Influence of family size and birth order on risk of cancer: a population-based study

Number of Older Biological Siblings and Early-Onset Colorectal Cancer Risk

Colorectal cancer (CRC) is the third most common cancer in the United States.1 Although CRC incidence has declined in individuals >50 years, incidence is rising in adults <50 years (early onset).1 By 2027, CRC is projected to become the leading cause of cancer mortality in US adults <50 years.2 To combat the rising incidence of early onset CRC (EOCRC), national guidelines recently lowered the screening age from 50 to 45 years for average-risk individuals.3 Understanding the risk profile of EOCRC can help combat the rising burden in young adults, especially in those ineligible for screening.

Risk of prostate cancer in relatives of prostate cancer patients in Sweden: A nationwide cohort study

BACKGROUND

Evidence-based guidance for starting ages of screening for first-degree relatives (FDRs) of patients with prostate cancer (PCa) to prevent stage III/IV or fatal PCa is lacking in current PCa screening guidelines. We aimed to provide evidence for risk-adapted starting age of screening for relatives of patients with PCa.

METHODS AND FINDINGS

In this register-based nationwide cohort study, all men (aged 0 to 96 years at baseline) residing in Sweden who were born after 1931 along with their fathers were included. During the follow-up (1958 to 2015) of 6,343,727 men, 88,999 were diagnosed with stage III/IV PCa or died of PCa. The outcomes were defined as the diagnosis of stage III/IV PCa or death due to PCa, stratified by age at diagnosis. Using 10-year cumulative risk curves, we calculated risk-adapted starting ages of screening for men with different constellations of family history of PCa. The 10-year cumulative risk of stage III/IV or fatal PCa in men at age 50 in the general population (a common recommended starting age of screening) was 0.2%. Men with ≥2 FDRs diagnosed with PCa reached this screening level at age 41 (95% confidence interval (CI): 39 to 44), i.e., 9 years earlier, when the youngest one was diagnosed before age 60; at age 43 (41 to 47), i.e., 7 years earlier, when ≥2 FDRs were diagnosed after age 59, which was similar to that of men with 1 FDR diagnosed before age 60 (41 to 45); and at age 45 (44 to 46), when 1 FDR was diagnosed at age 60 to 69 and 47 (46 to 47), when 1 FDR was diagnosed after age 69. We also calculated risk-adapted starting ages for other benchmark screening ages, such as 45, 55, and 60 years, and compared our findings with those in the guidelines. Study limitations include the lack of genetic data, information on lifestyle, and external validation.

CONCLUSIONS

Our study provides practical information for risk-tailored starting ages of PCa screening based on nationwide cancer data with valid genealogical information. Our clinically relevant findings could be used for evidence-based personalized PCa screening guidance and supplement current PCa screening guidelines for relatives of patients with PCa.

Impact of maternal reproductive factors on cancer risks of offspring: A systematic review and meta-analysis of cohort studies

Background

A number of studies have reported on associations between reproductive factors, such as delivery methods, number of birth and breastfeeding, and incidence of cancer in children, but systematic reviews addressing this issue to date have important limitations, and no reviews have addressed the impact of reproductive factors on cancer over the full life course of offspring.

Methods

We performed a comprehensive search in MEDLINE, and Embase up to January 2020 and Web of Science up to 2018 July, including cohort studies reporting the association between maternal reproductive factors of age at birth, birth order, number of births, delivery methods, and breastfeeding duration and cancer in children. Teams of two reviewers independently extracted data and assessed risk of bias. We conducted random effects meta-analyses to estimate summary relative estimates, calculated absolute differences between those with and without risk factors, and used the GRADE approach to evaluate the certainty of evidence.

