The puzzling incidence of testicular cancer in New Zealand: what can we learn?

BACKGROUND: Testicular germ cell tumour is the most common cancer to be diagnosed among young men. In New Zealand, we have observed some puzzling trends in the epidemiology of this disease. METHODS: We have conducted a narrative review of available evidence regarding the puzzling epidemiology of testicular germ cell tumour in New Zealand and discussed the possible drivers of these trends. RESULTS AND DISCUSSION: Whereas testicular cancer is most commonly a disease of White men, in New Zealand it is the indigenous Maori population that suffer by far the greatest rate of disease (age-adjusted relative risk: 1.80, 95% CI 1.58-2.05). Even more curiously, the rate of testicular germ cell tumour among Maori men aged 15-44 (28/100,000) is substantially greater than for Pacific Island men (9/100,000), a rare example of divergence between these two populations in terms of the incidence of any disease (cancer or otherwise). Our observations beg the following questions: first, why are rates of testicular germ cell tumour so much higher among Maori New Zealanders compared to the already high rates observed among European/Other New Zealanders? Second, why are rates of testicular germ cell tumour so completely divergent between Maori and Pacific New Zealanders, when these two groups typically move in parallel with respect to the incidence of given diseases? Finally, what might we learn about the factors that cause testicular germ cell tumour in general by answering these questions? CONCLUSION: This review examines the possible drivers of our observed disparity, discusses their feasibility, and highlights new work that is underway to further understand these drivers.

Estimating the risk of acute rheumatic fever in New Zealand by age, ethnicity and deprivation.

In New Zealand, efforts to control acute rheumatic fever (ARF) and its sequelae have focused on school-age children in the poorest socioeconomic areas; however, it is unclear whether this approach is optimal given the strong association with demographic risk factors other than deprivation, especially ethnicity. The aim of this study was to estimate the stratum-specific risk of ARF by key sociodemographic characteristics. We used hospitalization and disease notification data to identify new cases of ARF between 2010 and 2013, and used population count data from the 2013 New Zealand Census as our denominator. Poisson logistic regression methods were used to estimate stratum-specific risk of ARF development. The likelihood of ARF development varied considerably by age, ethnicity and deprivation strata: while risk was greatest in Maori and Pacific children aged 10-14 years residing in the most extreme deprivation, both of these ethnic groups experienced elevated risk across a wide age range and across deprivation levels. Interventions that target populations based on deprivation will include the highest-risk strata, but they will also (a) include groups with very low risk of ARF, such as non-Maori/non-Pacific children; and (b) exclude groups with moderate risk of ARF, such as Maori and Pacific individuals living outside high deprivation areas.

Ethnic patterns of hypospadias in New Zealand do not resemble those observed for cryptorchidism and testicular cancer: evidence of differential aetiology?

It has been proposed that hypospadias, cryptorchidism, poor semen quality and testicular cancer might share common prenatal causes. We have previously demonstrated similar ethnic patterns for the incidence of testicular cancer and cryptorchidism - a known risk factor for testicular cancer. If the underlying exposure(s) that cause hypospadias, cryptorchidism and testicular cancer are shared, then we would expect the incidence relationship between ethnic groups to follow the same pattern across all three conditions. We followed a birth cohort of 318 345 eligible male neonates born in New Zealand between 2000-2010, and linked routinely collected maternity records with inpatient hospitalization and mortality records through to 2011. We searched hospitalization records for diagnoses of hypospadias, and used mortality records for censoring. We used Poisson regression methods to compare the relative risk of hypospadias between ethnic groups, adjusting for perinatal risk factors and total person time. We observed that European/Other children had the highest risk of hypospadias, with Maori, Pacific and Asian boys having around 40% lower risk of disease compared with this group (adjusted relative risk [RR]: Maori 0.62, 95% CI 0.55-0.70; Pacific 0.62, 95% CI 0.53-0.72; Asian 0.57, 95% CI 0.47-0.69). This contrasts substantially with our previous observations for cryptorchidism and testicular cancer, where Maori males have the greatest risk. Our observations suggest that - at least in New Zealand - the exposures that drive the development of hypospadias may differ to those that that drive the development of cryptorchidism and/or testicular cancer.

Test-retest reliability of dynamic plantar loading and foot geometry measures in diabetics with peripheral neuropathy.

Pedobarography is commonly employed in patients with diabetic peripheral neuropathy (DPN). However there is no evidence regarding test-retest reliability of this technique in this population, and therefore it was the purpose of the current study to address this clear gap. Dynamic plantar loading and foot geometry data were collected during barefoot gait with the EMED platform (Novel GmbH, Germany) from 10 patients with DPN over two sessions, separated by 28 days. Intra-class Correlation Coefficients (ICCs) and Coefficients of Variation (CoVs) were calculated to determine test-retest reliability. For dynamic plantar loading, reliability differed by outcome measure and foot region, with ICCs of >0.8 and CoVs of <15% observed in most cases. For dynamic foot geometry, ICCs of >0.88 and CoVs of <3% were observed for hallux angle, arch index and coefficient of spreading, while sub-arch angle was less reliable (ICC 0.76, CoV 23%). Overall, the current study observed high levels of test-retest reliability which were generally commensurate with that previously reported in healthy populations.

The Maori foot exhibits differences in plantar loading and midfoot morphology to the Caucasian foot.

The question being addressed in the current study was whether the diabetic Maori foot was more or less prone to ulceration than the diabetic New Zealand Caucasian (NZC) foot. Harris mat and pedobarographic analyses were employed to assess static and dynamic foot morphology and plantar loading in 40 Maori and NZC diabetic and non-diabetic participants. Significantly higher peak pressures were exhibited by the diabetic Maori participants compared to their NZC peers at the central forefoot. Significantly higher static and dynamic arch index values and significantly higher sub-arch angle values were exhibited by the non-diabetic Maori participants compared to their NZC peers. The latter findings suggest that healthy Maori may have a predisposition towards having a flatter foot than healthy NZC, which may have footwear design implications.