Yes n = 107 IgG+ n = 14

No n = 35 IgG+ n = 3

0.62 (p = 0.35)

Air volume/subject> 10 m 3

Yes n = 45 IgG+ n = 4

No n = 97 IgG+ n = 13

1.58 (p = 0.32)

24 hours of duty on a military installation/vessel > 10 days per month

Yes n = 66 IgG+ n = 4

No n = 76 IgG+ n = 14

3.50 (p = 0.02)

Air conditioning in sleeping quarters

Yes n = 68 IgG+ n = 5

No n = 74 IgG+ n = 12

2.44 (p = 0.08)

Personnel> 20 subjects combined with > 10 days per month of 24 hours of duty on a military installation

Yes n = 53 IgG+ n = 2

No n = 89 IgG+ n = 15

5.17 (p = 0.02)

Personnel < 20 subjects combined with air conditioning in sleeping quarters

Yes n = 100 IgG+ n = 8

No n = 42 IgG+ n = 9

3.14 (p = 0.03)

Air volume/subject < 10m3 combined with > 10 days per month of 24 hours of duty on a military installation

Yes n = 38 IgG+ n = 1

No n = 104 IgG+ n = 15

5.61 (p = 0.05)

Air volume / subject> 10m3 combined with air conditioning in sleeping quarters

Yes n = 88 IgG+ n = 12

No n = 54 IgG+ n = 5

0.65 (p = 0.31)

Serology Titers of HP immunoglobulin G (IgG) antibodies were determined at the Department of Immunology, Naval Hospital of Athens, using an enzyme-linked immunosorbent assay (HP IgG ELISA Kit, Hycor Biomedical GmbH, Kassel, Germany; interassay coefficient of variation, 7%; intraassay coefficient of variation' 4.30/0; sensitivity, 0.1 IU ImL). Levels of IgG were categorized as seropositive forHP according to an optical density titer ofIgG antibody to H. pylori ~ 0.5 Statistical Analysis Differences in seropositivity were evaluated withthe signtest. The correlation of all the data versus HP seropositivity was evaluated by logistic regression analysis. Theodds ratio (OR) of HP seropositivity was calculated with the t test from the SPSS statisticalpackage, version 8 (SPSS, Chicago, Illinois). Because ofthe smallnumber ofsubjects « 10), the t test was automatically converted to Fisher'stest by the SPSS statisticalpackage. Results Atthe induction ofthe subjectsin January 1999, 27 (19.01%) of 142 subjectswere seropositive for H. pylori. Of 115 subjects who were seronegative at induction, 17 (14.80/0) were found to Military Medicine, Vol. 166, May 2001

have had seroconverted at the second blood sampling in September 1999, afteran 8-month service period. Thecommission wasalways on Greek territory, and even forseafaring personnel, all of the missions were performed in Greek national waters. During their service, none ofthe subjectshad visited countries or places outside Greece where the risk of enteric infection is higher. The crude seropositivity rate increased from 19.01% at induction into the Hellenic Navy to 28.16% after 8 months of service. Differences in seropositivity rate were statistically significant (sign test, p = 0.007). The calculated annual seroconversion rate was 22.2%. In the evaluation ofpossible risk factors for the total number of subjects, logistic regression, with HP seroconversion as the dependent variable, showed that deployment in a crowded commission (>20 subjects) in combination with the absence of air conditioning in sleeping quarters was statistically associated with seroconversion (p = 0.03, OR = 3.14). Commission in a vessel or a land-based military installation, working in a crowded or noncrowded service, and the presence or absence of air conditioning in sleeping quarterswere not statistically associated with HP infection. On the contrary, serving 24 hours of continuous dutyona military installation formore than 10days per month was statistically associated with protection against HP infection (p = 0.02, OR = 3.50) and remained statistically