Results

For most exposures and most cancers, we found no suggestion of a causal relation. We found low to very low certainty evidence of the following very small possible impact: higher maternal age at birth with adult multiple myeloma and lifetime uterine cervix cancer incidence; lower maternal age at birth with childhood overall cancer mortality (RR = 1.15, 95% CI = 1.01–1.30; AR/10,000 = 1, 95% CI = 0 to 2), adult leukemia and lifetime uterine cervix cancer incidence; higher birth order with adult melanoma, cervix uteri, corpus uteri, thyroid cancer incidence, lifetime lung, corpus uteri, prostate, testis, sarcoma, thyroid cancer incidence; larger number of birth with childhood brain (RR = 1.27, 95% CI = 1.06–1.52; AR/10,000 = 1, 95% CI = 0 to 2), leukemia (RR = 2.11, 95% CI = 1.62–2.75; AR/10,000 = 9, 95% CI = 5 to 14), lymphoma (RR = 4.66, 95% CI = 1.40–15.57; AR/10,000 = 11, 95% CI = 1 to 44) incidence, adult stomach, corpus uteri cancer incidence and lung cancer mortality, lifetime stomach, lung, uterine cervix, uterine corpus, multiple myeloma, testis cancer incidence; Caesarean delivery with childhood kidney cancer incidence (RR = 1.25, 95% CI = 1.01–1.55; AR/10,000 = 0, 95% CI = 0 to 1); and breastfeeding with adult colorectal cancer incidence.

Conclusion

Very small impacts existed between a number of reproductive factors and cancer incidence and mortality in children and the certainty of evidence was low to very low primarily due to observational design.

Birth Order, Sibship Size, Childhood Environment and Immune-Related Disorders, and Risk of Lymphoma in Lymphoid Cancer Families

BACKGROUND

Familial aggregation of lymphoid cancers and immune-related disorders suggests a role for genetic susceptibility; however, few studies examine environmental factors. According to the hygiene hypothesis, adult-onset immune-related diseases may be a consequence of reduced childhood infectious exposures and aberrant immune development. In a cohort of 196 multiple-case lymphoid cancer families, we analyzed environmental factors related to the hygiene hypothesis.

METHODS

Family structure, childhood environment, and immune-related disorders were examined among 196 lymphoid cancer families, in relation to risk of lymphoid cancer. We report on 450 lymphoid cancer cases and 1,018 unaffected siblings using logistic regression models with generalized estimating equations to estimate ORs and 95% confidence intervals (CI) for association.

RESULTS

The risk of lymphoma tended to decrease with later birth order (OR = 0.83; 95% CI, 0.78-0.89) and larger sibship size (OR = 0.82; 95% CI, 0.79-0.85). High maternal education, above average family income during childhood, allergies (OR = 2.25; 95% CI, 1.44-3.51), and tonsillectomy (OR = 1.78; 95% CI, 1.14-2.78) were independent risk factors for lymphoma. Familial lymphoid cancer cases were more likely to report environment (OR = 1.90; 95% CI, 1.21-2.98) and drug (OR = 2.30; 95% CI, 1.41-3.73) allergies.

CONCLUSIONS

These associations underscore the complex etiology of familial lymphoma. To our knowledge, this is the largest multiple-case family-based study that supports the hygiene hypothesis contributing to lymphoid cancer risk.

IMPACT

Understanding the mechanism by which environmental and lifestyle factors affect lymphoid cancer risk may advance cancer prevention, even in the familial context.

Familial colorectal cancer risk in half siblings and siblings: nationwide cohort study

OBJECTIVE

To explore the risk of colorectal cancer in family members of patients with colorectal cancer, with an emphasis on subtypes of second degree relatives, especially half siblings, which were lacking in the literature.

DESIGN

Ambidirectional cohort study.

SETTING

Nationwide Swedish Family Cancer Data (record linkage).

PARTICIPANTS

All people residing in Sweden and born after 1931, with their biological parents, totalling >16 million individuals (follow-up: 1958-2015); of those with clear genealogy, 173 796 developed colorectal cancer.

MAIN OUTCOME MEASURES

Lifetime (0-79 years) cumulative risk and standardised incidence ratio of colorectal cancer among first degree relatives and second degree relatives.

