The average age of onset of Dupuytren Disease of all patients was 47.7 (median = 49). Figure 5.2 shows the age of onset by age groups and could be interpreted that for men, Dupuytren Disease starts about 10 years earlier than for women (Ross 1999). But that is an artifact caused by the specific age grouping. According to our data, men develop this disease on an average at the age of 46 and women at an age of 50.1, i.e., only 4 years later (p < 0.001). Note that earlier onset for men appears even in the lowest age group, where work or lifestyle has no effect yet. Although in that age group statistical significance is low (male N = 21, 1.7 %; female N = 10, 1.2 %), it might still indicate genetic causes.

Family history is also affecting the age of onset. Figure 5.3 shows the data for all participants, excluding patients who were not sure.

On average our patients with confirmed family history report an onset of Dupuytren Disease at 44.9 years (median = 45), while those without family history have an average age of onset of 50.3 years (median = 51). For men with family history, we find 42.8 years and 49.4 years without (p < 0.001), for women 44.9 and 50.3 years, respectively (p = 0.003).

To explore the effect of drinking alcohol and smoking, patients were asked whether they were currently smoking or not (smoking: male = 11 %; female = 9 % with higher percentages in Europe and lower in the USA) and whether they were drinking less than 2 glasses of wine/pints of beer per day, more than 2 glasses or not drink at all. We did not inquire about previous habits (Table 5.1)

Figure 5.4a shows the effect of smoking on the age of onset for all patients. Figure 5.4b excludes other influences causing an earlier onset, like male gender or family history.

Smoking seems to cause an earlier onset. The effect is most obvious in the age group 30–39 (N = 50 smoking, 224 not smoking for all patients), where people already have smoked for a longer period of time. It seems to take a while until the effect builds up because it is still smaller in the age group 20–29. The effect is similar for both genders: in the age group 30–39 smokers develop Dupuytren Disease twice as often as nonsmokers: 32.4 % of male smokers vs. 16.1 % of male nonsmokers and 20.5 % of female smokers vs. 9 % of the female nonsmokers.

According to our results (Table 5.2; patients with age of onset < 15 are excluded), smoking men develop Dupuytren Disease 7 years earlier if they have no family history, and only 3 years earlier with family history, but unfortunately results for smokers are lacking statistical significance. You have to start with large numbers for such an analysis. Interestingly, for smoking + family history, the age of onset is about 9–10 years earlier for both, men and women.

Different to smoking we did not observe a negative effect of the drinking behavior on the onset of Dupuytren Disease (Table 5.3); p-values are varying between 0.12 and 0.77.

93 % of all respondents had Dupuytren Disease and 35 % had Ledderhose Disease. Of the patients with Dupuytren Disease, 30 % had Ledderhose Disease, 20 % Frozen Shoulder at least once (Germany alone, 8 %), 17 % knuckle pads, 12 % thyroid problems, and 5 % diabetes. 9.5 % of the male respondents had Peyronie disease. For the 4 most frequent comorbidities, knuckle pads seem to be related to an onset even earlier than Ledderhose Disease, while we find no effect of frozen shoulder or Peyronie disease on the age of onset of DD (Table 5.4). P-values were calculated by linear regression analysis using SPSS.

Patients were asked “Given your experience to date, how would you rank the medical community’s knowledge and experience with Dupuytren Disease?” on a range of 1–10 with 1 = no knowledge, 10 = knew everything. Figure 5.5 shows results by country. For better overview the ratings 1–3 (= bad; red), 4–7 (= medium; yellow), and 8–10 (= good; green) are combined.