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413

H. pylori Serology in the Hellenic Navy

conversion rate was 22.2%, considerably higher than rates among young adults reported in studies from other developed countries." Theseresults representa majorincreasein the risk of infection during national service. This model of acquisition suggests that the pattern of acquisition of HP infection cannot be fully explained by a cohorteffect and that there is a continuous risk ofinfection in adults."Consequently, it is importantto determine which factors mayplaya role in the acquisition ofHP. Because several factors have been implicated, we tested the association of various possible risk factors to seroconversion. We assessed the total number of subjects and separated landbased personnel and seafaring personnel afteran 8-monthservice period in different services but always withinGreece. Race and sexwere not included as factors becauseall ofthe subjects were maleCaucasians. Factorsthat affect living conditions and sanitation by altering exposure to the bacterium (HP) are well documented as important determinants in the infectivity and transmissibility of HP.4.8 Although standards of hygiene were Discussion observed to be lower on vessels than on land-based installaArmed-forces personnel generally are assumed to be at in- tions,the subjects'commission (either ona vessel orlandbased) creasedrisk ofacquiring HP lnfection.t" In this study,wefound had no effect on HP prevalence. Forship crews, serving on a new that the prevalence of HP infection in Hellenic Navy soldiers or an oldvessel, a determinantthat is related directly to living increased from 19.01 % while living at home to 28.160/0 after an conditions and sanitation, did not reveal a statistically signifi8-month service period. This differentiation in seropositivity cant correlation with seroconversion. Consequently, although rate was statistically significant. The calculated annual sero- the prevalence of HP infection has been associated with low

significant even in combination with deployment in a crowded commission (p = 0.02, OR = 5.17). Results of serology versus the different risk factors for the total number of subjects are listedin Table I. Logistic regression analysis was performed separately for land-based personnel and crew personnel. Results are presentedinTables IIand III. Forthe land-based personnel, noneof the examined dichotomous variables correlated with HP IgG status. Onthe contrary, forthe subjectswho served on a vessel, the absence of air conditioning in the ship's sleeping quarters was statistically correlated with HP infection (p = 0.02, OR = 4.70). Again, serving 24-hourduties on military installations for more than 10 days per month was statistically associated with protection against HP infection (p = 0.02, OR = 5.69), even in combination with deployment in a crowded commission (>20 subjects, p = 0.02, OR = 5.69; air volume per subject < 10m", p = 0.03, OR = 7.41).

TABLE II RESULTSOF SEROLOGY VERSUS RISK FACTORS FOR HP INFECTION AMONG LAND-BASED PERSONNEL (N = 53) Variable

Group A

Group B

OR of A over B being HP IgG+

Deployment/commission

Inside Naval Base n = 24 IgG+ n = 4

Outside Naval Base n = 29 IgG+ n = 1

0.1 7 (p

=

0.11)

Personnel > 20

yes n = 24 IgG+ n = 2

no n = 29 IgG+ n = 3

1.14 (p

=

0.64)

Air volume/subject> 10 m 3

yes n = 26 IgG+ n = 1

no n = 27 IgG+ n = 4

4.35 (p

=

0.19)

24 hours of duty on a military installation > 10 days/month

yes n = 23 IgG+ n = 1

no n = 30

3.38 (p = 0.27)


yes n = 10 IgG+ n = 1

no n = 43 IgG+ n = 4

0.92 (p = 0.77)

Personnel> 20 subjects combined with > 10 days / month of 24 hours of duty inside military installation

yes n = 10 IgG+ n = 0

no n = 43 IgG+ n = 5

INF (p = 0.37)


yes n = 36 IgG+ n = 3

no n = 17 IgG+ n = 2

1.47 (p = 0.52)

Air volume/subject < 10 m'' combined with> 10 days/ month of 24 hours of duty inside military installation

yes n = 6 IgG+ n = 0

no n = 47 IgG+ n = 5

INF (p = 0.53)

Air volume/subject> 10 m" combined with air conditioning in sleeping quarters

yes n = 24 IgG+ n = 3

no n = 29 IgG+ n = 2

0.52 (p


=

0.41)

