Erectile dysfunction in Type 1 and Type 2 diabetics in Italy

Domenico Fedelea, Angela Bortolottib, Carlo Coscellic, Fausto Santeusaniod, Liliane Chatenoudb, Enrico Collie, Maurizio Lavezzarif, Marina Landonif, Fabio Parazzinib and on behalf of Gruppo Italiano Studio Deficit Erettile nei Diabetici,g

a Cattedra Malattie Metaboliche, Università di Padova, Padova, Italy.
b Istituto ‘Mario Negri’, Milano, Italy.
c Prima Divisione Medica, Ospedale di Parma, Parma, Italy.
d Cattedra di Endocrinologia, Università di Perugia, Perugia, Italy.
e Research and Development, Medical Department, Pharmacia & Upjohn, Kalamazoo, USA.
f Direzione Medica, Pharmacia & Upjohn Italia, Milano, Italy.

Reprint requests to: Fabio Parazzini, Istituto di Ricerche Farmacologiche ‘Mario Negri’, Via Eritrea, 62, 20157 Milano, Italy. E-mail: parazzini{at}irfmn.mnegri.it


    Abstract
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
Background Several studies reported data on the increased risk of erectile dysfunction (ED) in populations of diabetic men, but few presented data separately for Type 1 and Type 2 subjects. No comparison data for these diabetic subgroups are available with regard to risk factors for ED.

Methods Eligible for the study were men aged 20–69 years with a diagnosis of insulin-dependent (Type 1) or non-insulin-dependent (Type 2) diabetes who were observed on randomly selected days in 178 diabetes centres in Italy. Erectile dysfunction was defined as a failure to achieve and maintain an erection sufficient for satisfactory sexual performance.

Results The study population consisted of 1383 Type 1 and 8373 Type 2 men. The prevalence of ED increased with age for both groups. After taking into account the effect of age Type 2 men (37/100 men) tend to report ED less frequently than Type 1 men (51/100 men). A significant positive relationship was reported between ED and poor metabolic control and smoking for both Type 1 and Type 2 men, whereas high body mass index (BMI) increased only the risk of ED in Type 1 cases.

Conclusions The study offers a quantitative estimate of the prevalence of ED and its main risk factors in Type 1 and Type 2 diabetic subgroups.

Keywords Diabetes, erectile dysfunction, risk factors

Accepted 5 January 2000


    Introduction
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
Several studies have shown an increased risk of erectile dysfunction (ED) in diabetic men.1–14 Most information however refers to the total diabetic population and few studies have presented data separately for Type 110,15,16 and Type 2 men.10,17

Further, most studies comparing frequency of ED in Type 1 and Type 2 subjects include small population samples, often of different age, and only two studies10,16 reported data stratified for age. McCulloch et al.,10 in a study conducted in the UK, reported 35% ED for both Type 1 and Type 2. Brunner et al.15 reported 49% of ED in 59 Type 1 patients. Klein et al.,16 in a study including 359 Type 1 men aged less than 30 years at diagnosis and with diabetes lasting >=10 years, reported data stratified for age with 1% of ED at 21–30 years and 47% in patients >=43 years. Nathan et al.17 in a study of 125 Type 2 diabetic patients aged 55–74 years, reported a prevalence of 71% of ED.

Comparisons of risk factors for ED in diabetic subgroups are not available. This report describes the prevalence and determinants of self-reported ED in Type 1 and Type 2 men.


    Design and Methods
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
The general design of this study has been described.18 Briefly, eligible for the study were men aged 20–69 years with a diagnosis of insulin-dependent (Type 1) or non-insulin-dependent (Type 2) diabetes lasting for 1–30 years, attending, on randomly selected days, 178 diabetes centres in Italy during the period May–September 1996. Type 1 and Type 2 diabetic men were defined according to National Diabetes Data Groups indications19 (evaluation of C-peptide was not mandatory). We identified randomly the days, but all men consecutively attending the Centre on the selected days were eligible for the study.