RESULTS

The overall lifetime cumulative risk of colorectal cancer in siblings of patients was 7%, which represents a 1.7-fold (95% confidence interval 1.6 to 1.7; n=2089) increase over the risk in those without any family history of colorectal cancer. A similarly increased lifetime cumulative risk (6%) was found among half siblings (standardised incidence ratio 1.5, 95% confidence interval 1.3 to 1.8; n=140). The risk in people with colorectal cancer in both a parent and a half sibling (standardised incidence ratio 3.6, 2.4 to 5.0; n=32) was close to the risk in those with both an affected parent and an affected sibling (2.7, 2.4 to 3.0; n=396). Family history of colorectal cancer in only one second degree relative other than a half sibling (without any affected first degree relatives), such as a grandparent, uncle, or aunt, showed minor association with the risk of colorectal cancer.

CONCLUSION

Family history of colorectal cancer in half siblings is similarly associated with colorectal cancer risk to that in siblings. The increase in risk of colorectal cancer among people with one affected second degree relative was negligible, except for half siblings, but the risk was substantially increased for a combination of family history in one affected second degree relative and an affected first degree relative (or even another second degree relative). These evidence based findings provide novel information to help to identify people at high risk with a family history of colorectal cancer that can potentially be used for risk adapted screening.

Impact of changes in human reproduction on the incidence of endocrine-related diseases

The incidence rates of a wide range of diseases and conditions have increased over the last decades. There is controversy over the origin of these increases, whether they are caused by exposure to compounds thought to have an effect on the endocrine system, the "endocrine disruption theory", or whether some other factor is responsible. In this analysis, the authors take a closer look at the role that changes in reproductive factors have played in this respect. They apply the relative risks of age at first pregnancy and parity or family size to a set of Dutch demographic data from 1955 and 2015 and calculate the percentage of disease increase explained. The decrease in parity over the last decades explains an increase of 26% in testicular cancer. The combination of decrease in parity and increase in maternal age at first pregnancy explains an increase of 34% in hypospadias prevalence. This combination of decreased parity and increased maternal age at pregnancy explains an increase of 24% in childhood obesity prevalence. The authors further point to a perhaps even more profound effect of the trend toward smaller families. This trend has led to an estimated doubling of the proportion of children born from subfertile couples. Since children born from subfertile couples are more likely to be preterm or of low birth weight, the incidence of these conditions must have increased as well. Low birth weight and preterm delivery are risk factors for a wide range of diseases and conditions. The changes in human reproduction over the last decades have had a profound impact on the incidence of a range of diseases and conditions in the next generation and thus provide a sound explanation for a substantial portion of the reported increases. Key messages The incidence rates of a wide range of diseases and conditions have increased in the Western societies over the last decades. Many have argued that these increases are attributable to compounds thought to have effects on the human endocrine system: the endocrine disruption theory This analysis shows, however, that human reproductive factors such as maternal age at first pregnancy and parity explain substantial proportions of the reported increases.

Greater family size is associated with less cancer risk: an ecological analysis of 178 countries

BACKGROUND

Greater family size measured with total fertility rate (TFR) and with household size, may offer more life satisfaction to the family members. Positive psychological well-being has been postulated to decrease cancer initiation risk. This ecological study aims to examine the worldwide correlation between family size, used as the measure of positive psychological well-being, and total cancer incidence rates.

METHODS

Country specific estimates obtained from United Nations agencies on total cancer incidence rates (total, female and male rates in age range 0-49 years and all ages respectively), all ages site cancer incidence (bladder, breast, cervix uteri, colorectum, corpus uteri, lung, ovary and stomach), TFR, household size, life expectancy, urbanization, per capita GDP PPP and self-calculated Biological State Index (Ibs) were matched for data analysis. Pearson's, non-parametric Spearman's, partial correlations, independent T-test and multivariate regressions were conducted in SPSS.