Military Medicine, Vol. 166, May2001


414 TABLEm

RESULTS OF SEROLOGY VERSUS RISK FACTORS FOR HP INFECTION AMONG SEAFARING PERSONNEL (N = 89)

Variable

Group B

Group A

OR of A over B being HP IgG+

Ship's construction year

Before 1975 n = 57 IgG+ n = 9

After 1975 n = 32 IgG+ n = 3

0.55 (p

Personnel > 20

yes n = 83 IgG+ n = 12

no n = 6 IgG+ n = 0

0.0 (p = 0.41)

Air volume/subject> 10 m"

yes n = 19 IgG+ n = 3

no n = 70 IgG+ n = 9

0.79 (p = 0.77)

24 hours of duty inside vessel> 10 days/month

yes n = 43 IgG+ n = 2

no n = 46 IgG+ n = 10

5.69 (p = 0.02)


yes n = 58 IgG+ n = 4

no n = 31 IgG+ n = 8

4.70 (p = 0.02)

Personnel> 20 subjects combined with > 10 days/ month of 24 hours of duty inside military installation

yes n = 43 IgG+ n = 2

no n = 46 IgG+ n = 10

5.69 (p = 0.02)


yes n = 64 IgG+ n = 5

no n = 25 IgG+ n = 7

4.59 (p = 0.02)

Air volume/subject < 10 m" combined with> 10 days/ month of 24 hours of duty inside military installation

yes n = 32 IgG+ n = 1

no n = 57 IgG+ n = 11

7.41 (p = 0.03)

Air volume/subject> 10 m" combined with air conditioning in sleeping quarters

yes n = 59 IgG+ n = 10

no n = 30 IgG+ n = 2

0.35

levels of hygiene and sanitation, 9,10 statistical evidence of this relationship has not been verified in the present study, a result that is in agreement with other studies.11 The importance of density of living, as a predisposing factor forthe transmissionofHP, has been suggested by several studIes," 10,12 and a highprevalence ofHPinfection has beenreported among persons living in institutions or on military installations.13, 14 In our study, the classification of subjects as serving in noncrowded or crowded services did not reveal any statistically significant correlation with seroconversion. We obtained analogous results when we created new subject groups by dividing the air volume ofthe sleeping quarters by the number of subjects living inside. Although wehypothesized that hygiene and living conditions on military installations were worse than those offmilitary installations, we found that staying more days per month on a military installation had a protective effect against HP infection. Theseresults couldbe attributed to consuming fast food offthe military installation. Preliminary results ofother questionnaires have indicated that the majority of subjects, when offmilitary installations, consume fast food products (datanot shown). The increased prevalence of infection with HP was associated with increased consumption of food from street vendors in other studies.16 Theprotective effect ofeatingon military installations was obvious in the assessment ofthe total number ofindividuals and the assessment of crew personnel. This variable reMilitary Medicine, Vol. 166, May 2001

=

0.31)

(p = 0.16)

mained protective even in combination with crowded service places (>20 subjects or < 10 m"ofair volume/subject) forboth groups ofsubjects. The role of environmental conditions in the transmission of HP infection has beenidentified in somestudies.16 In our study, the presence ofair conditioning in sleeping quarters proved the most statistically significant determinant of HP infection. This factor remained protective even in combination with crowded service places (>20 subjects or < 10 m" air volume/subject) for all subjects as well as for the seafaring group. In conclusion, we believe that the risk of HP infection increases among 20- to 30-year-old individuals during their national service in the Hellenic Navy, but the acquisition rate cannot be predicted solely on the basis ofa single variable. Our results did not indicate any strong relationship between the level of hygiene and HP infection. Thus, we suggest that the acquisition of HP is not facilitated specifically by low levels of sanitation and hygiene per se. These factors combined with degrading environmental conditions (crowding in sleeping quarters and the lackofair conditioning) playa major role in HP transmissionbetween young adultswho serve in the armed forces.

Acknowledgment The authors thank Ioanna Panagiotoy for her technical assistance in performing the serologic testing.



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