A total of 9868 men entered the study. All were invited to a confidential interview carried out by medical staff of the centre during the visit when they were identified. Age, weight, height, marital status, cigarette smoking, weekly alcohol consumption, diabetic pathology and treatment, diabetes-related complications, selected medical history, and current medications were recorded. Whenever useful, information given by the patients was checked with the medical records.

Patients were also asked about their ability to achieve and maintain an erection sufficient for satisfactory sexual performance. If they answered that they were satisfied, the interview ended. If they were not satisfied, they were considered patients with ED. In this case, the men were further questioned about the severity of their sexual problems. Incomplete ED was defined when only some sexual performances were considered unsatisfactory, complete ED when all sexual performances were considered unsatisfactory. Interviews were carried out by a maximum of two trained interviewers per centre. The study protocol did not include any clinical or instrumental diagnostic procedures.

A patient was considered a smoker if he had smoked more than one cigarette/day for at least one year; an ex-smoker if he had smoked more than one cigarette/day for at least one year, but had stopped more than one year before the interview; a non-smoker if he had never smoked more than one cigarette/ day in his life.

Metabolic control was rated as follows: (1) good, glycosylated haemoglobin <7.5%; (2) fair, glycosylated haemoglobin 7.5–9%; (3) poor, glycosylated haemoglobin >9%. Metabolic control was rated according to the glycosylated haemoglobin value dating back no more than 3 months before the interview. An HPLC method20 was used in most centres for determination of glycosylated haemoglobin, with normal values 3.5–6%. Autonomic neuropathy was defined as presence of postural hypotension with faintness or syncope, anhidrosis, hypothermia, bladder atony, constipation, dry mouth and dry eyes from failure of salivary and lacrymal glands to secrete, blurring of vision from lack of pupillary and ciliary regulation.21

Confidence intervals (CI) of estimated frequency of ED were based on Poisson's approximation. Statistical differences in the frequency of ED among general, clinical or pharmacological subject characteristics were analysed using the usual {chi}2 test, comparing observed and expected events and, when appropriate, the test for trend. Odds ratios (OR) of ED adjusted for age and duration of diabetes were computed using unconditional multiple logistic regression, fitted by the method of maximum likelihood.22 Direct method was used to compute standardized rates, taking Type 2 subjects as reference population.


    Results
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
Of the men interviewed, 1383 (14%) were Type 1 and 8373 (86%) Type 2 (information on type of diabetes was missing in 112 cases). Twenty-six per cent of Type 1 and 37% of Type 2 reported ED. The frequency of ED increased with age for both groups, from respectively 13% and 16% of men with Type 1 and with Type 2 aged <45 years to 66% and 49% of those aged >=66 years (test for trend, P = 0.0001 for both). After taking into account the confounding role of age, men with Type 2 tended to report ED less frequently than men with Type 1 (age/duration of diabetes and standardized rate of ED 37% and 51%, respectively, Table 1Go).


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Table 1 Age distribution of Type 1 and Type 2 subjects
 
The association between ED risk and characteristics of diabetes is considered in Table 2Go. The OR of ED was higher in men with poorer metabolic control. In comparison with men with good metabolic control, the OR for ED were respectively for Type 1 and Type 2 1.5 and 1.7 in men with fair and 1.8 and 2.3 in men with poor control. For both groups, history of diabetes-related arterial, renal, or retinal diseases and neuropathy was associated with an increased risk of ED. The estimated OR tended to be higher, but not formally different, for Type 1 than for Type 2. The OR of ED increased with duration of diabetes both in Type 1 and Type 2. There was an increasing frequency of ED with increasing duration of diabetes for Type 2 subjects of all ages. Whereas a statistically significant association between duration of diabetes in Type 1 subjects and ED risk was observed only in men <=45 years (Table 3Go).


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Table 2 Distribution of Type 1 and Type 2 subjects according to the presence of erectile dysfunction (ED) and some characteristics of diabetes
 

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Table 3 Erectile dysfunction in (ED) relation to duration of diabetes in Type 1 and Type 2
 
The study subjects' general characteristics are considered in Table 4Go.