RESULTS

Worldwide, TFR and household size were significantly and negatively correlated to all the cancer incidence variables. These correlations remained significant in partial correlation analysis when GDP, life expectancy, Ibs and urbanization were controlled for. TFR correlated to male cancer incidence rate (all ages) significantly stronger than it did to female cancer incidence rate (all ages) in both Pearson's and partial correlations. Multivariate stepwise regression analysis indicated that TFR and household size were consistently significant predictors of all cancer incidence variables.

CONCLUSIONS

Countries with greater family size have lower cancer risk in both females, and especially males. Our results seem to suggest that it may be worthwhile further examining correlations between family size and cancer risk in males and females through the cohort and case-control studies based on large samples.

Joint Families and Cancer Diagnosis in Rural India

Background: Each year, there are over a million new cases of cancer in India, which causes many untimely deaths and increases the economic burden to households. By focusing on preventative measures and finding socioeconomic and behavioral contributors to cancer, steps can be taken to help alleviate this burden. This study aims to find the effect living in a joint family can have on being diagnosed with cancer in rural India. Methods: The study estimates the effect living in a joint family, along with other demographic information, has on being diagnosed with cancer using a logit estimation model. The data for the study was collected from a survey was conducted on the households of the Handiganur village (N=251) comprising of several demographic, social, and medical questions. Results: The study found that living in a joint family lowers the odds of having cancer. The results indicate that living in a joint family reduces the probability of being diagnosed by 7.23 percentage points and is significant at a 5% level. Furthermore, among the other tested variables, eating habit is negatively significant at 5% level, suggesting that if a person eats 3 to 4 times a day his or her likelihood of suffering from cancer will be lowered by 6.55 percentage points. Access to public wells and drinking alcohol both increase the likelihood of being diagnosed with cancer by 7.90 (p<0.1) percentage points and 11.90 (p<0.05) percentage points respectively. Conclusions: The negative effect of joint family could be due to two possible reasons. The first is that there is in fact a biological reason. The second reason for this result could be a false negative, as it could be because people in joint families are not getting the necessary check-ups required to diagnose cancer.

Childhood brain tumours, early infections and immune stimulation: A pooled analysis of the ESCALE and ESTELLE case-control studies (SFCE, France)

BACKGROUND

Few studies have investigated whether early infections and factors potentially related to early immune stimulation might be involved in the aetiology of childhood brain tumours (CBT). In this study, we investigated the associations between CBT with early day-care attendance, history of early common infections, atopic conditions (asthma/wheezing, eczema, allergic rhinitis), early farm residence/visits and contact with animals.

METHODS

We pooled data from two nationwide French case-control studies, the ESCALE and ESTELLE studies. Children with a CBT diagnosed between 1 and 14 years of age were identified directly from the French National Registry of Childhood Cancers, while population controls were recruited from telephone subscribers. Odds-ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression adjusted for potential confounders.

RESULTS

The analyses included 469 cases and 2719 controls. We found no association between attending a day-care centre (OR: 0.9, 95%CI: 0.7-1.2) or having had repeated common infections (OR: 0.9, 95%CI: 0.7-1.2) in the first year of life and the risk of CBT. There was also no association with a history of asthma/wheezing (OR: 0.8, 95%CI: 0.56-1.1). Farm visits (OR: 0.6, 95%CI: 0.5-0.8) as well as contact with pets (OR: 0.8, 95%CI: 0.6-1.0) in the first year of life were inversely associated with CBT.

CONCLUSIONS

Our findings suggest a protective effect of early farm visits and contact with pets, but not with other markers of early immune stimulation. This might be related to immune stimulation but needs further investigation.

Childhood cancer incidence by ethnic group in England, 2001-2007: a descriptive epidemiological study

BACKGROUND

After the first year of life, cancers are the commonest cause of death in children. Incidence rates vary between ethnic groups, and recent advances in data linkage allow for a more accurate estimation of these variations. Identifying such differences may help identify potential risk or protective factors for certain childhood cancers. This study thus aims to ascertain whether such differences do indeed exist using nationwide data across seven years, as have previously been described in adult cancers.

