Methodology and challenges for harmonization of nutritional data from seven historical studies.

BACKGROUND: Collection of detailed dietary data is labor intensive and expensive, harmonization of existing data sets has been proposed as an effective tool for research questions in which individual studies are underpowered. METHODS: In this paper, we describe the methodology used to retrospectively harmonize nutritional data from multiple sources, based on the individual participant data of all available studies, which collected nutritional data in Israel between 1963 and 2014. This collaboration was established in order to study the association of red and processed meat with colorectal cancer. Two types of nutritional questionnaires, the Food Frequency Questionnaires (FFQ) and the 24-h dietary recall (24HR recall), and different food composition tables, were used by the participating studies. The main exposure of interest included type of meat (total meat, red meat, and poultry) and level of processing. RESULTS: A total of 29,560 Israeli men and women were enrolled. In studies using FFQ,the weighted mean intakes of total, red, processed meat, and poultry were 95, 27, 37 and 58 gr/day and 92, 25, 10, and 66 gr/day in studies using 24HR recall, respectively.. Despite several methodological challenges, we successfully harmonized nutritional data from the different studies. CONCLUSIONS: This paper emphasizes the significance and feasibility of harmonization of previously collected nutritional data, offering an opportunity to examine associations between a range of dietary exposures and the outcome of interest, while minimizing costs and time in epidemiological studies.

Inequalities in end-stage renal disease: underprivileged and ethnic minority members are at higher risk.

BACKGROUND: Incidence of end-stage renal disease (ESRD) is higher in Israel than the European average. Socio-economic differences in ESRD have been reported globally, but many countries lack a national register. Using national data, we assessed which socio-demographic factors are associated with 5-year incidence of ESRD in Israel, where there is universal access to renal replacement therapy (RRT). METHODS: Data on all incident ESRD cases aged ≥20 years receiving chronic RRT between 1 January 2014 and 31 December 2018 (N = 7883) were collected from Israel's National Dialysis & Renal Transplant Register. Individual-level data on ESRD cases requiring RRT included residential area, age, gender, ethnicity (Jewish or Arab) and ESRD cause (diabetes, other, unknown/missing). Area-level data included age and sex distribution, socio-economic status (SES) and proportion of Arab population. The associations between individual-level socio-demographic characteristics and ESRD cause were tested in bivariate comparisons. The risk of developing ESRD during the study period (from all and specific causes) was estimated using multiple Poisson regression models with negative binomial distribution, using four parameters, namely sex, ethnicity, SES category and age strata, based on area-level distribution of these parameters, and with the whole population (aged ≥20 years) as the denominator. RESULTS: A socio-economic gradient was seen for ESRD from all causes, more marked for diabetic aetiology [rate ratio (RR)=0.45, 95% CI: 0.39-0.52 highest vs lowest SES categories] than from other (RR = 0.64, 95% CI: 0.55-0.75) or unknown cause (RR = 0.79, 95% CI: 0. 62-0.99). Based on population area-level data, predominantly Arab neighbourhoods showed higher risk for ESRD requiring RRT for all causes, with the strongest association for diabetes (RR = 1.69, 95% CI: 1.53-1.86) adjusted for SES, age and sex. CONCLUSIONS: A strong socio-economic gradient was demonstrated for ESRD requiring RRT. Arab ethnicity was associated with higher risk for ESRD, especially due to diabetes. Our findings suggest the need for allocation of health resources according to needs and culturally appropriate interventions for improving control of modifiable risk factors for chronic renal failure.