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Table 4 Distribution of Type 1 and Type 2 study subjects according to selected characteristics
 
In comparison with men with body mass index (BMI) < 24.3, the OR in Type 1 men with BMI 26.6–29.3 was 1.6 (95% CI : 1.1–2.4), and 2.5 (95% CI : 1.5–4.1) for those with BMI >29.3, with a significant trend (P = 0.0002). No association emerged between BMI and ED risk in Type 2 subjects.

Smoking was associated with an increased risk of ED in both Type 1 and Type 2. In comparison with never smokers, the risk was 1.6 (95% CI : 1.1–2.2) and 1.4 (95% CI : 1.3–1.6) for current smokers and 1.3 (95% CI : 1.0–1.9) and 1.4 (95% CI : 1.3–1.6) for ex-smokers, in Type 1 and Type 2 respectively. The risk increased with duration of the habit and the number of cigarettes smoked per day for both groups.

No significant association emerged between alcohol consumption and risk of ED in either group.

Some medical conditions such as anxiety, depression, cardiopathy, hypercholesterolaemia and hypertension were associated with an increased risk of ED in both the Type 1 and Type 2 groups, whereas arthritis, ictus/cerebral haemorrhage, pelvic/ medullary trauma and pelvic surgery or radiation increased the risk only in the Type 2 group. In particular the OR for ED were 2.0 (95% CI : 1.0–3.8) and 1.8 (95% CI : 1.3–2.3) for anxiety, 3.3 (95% CI : 1.5–7.5) and 1.3 (95% CI : 1.0–1.7) for depression, 2.9 (95% CI : 1.5–5.5) and 1.7 (95% CI : 1.5–2.0) for cardiopathy, 1.6 (95% CI : 0.9–2.8) and 1.3 (95% CI : 1.1–1.5) for hypercholesterolaemia, 1.4 (95% CI : 0.9–2.0) and 1.3 (95% CI : 1.2–1.4) for hypertension in Type 1 and Type 2 subjects respectively. Whereas only for Type 2 subjects the OR for ED was 2.0 (95% CI : 1.4–2.9) for arthritis, 2.1 (95% CI : 1.5–2.9) for ictus/cerebral haemorrhage, 2.0 (95% CI : 1.1–3.8) for pelvic/medullary trauma and 1.5 (95% CI : 1.2–2.0) for pelvic surgery or radiation (data not shown in Table).

Besides, ED was significantly more frequent in Type 1 and Type 2 diabetic subjects taking certain medications including tranquillizers, antihypertensives, cardiovascular treatments, diuretics and H2 antagonist. In particular the OR for ED were 2.6 (95% CI : 1.1–5.9) and 1.6 (95% CI : 1.2–2.2) for tranquillizers, 1.6 (95% CI : 1.1–2.4) and 1.2 (95% CI : 1.1–1.3) for antihypertensives, 3.8 (95% CI : 2.2–6.5) and 1.8 (95% CI : 1.6–2.1) for cardiovascular treatments, 3.2 (95% CI : 1.3–7.9) and 2.2 (95% CI : 1.7–2.8) for diuretics, 2.8 (95% CI : 1.1–6.7) and 1.3 (95% CI : 1.0–1.7) for H2 receptor antagonist, in Type 1 and Type 2 subjects respectively. Whereas only for Type 2 subjects the OR for ED was 1.9 (95% CI : 1.3–2.8) for antidepressants, 1.7 (1.1–2.6) for cancer drugs, 2.6 (95% CI : 1.4–4.6) for hormonal agents, 2.8 (95% CI : 1.1–7.3) for antipsychotics and 1.8 (95% CI :1.2–2.6) for urologics (Table 5Go).


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Table 5 Distribution of Type 1 and Type 2 diabetic subjects according to presence of erectile dysfunction (ED) and drug use
 
However, when we compared untreated and treated subjects with a specific medical condition, such as anxiety, hypertension, cardiopathy or hypercholesterolaemia no significant differences emerged in treated and untreated men (Table 6Go).