METHODS

We obtained data for all cancer registrations for children (aged 0-14) in England from January 2001 to December 2007. Ethnicity (self-assigned) was established through record linkage to the Hospital Episodes Statistics database or cancer registry data. Cancers were classified morphologically according to the International Classification of Childhood Cancer into four groups - leukaemias; lymphomas; central nervous system; and other solid tumours. Age standardised incidence rates were estimated for each ethnic group, as well as incidence rate ratios comparing each individual ethnic group (Indian, Pakistani, Bangladeshi, Black African, Black Carribean, Chinese) to Whites, adjusting for sex, age and deprivation.

RESULTS

The majority of children in the study are UK born. Black children (RR = 1.18, 99% CI: 1.01-1.39), and amongst South Asians, Pakistani children (RR = 1.19, 99% CI: 1.02-1.39) appear to have an increased risk of all cancers. There is an increased risk of leukaemia in South Asians (RR = 1.31, 99% CI: 1.08-1.58), and of lymphoma in Black (RR = 1.72, 99% CI: 1.13-2.63) and South Asian children (RR = 1.51, 99% CI: 1.10-2.06). South Asians appear to have a decreased risk of CNS cancers (RR = 0.71, 99% CI: 0.54-0.95).

CONCLUSIONS

In the tradition of past migrant studies, such descriptive studies within ethnic minority groups permit a better understanding of disease incidence within the population, but also allow for the generation of hypotheses to begin to understand why such differences might exist. Though a major cause of mortality in this age group, childhood cancer remains a relatively rare disease; however, the methods used here have permitted the first nationwide estimation of childhood cancer by individual ethnic group.

Birth Order and Mortality: A Population-Based Cohort Study

This study uses Swedish population register data to investigate the relationship between birth order and mortality at ages 30 to 69 for Swedish cohorts born between 1938 and 1960, using a within-family comparison. The main analyses are conducted with discrete-time survival analysis using a within-family comparison, and the estimates are adjusted for age, mother’s age at the time of birth, and cohort. Focusing on sibships ranging in size from two to six, we find that mortality risk in adulthood increases with later birth order. The results show that the relative effect of birth order is greater among women than among men. This pattern is consistent for all the major causes of death but is particularly pronounced for mortality attributable to cancers of the respiratory system and to external causes. Further analyses in which we adjust for adult socioeconomic status and adult educational attainment suggest that social pathways only mediate the relationship between birth order and mortality risk in adulthood to a limited degree.

Season of birth and other perinatal risk factors for melanoma

BACKGROUND

Ultraviolet radiation (UVR) exposure is the main risk factor for cutaneous malignant melanoma (CMM), but its specific effect in infancy is unknown. We examined whether season of birth, a proxy for solar UVR exposure in the first few months of life, is associated with CMM in childhood through young adulthood.

METHODS

National cohort study of 3,571,574 persons born in Sweden in 1973-2008, followed up for CMM incidence through 2009 (maximum age 37 years) to examine season of birth and other perinatal factors.

RESULTS

There were 1595 CMM cases in 63.9 million person-years of follow-up. We found a sinusoidal pattern in CMM risk by season of birth (P=0.006), with peak risk corresponding to birthdates in spring (March-May). Adjusted odds ratios for CMM by season of birth were 1.21 [95% confidence interval (CI), 1.05-1.39; P=0.008] for spring, 1.07 (95% CI, 0.92-1.24; P=0.40) for summer and 1.12 (95% CI, 0.96-1.29; P=0.14) for winter, relative to fall. Spring birth was associated with superficial spreading subtype of CMM (P=0.02), whereas there was no seasonal association with nodular subtype (P=0.26). Other CMM risk factors included family history of CMM in a sibling (>6-fold) or parent (>3-fold), female gender, high fetal growth and high paternal education level.

CONCLUSIONS

In this large cohort study, persons born in spring had increased risk of CMM in childhood through young adulthood, suggesting that the first few months of life may be a critical period of UVR susceptibility. Sun avoidance in early infancy may play an important role in the prevention of CMM in high-risk populations.

