The environmental and genetic determinants of cleft lip and palate in the global setting

Field: Medicine (Health Sciences)

In 2015, the Lancet commission published a report quantifying what Paul Farmer deemed the ?neglected stepchild of global public health??surgery. Although developed health systems have clearly established the necessity of surgery for a wide variety of health issues, disease maintenance, and patient quality of life, this subject has been essentially ignored in the otherwise passionate and multifaceted global health community. With an approximate 5 billion individuals lacking access to safe, affordable surgical care, simply providing care for all those in need is a distant and unlikely solution. Cleft lip and/ or palate is one of the most common birth defects (approximately 1 in 700 live births globally) and one of the many diseases that is inhibiting quality of life for patients who cannot receive surgical care. I propose to address this problem by first looking at the genetic and environmental determinants of cleft in low- and middle-income countries (LMICs), a birth defect that has traditionally only been addressed by surgery, but preliminary evidence suggests could be targeted for prevention. Second, I will work to understand the patient perspective through studying the barriers that patients face when trying to receive specialized surgical care in low-resource settings. ? The initial hypothesis I am pursuing is that smoke inhalation from cooking in the home over an open flame is a risk factor for cleft in combination with parental and household smoke exposure, which have been previously established in the literature. Smoke exposure from cooking occurs infrequently in developed countries but represents a high-proportion of smoke exposure in less-developed regions thus this exposure has been minimally studied with respect to cleft lip and palate development. The data is from a population-sampled case-control study of children with cleft lip and/or palate and healthy newborns from Vietnam, Philippines, Honduras, Nicaragua, Morocco, Congo, and Madagascar. Multivariable regression models were used to assess associations between maternal cooking during pregnancy, parental smoking, and household tobacco smoke with cleft. 2,137 cases and 2,014 controls recruited between 2012?2017 were included. While maternal smoking was uncommon (<1%), 58.3% case and 36.1% control mothers cooked over an open fire inside. Children whose mothers reported cook smoke exposure were 49% (CI:1.2?1.8) more likely to have a child with a cleft. This was consistent in five of seven countries. No significant associations were found for any other smoke exposure. Our finding of maternal cook smoke and cleft in low-resource countries, similar to maternal tobacco smoke in high-resource countries, may reflect a common etiology. This relationship was present across geographically diverse countries with variable socioeconomic statuses and access to care. Exposures specific to low-resource settings must be considered to develop public health strategies that address the populations at increased risk of living with cleft and inform the mechanisms leading to cleft development. ? To further understand this finding, I evaluated the hypothesis that the main effect that the first paper explored may miss susceptible genetic subpopulations of the cook-smoke and cleft association in Vietnam (where our findings showed the strongest effect). To test this, a genome-wide interaction scan (GWIS) using traditional GxE analyses, two-step methods, and statistically efficient one-step tests and genome-wide association study (GWAS) were conducted. Exposure was defined as exposure to smoke from cooking indoors over an open flame. 589 cases and 715 controls were available for analysis post QC measures (N= 1304). No SNPs reached genome-wide significance from the GWAS or GWIS analyses. No variants reached genome-wide significance, however 71 were of interest and reached a statistical threshold for exploration of p < 2E-6. Of the top 10 (excluding those grouped in the same gene/ region), 2 were identified from 3df test, 5 from the 2df, 1 from case-only and 2 from the traditional GxE test. No interesting hits were identified from the 2-step methods. Our top GWIS hits, rs1459270985 and rs1243867285, were identified by the unified model (3df test) and reside in the IQ motif containing H (IQCH), which is involved in testis development and spermatogenesis however a theoretical link to GxCookSmoke interaction and/ or NSOFC is unclear. One SNP identified via the case-only analysis, rs1254772630, is flanked by GRM8?a protein coding gene that has been linked to maternal plasma folate levels during pregnancy, which also plays a role in cleft development. The continued use of novel, statistically efficient methods to understand these relationships will be essential in the study of rare diseases, such as NSOFC, especially for individuals that reside in under-represented regions of the world and are at highest risk of living with disease. ? The first two hypotheses were explored using data from the International Family Study (IFS). IFS is an ongoing case-control study with supplemental parental trio data designed to examine genetic, environmental, lifestyle and sociodemographic risk factors for NSOFCs in eight LMICs (through August 2020). Interview and biological samples are collected for each family. The interview includes demographics, family history of cleft, diet and water sources, maternal pregnancy history, and other lifestyle and environmental factors. Seven of eight countries are currently summarized (2012?2017) for a total of 2,955 case and 2,774 control families with 11,946 unique biological samples from Vietnam, Philippines, Honduras, Madagascar, Morocco, DRC, and Nicaragua. IFS is the largest case set of NSOFCs with an associated biobank in LMICs currently assembled. The biobank, family, and case-control study now include samples from 8 LMICs where local health care infrastructure cannot address the surgical burden of cleft or investigate causal mechanisms. IFS can be a source of information and may collaborate with local public health institutions regarding education and interventions to potentially prevent NSOFC. ? Although prevention is undoubtedly the best long-term solution to decrease the burden of disease associated with cleft, there are believed to be upwards of five- million individuals currently living with cleft. The final portion of my dissertation will shed light on this issue using data collected with Operation Smile in five different countries assessing the patients structural, financial and cultural barriers to care. We conducted a cross-sectional study of children with cleft in Vietnam, Honduras, Madagascar, Mexico and Nicaragua between 2014 and 2018. An interview was conducted with the primary caregiver of each patient covering demographic, clinical, socioeconomic, geographic, and treatment characteristics. The Integrated Health Behavior Model (IBM) was used to conceptualize behavior. Descriptive statistics and confirmatory factor analysis were used to assess relationships between constructs and timeliness of care. A total of 901 patients and their families were surveyed from the five countries. Five latent constructs were included in the final framework: (personal agency- structure, personal agency- financial, perceived norm, environmental constraints, and knowledge and skills to perform the behavior). Of the patients seeking care for the first-time cleft phenotype, opinion of the family, perceived quality of available treatment, mother?s employment type, and father?s employment were all significantly related to reaching timely care before and after adjusting for country. This study maps the cultural, financial and structural barriers experienced by patients and their families to model care-seeking behavior across five diverse countries. As public health continues to increase investment into global surgery initiatives, it is necessary to understand these relationships and how they may differ by country to create effective and comprehensive programs that mitigate these barriers and enable patients to reach timely care.