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Table 6 Distribution of Type 1 and Type 2 study subjects according to presence of erectile dysfunction (ED), medical history and drugs use
 

    Discussion
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
The study population consisted of 1383 Type 1 and 8373 Type 2 diabetic men self-referring for diabetes to a network of specialized centres. They cannot be representative of the Italian population of Type 1 and Type 2 men. Nevertheless, Italian diabetes centres take care of a large proportion of Italian diabetic men, about 50% of the estimated Italian population of diabetic men.23 A study conducted in Northern Italy has shown that diabetic men attending and not attending diabetic centres are largely similar in term of class and type of therapy.23 Further, the 178 centres participating in this study constitute 30% of such centres in Italy.24 Besides, the percentage of the two diabetic subgroups was comparable with that of the Italian diabetic population.25 However, it is possible that men affected by ED may attend diabetes centres more or less frequently so it is difficult to evaluate the direction and magnitude of this selection bias.

After taking into account the confounding role of age, the prevalence of self-reported ED was about 30% lower in Type 2 than Type 1 men. This contrasts with the figures from McCulloch et al.10 who reported no differences in prevalence between Type 1 and Type 2 groups. Compared to similar age groups, our prevalence data for Type 1 subjects were similar to that reported by Klein et al.16 (46% versus 47% of men aged >43 years with ED) but lower than that reported by Brunner et al.15 (26% versus 49%) and McCulloch et al.10 (22% versus 35% of men aged 20–59 years). Among Type 2 subjects we reported a lower prevalence than Nathan et al.17 (43% versus 71% for subjects aged >55 years), but similar values to McCulloch et al.10 (31% versus 35% for subjects aged 20–59 years) (Table 7Go).


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Table 7 Comparison of main results from epidemiological studies on prevalence of erectile dysfunction (ED) in Type 1 and Type 2 diabetic subjects versus our results
 
In line with previous findings,10,16 fair or poor metabolic control was associated with an increased risk of ED both in Type 1 and Type 2 subjects, underlining the possible benefit of glycaemic control in the prevention of ED.

In our study the frequency of ED was related to the duration of diabetes for both Type 1 and Type 2 subjects. In accordance with previous studies on the total diabetic population10,18 and on Type 1 diabetes,16 we found a significant relationship between the complications of diabetes (neuropathy, vascular diseases, retinopathy and nephropathy) and ED for both Type 1 and Type 2.

For Type 1, men with a high BMI were more likely to report ED than those with a lower BMI, as previously reported by Klein et al.16

For Type 2 the ED risk was similar in current smokers and ex-smokers, whereas in Type 1 men the risk was slightly higher in current smokers than ex-smokers. This contrasts with Klein's report.16 In that study Type 1 ex-smokers, but not current smokers, had an increased risk of ED.

As for total diabetic population, a greater risk for ED was reported both in Type 1 and Type 2 patients with some medical conditions, such as anxiety, depression, cardiopathy, hypercholesterolaemia or hypertension. Part of these associations may be explained by similar pathogenetic mechanisms, such as vascular damage. Erectile dysfunction was also reported to be more prevalent in Type 1 and Type 2 subjects taking certain groups of medications, including tranquillizers, antihypertensives, cardiovascular, diuretics and H2 receptor antagonists. Nevertheless, a drug-related effect on ED is difficult to distinguish from the effect of the disease and from concomitant exposure to other drugs. Therefore a much larger survey in a clinical population would be required to establish any aspect of medication effects on ED.

In conclusion, this study comparing prevalence data and risk factors for ED in Type 1 and Type 2 men showed that the risk of ED for both groups is influenced by age. A different prevalence of ED between the two diabetic subgroup subjects of the same age was also found. Further the results of the analysis highlight the role of some factors susceptible to intervention, such as metabolic control and smoking as potential determinants of the risk of ED for both Type 1 and Type 2.