Comparison of address-based sampling and random-digit dialing methods for recruiting young men as controls in a case-control study of testicular cancer susceptibility

Random-digit dialing (RDD) using landline telephone numbers is the historical gold standard for control recruitment in population-based epidemiologic research. However, increasing cell-phone usage and diminishing response rates suggest that the effectiveness of RDD in recruiting a random sample of the general population, particularly for younger target populations, is decreasing. In this study, we compared landline RDD with alternative methods of control recruitment, including RDD using cell-phone numbers and address-based sampling (ABS), to recruit primarily white men aged 18-55 years into a study of testicular cancer susceptibility conducted in the Philadelphia, Pennsylvania, metropolitan area between 2009 and 2012. With few exceptions, eligible and enrolled controls recruited by means of RDD and ABS were similar with regard to characteristics for which data were collected on the screening survey. While we find ABS to be a comparably effective method of recruiting young males compared with landline RDD, we acknowledge the potential impact that selection bias may have had on our results because of poor overall response rates, which ranged from 11.4% for landline RDD to 1.7% for ABS.

Assessing the social and physical determinants of circumpolar population health

INTRODUCTION

Systematic reviews of the social and physical determinants of health provide metrics for evaluation of programs to mitigate health disparities. Previous meta-analyses of the population health literature have identified several proximate social and physical determinants of population health in the circumpolar north including addiction, environmental exposures, diet/nutrition and global climate change. Proximate health determinants are most amenable to early detection and modification or mitigation through disease prevention or health promotion interventions.

DESIGN

There is a need for research to replicate these findings based on the latest science. This presentation describes a study applying Dahlgren and Whitehead's (1991) socio-ecological model of health determinants to identify the proximate social and physical determinants of health in the circumpolar north.

METHODS

The study consisted of a systematic review of recent studies that link determinants of health with the leading causes of mortality and morbidity in Alaska. Our search strategy employed a keyword search using the Circumpolar Health Bibliographic Database (CHBD) and 4 databases within the Web of Knowledge (WoK) data gateway. Keywords included various terms for the arctic, all relevant nations and territories within the region, as well as leading health outcomes.

RESULTS

Studies meeting the following inclusion criteria were reviewed: original research within a circumpolar population, published in English during 2011, and involving a rigorous demonstration of a link between a social determinant and selected health outcomes.

CONCLUSIONS

Study conclusions includes a list of determinants identified, their associated outcomes and the study designs implemented to assess that association.

Epidemiology, epigenetics and the 'Gloomy Prospect': embracing randomness in population health research and practice

Epidemiologists aim to identify modifiable causes of disease, this often being a prerequisite for the application of epidemiological findings in public health programmes, health service planning and clinical medicine. Despite successes in identifying causes, it is often claimed that there are missing additional causes for even reasonably well-understood conditions such as lung cancer and coronary heart disease. Several lines of evidence suggest that largely chance events, from the biographical down to the sub-cellular, contribute an important stochastic element to disease risk that is not epidemiologically tractable at the individual level. Epigenetic influences provide a fashionable contemporary explanation for such seemingly random processes. Chance events-such as a particular lifelong smoker living unharmed to 100 years-are averaged out at the group level. As a consequence population-level differences (for example, secular trends or differences between administrative areas) can be entirely explicable by causal factors that appear to account for only a small proportion of individual-level risk. In public health terms, a modifiable cause of the large majority of cases of a disease may have been identified, with a wild goose chase continuing in an attempt to discipline the random nature of the world with respect to which particular individuals will succumb. The quest for personalized medicine is a contemporary manifestation of this dream. An evolutionary explanation of why randomness exists in the development of organisms has long been articulated, in terms of offering a survival advantage in changing environments. Further, the basic notion that what is near-random at one level may be almost entirely predictable at a higher level is an emergent property of many systems, from particle physics to the social sciences. These considerations suggest that epidemiological approaches will remain fruitful as we enter the decade of the epigenome.