    Appendix
 Top
 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
Gruppo Italiano Studio Deficit Erettile nei Diabetici

The following Clinicians are the participants of the group: Acqua Viva delle Fonti (N Antonacci); Alessandria (G Rosti, P Maresca, F Malvicino); Alghero (F Solinas, P Mereu); Amelia (G Cicioni); Ancona (F Mantero, GC Balercia); Ancona (I Testa, C Rasetti); Ancona (P Fumelli, M Boemi); Arenzano (M Comaschi, F Menozzi); Arezzo (L Ricci, T Vagheggi); Ascoli Piceno (D Zappasodi, G Mariani); Asola (S Baracchi); Assisi (A Frascarelli); Asti (V Ghia, L Gentile); Atri (P Di Berardino); Bari (GM Nardelli); Bassano del Grappa (G Amore); Bergamo (I Nosari, G Lepore); Biella (S Fontana, F Travaglino); Bologna (P Vannini, S Giangiulio); Bovolone (M Poli); Brindisi (A Trichera); Cagliari (L Carboni); Cagliari (M Manai, P Contini, F Farci); Cagliari (P Pintus, S Pintus); Cagliari (R Cirillo, E Cossu, S Cocco); Caltagirone (B Nativo); Caltanissetta (F Vancheri, G Gruttadauria, A Burgio); Campobasso (A Aiello, MR Cristofaro); Camposampiero (E Schirru, M Taniolo); Carbonia (L Vincis, G Melis); Carmagnola (C Marengo, M Comoglio); Casarano (R Monsellato); Castel di Sangro (J Grosso, V Di Tommasso); Castelfranco Veneto (G Beltramello, N Marin); Castellammare di Stabia (S Gentile); Castrovillari (F De Cunto); Catania (M Lunetta, C Sipione, G Mellini); Catania (V Borzì, P Banna); Catania (V Pezzino, F Purello, R Le Moli); Catanzaro (C Provenzano, L Puccio); Catanzaro (U Di Mario, G Leto); Cava dei Tirreni (M Agrusta); Cecina (S Schembri); Cesena (G Calbucci, C Dradi-Maraldi); Cetraro (L Mancuso, F De Berardinis); Chioggia (A Boscolo Bariga, G Ballarin); Città di Castello (C Campanelli); Cividale del Friuli (PM Miniussi, MA Pellegrini); Corigliano Calabro (A Staglianò); Correggio (D Orlandini, P Gaiti); Cosenza (D Branca, F Porto); Cremona (A Capellini); Crotone (B Cretella, D Voce); Cuorgnè (PD Bertello, L Gurioli); Desenzano (G Formentini); Dolo (G Drago); Empoli (V Vismara); Firenze (A Masotti, P Nannetti, S Carloni, D Venturi, G De Luca, P Turchi); Firenze (CM Rotella, G Bardini, SM Rizzello, F Cremasco); Firenze (U Bisacchi, E Mannucci); Fivizzano (C Pacetti, M Pellegrini); Foggia (A Parente, F Caldarella); Foligno (M Massi-Benedetti, AM Maremmani); Forlì (G Silvani, R Cigognani, C Valentini); Francavilla Fontana (A Muscogiuri); Gallarate (C Mazzi); Garbagnate (G Torchio); Gazzaniga (G Zibetti); Gemona (C Taboga); Genova (A Corsi, P Ghisoni); Genova (E Minuto, P Melga); Gissi (E D'Ugo); Giulianova (L Venturoni, S De Berardinis); Gualdo Tadino (A Coletti); Gubbio (A Angeli); Lanzo (S Beninati); Larino (M Tagliaferri); Latina (C Gnessi); Latisana (P Guidi); Legnago (F Marini, L Cogo); Lodi (G Cascone); Maniago (G Gaspardo); Mariano Comense (L Sciangula); Marsala (G Angileri, A Lo Presti); Massa (M Dolci, C Bongiorni, P Andreani); Matera (A Venezia); Messina (A Arcoraci, G Smedile); Messina (A Carducci, G Sobrio); Messina (D Cucinotta, A Di Benedetto, G Romano); Mestre (F Virgili, F Frigato, P Magnanini); Milano (G Testori); Milano (M Brivio, G Ballerio); Milano (M Lavezzari, F Pamparana); Modena (PG Benedetti, F Salerno); Modica (A Tribulato); Monfalcone (M Velussi); Montecchio Maggiore (F Calcaterra, F Cavaliere); Napoli (G De Matteo); Napoli (D Giuliano, R Marfella); Napoli (G Corigliano, G Ricci); Napoli (R Acampora, P Riccio); Napoli (S Mancini, F Saldalamacchia); Napoli (S Turco); Nocera Inferiore (A Salucci, U Amelia); Nuoro (G Pala); Oderzo (M Ferri); Oristano (F Mastinu, G Madau); Ortona (A Scarlatto, G Giambuzzi); Padova (D Fedele, G Bax, S Proto); Padova (S Del Prato, M Orrasch); Palermo (A Galluzzo, D Brancato); Palermo (E Savagnone, V Mangione, FC Raimondo); Palermo (S Biondo); Palermo (V Morici); Paola (D Saggio – L De Luca); Parma (A Strata, F Cioni); Parma (C Coscelli, F Saccardi, SM Tardio); Partinico (V Provenzano); Patti (G Arlotta, V Arlotta); Pavia (P Fratino, P De Cata, M Viggiano); Pavia (P Reboli); Penne (G Forestiero, E Antonacci); Perugia (F Santeusanio, A Baccarelli, P Bottini); Pesaro (A Spalluto, L Maggiulli); Pescara (F Capani, A Latorre); Pescia (F Galeone); Piacenza (D Giorgi Pierfranceschi, R Giorgi Pierfranceschi); Piedimonte Matese (A Pontieri); Pietra Ligure (C Ruffino); Pinerolo (R Sivieri); Pisa (R Navalesi, S Campi); Portogruaro (M Moretti); Potenza (V Sacco); Prato (A Arcangeli, C Crescenti, T Pedone); Ravenna (F Cannata, P Di Bartolo); Reggio Calabria (R Alessi, B Polimeni); Rho (A Bianchi); Rimini (M Parenti); Roma (G Ghirlanda, M Di Leo, A Marra, D Mauto); Roma (M Giuliano); Roma (G Menzinger, F Jacoangeli); Roma (C Teodonio, V Nicastro); Roma (G De Mattia, O Laurenti); Roma (G Marozzi, F Chiaramonte); Roma (G Testa); Romano di Lombardia (I Pellizzani); Rovigo (G Monesi, F Mollo, G Lisato); S Sepolcro (C Gasparri); Saluzzo (G Rizzi, GM Boffano, M Procopio); San Daniele del Friuli (MC Ariatta); Sassari (M Maioli, A Pacifico, P Fresu); Scandiano (V Miselli, A Zappavigna); Secondigliano (L Gesué); Siena (I Tanganelli, D Signorini); Siracusa (S Italia, S Leone); Sorrento (L Improta); Soverato (G Pipicelli); Spilimbergo (G Felace); Taranto (M Magno); Tempio (G Filigheddu); Teramo (E Lattanzi, D Di Michele, G Damiani); Terni (A Travaglini); Terni (S Gagliardo, P Narni); Torino (M Porta, GC D'Addona, P Passera); Torino (D Fonzo, M Veglio, M Deandrea); Torino (F Camanni, V Martina, M Tagliabue); Torino (GF Pagano, P Bodoni, S Marena); Torre Annunziata (G Di Somma Catello, G D'Alessandro); Trapani (G Allotta); Trento (P Acler); Treviglio (R Dodesini); Udine (C Noacco, F Colucci, L Tonutti); Urbino (M Vasta, M Sudano); Valdagno (R Gennaro); Vallo della Lucania (E De Vita); Varese (C Zandrini); Venaria (P Moiraghi, A Bogazzi); Venezia (G Bittolo Bon, C Zambon, E Moro); Vercelli (V Ferrari); Verona (M Muggero, L Gemma, L Bertolini); Viareggio (R Meniconi, A Bertoli, A Manfredi); Vibo Valentia (B Lacquaniti); Viterbo (U Corradini, M Ricchi).


    Acknowledgments
 
This study was partially supported by a grant of Pharmacia and Upjohn, Milan, Italy.


    Notes
 
g Appendix. Back


    References
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 Abstract
 Introduction
 Design and Methods
 Results
 Discussion
 Appendix
 References
 
1 Rubin A, Babbott D. Impotence and diabetes mellitus. JAMA 1958; 168:498–500.[ISI]

2 Schöffling K. Storungen der Keimdrusenfunktion bei mannlichen zuckerkraken. Beitr Sexualforsch 1960;19:1–83.

3 Montenero P, Donatone E. Diabètes et activité sexuelle chez l'homme. Diabete 1962;10:327–35.

4 Prikhozhan VM. Impotence in diabetes mellitus. Problemy Endokrinologii 1967;13:37–41.

5 Ellemberg M. Impotence in diabetes: the neurologic factor. Ann Intern Med 1971;75:213–19.[ISI][Medline]

6 Faerman I, Vilar O, Rivarola MA et al. Impotence and diabetes. Studies of androgenic function in diabetic impotent males. Diabetes 1972; 21:23–30.[ISI][Medline]

7 Kolodny RC, Kahn CB, Goldstein HH, Barnett DM. Sexual dysfunction in diabetic men. Diabetes 1973;23:306–09.[ISI][Medline]

8 Neubauer M, Schoffling K. Sexualstorungen bei diabetischen Mannern. In: Oberdisse K (ed.). Handbuch der inneren Medizin. 7/2B: Diabetes Mellitus. Berlin, Heidelberg, New York: Springer, 1977, pp.465–505.

9 Lester E, Grant AJ, Woodroffe FJ. Impotence in diabetic and non-diabetic hospital outpatients. Br Med J 1980;3:354–55.

10 McCulloch DK, Campbell IW, Wu FC, Prescott RJ, Clarke BF. The prevalence of diabetic impotence. Diabetologia 1980;18:279–83.[ISI][Medline]

11 Morley JE. Impotence. Am J Med 1986;80:897–905.[ISI][Medline]

12 Cavan DA, Barnett AH, Leatherdale BA. Diabetic impotence: risk factors in a clinic population. Diabetes Res 1987;5:145–48.[Medline]

13 Modebe O. Erectile failure among medical clinic patients. Afr J Med Med Sci 1990;19:259–64.[Medline]

14 Feldman HA, Goldstein I, Hatzichristou DG, Krane RJ, McKinlay JB. Impotence and its medical and psychosocial correlates: results of the Massachusetts male aging study. J Urol 1994;151:54–61.[ISI][Medline]

15 Brunner GA, Pieber ThR, Schattenberg S et al. Erektile dysfunktion bei patienten mit diabetes mellitus Type 1. Wien Med Wochenschr 1995;21:584–86.

16 Klein R, Klein BEK, Lee KE, Moss SE, Cruickshanks KJ. Prevalence of self-reported erectile dysfunction in people with long-term Type 1. Diabetes Care 1996;19:135–41.[Abstract]

17 Nathan DM, Singer DE, Godine JE, Perlmuter LC. Non-insulin-dependent diabetes in older patients. Am J Med 1986;81:837–42.[ISI][Medline]

18 Fedele D, Coscelli C, Santeusanio F et al. Erectile dysfunction in diabetics in Italy. Diabetes Care 1998;21:1973–77.[Abstract]

19 National Diabetes Data Group. Classification and diagnosis of diabetes mellitus and other categories of glucose intolerance. Diabetes 1979; 28:1039–57.[ISI][Medline]

20 Jaynes PK, Willis MC, Chan PP. Evaluation of minicolumn chromatographic procedure for the measurement of HbA1c. Clin Biochem 1985;18:32–36.[ISI][Medline]

21 Wilson JD et al. (eds). Principles of Internal Medicine 12th Edn. New York: McGraw-Hill, 1991, p.2105.

22 Baker NJ, Nelder JA. The GLIM System. Release 3. Oxford: Numerical Algorithms Group, Oxford, 1978.

23 Verlato G, Muggeo M, Bonora E, Corbellini M, Bressan F, De Marco R. Attending the diabetes center is associated with increased 5-year survival probability of diabetic patients. Diabetes Care 1996;19: 211–13.[Abstract]

24 Fedele D. Guida ai Centri Italiani per la Prevenzione e la Cura del Diabete. Roma: Edizioni ISIS, 1993.

25 Garancini MP, Calori G, Rutolo G et al. Prevalence of Type 2 and impaired glucose tolerance in Italy. An OGTT-based population study. Diabetologia 1995;38:306–09.[ISI][Medline]