Secular growth and its harmful ramifications

How height is related to our health and longevity: a review

Most people believe that being taller and heavier is a sign of higher social status and privilege; however, an objective evaluation of the advantages and disadvantages of increased body size (excluding obesity) indicated that shorter, smaller bodies have numerous advantages in terms of health and longevity. With healthful nutrition and lifestyles, and good medical care, shorter people are less likely to suffer from age-related chronic diseases and more likely to reach advanced ages. A variety of biological factors explain the inherent benefits of smaller bodies. These include reduced cell replication, much lower DNA damage and reduced cancer incidence. Other beneficial factors include higher sex hormone binding globulin, higher insulin-like growth factor binding protein-1, lower insulin and lower insulin-like growth factor-1. We discuss recommendations for how taller people can minimize their risks. Future public health practices should focus on healthful nutrition, without promoting continued secular growth in height and weight.

Biodemography of exceptional longevity: early-life and mid-life predictors of human longevity

This study explores the effects of early-life and middle-life conditions on exceptional longevity using two matched case-control studies. The first study compares 198 validated centenarians born in the United States between 1890 and 1893 to their shorter-lived siblings. Family histories of centenarians were reconstructed and exceptional longevity validated using early U.S. censuses, the Social Security Administration Death Master File, state death indexes, online genealogies, and other supplementary data resources. Siblings born to young mothers (aged less than 25 years) had significantly higher chances of living to 100 compared to siblings born to older mothers (odds ratio = 2.03, 95% CI = 1.33-3.11, p = .001). Paternal age and birth order were not associated with exceptional longevity. The second study explores whether people living to 100 years and beyond differ in physical characteristics at a young age from their shorter-lived peers. A random representative sample of 240 men who were born in 1887 and survived to age 100 was selected from the U.S. Social Security Administration database and linked to U.S. World War I civil draft registration cards collected in 1917 when these men were 30 years old. These validated centenarians were then compared to randomly selected controls who were matched by calendar year of birth, race, and place of draft registration in 1917. Results showed a negative association between "stout" body build (being in the heaviest 15 percent of the population) and survival to age 100. Having the occupation of "farmer" and a large number of children (4 or more) at age 30 increased the chances of exceptional longevity. The results of both studies demonstrate that matched case-control design is a useful approach in exploring effects of early-life conditions and middle-life characteristics on exceptional longevity.

Growth hormone and aging: a challenging controversy

Although advanced age or symptoms of aging are not among approved indications for growth hormone (GH) therapy, recombinant human GH (rhGH) and various GH-related products are aggressively promoted as anti-aging therapies. Well-controlled studies of the effects of rhGH treatment in endocrinologically normal elderly subjects report some improvements in body composition and a number of undesirable side effects in sharp contrast to major benefits of GH therapy in patients with GH deficiency. Controversies surrounding the potential utility of GH in treatment of a geriatric patient are fueled by increasing evidence linking GH and cancer and by remarkably increased lifespan of GH-resistant and GH-deficient mice. Conservation of cellular signaling mechanisms that influence aging in organisms ranging from worms to mammals suggests that at least some of the results obtained in mutant mice are applicable to the human. We suggest that the normal, physiological functions of GH in promoting growth, sexual maturation and fecundity involve significant costs in terms of aging and life expectancy. Natural decline in GH levels during aging likely contributes to concomitant alterations in body composition and vigor but also may be offering important protection from cancer and other age-associated diseases.

A book of ideas collected from Medical Hypotheses: Death can be cured by Roger Dobson

A new collection of ideas from Medical Hypotheses by Roger Dobson is entitled Death can be cured and 99 other Medical Hypotheses. It consists of humorous summaries of Medical Hypotheses articles from the past 30 years. The book's humour derives mainly from the subject matter, although sometimes also from the 'unconventional' approach of the authors with respect to matters such as evidence, argument or inference. Medical Hypotheses has generated such a lot of apparently- or actually-bizarre ideas because it aims to be open to potentially revolutionary science. The journal's official stance is that more harm is done by a failure to publish one idea that might have been true, than by publishing a dozen ideas that turn out to be false. Bizarre ideas tend to catch attention, and may stimulate a valuable response--even when a paper is mostly-wrong. A paper may be flawed but still contain the germ of an idea that can be elaborated and developed. The journal review process is susceptible to both false positives and false negatives. False positives occur when we publish an idea that is wrong; false negatives occur when we fail to publish an important idea that is right, and a potential scientific breakthrough never happens. False positives are more obvious, since the paper will be ignored, refuted, or fail to be replicated--and often attracts criticism and controversy. Editors may therefore take the more cautious path of avoiding false positives more assiduously than false negatives; however, this policy progressively favours less-ambitious science. Consequently, in Medical Hypotheses the 'set point' of risk is nearer to the false positive end of the spectrum than for most journals - and the publication of many apparently-bizarre papers is a natural consequence of this policy.

Gender, socio-economic status and metabolic syndrome in middle-aged and old adults

Background

Studies that addressed social and economic determinants of cardiovascular diseases, consistently showed an increase prevalence of the individual features of metabolic syndrome in the lower socio-economic strata. Thus, this study aimed to evaluate the association between social class and metabolic syndrome in a sample of urban middle-aged and old Portuguese adults.

Methods

We evaluated 1962 subjects (1207 women and 755 men) aged 40 or more years. Marital status, education, occupation, menarche age and height distribution were used as socioeconomic indicators. Metabolic syndrome was defined according to the ATP III, by the presence of at least three of the following characteristics: waist circumference >102 cm in men and >88 cm in women; triglycerides ≥ 150 mg/dl; HDL cholesterol <40 mg/dl in men and <50 mg/dl in women; blood pressure ≥ 130/85 mm Hg; and fasting glucose ≥ 110 mg/dl. Proportions were compared using the chi square test or Fisher's exact test. Odds ratios (OR) and 95% confidence intervals (95% CI) were computed using unconditional logistic regression to estimate the magnitude of the associations.

Results

Metabolic syndrome was significantly more frequent in females (24.9 vs. 17.4, p < 0.001). In females, the odds favoring metabolic syndrome significantly increased with age and in unfavorable social class as described by occupation, and decreased with education level. In males, metabolic syndrome was significantly more frequent in the 60–69 years age class (OR = 1.82; 95%CI: 1.02–3.26) when compared to those in the 40–49 years age class. Concerning other socioeconomic indicators no significant associations were found.

Conclusion

This study showed that gender influenced the association of socio-economic status indicators with metabolic syndrome. Females in lower social classes, as defined by education and occupational classification, more frequently presented metabolic syndrome, no such association was found in males.

An alternative hypothesis to the obesity epidemic: Obesity is due to increased maternal body size, birth size, growth rate, and height

A new hypothesis for dealing with the obesity epidemic is based on changing several factors normally considered desirable by the medical community. These factors include reductions in pre-pregnancy maternal weight, modest reduction of infant birthweight, slower childhood and adolescent growth and reduced caloric intake from infancy through adulthood. The underlining roots for the obesity epidemic involve raised levels of insulin, insulin-like growth factor-1 and cell proliferation which are subject to human control. The implication of this hypothesis is that current measures are inadequate unless a much more comprehensive response is implemented to deal with the obesity epidemic.

Tying it all together: telomeres, sexual size dimorphism and the gender gap in life expectancy

The classic explanation that women outlive men solely due to hormonal and lifestyle differences, does not withstand a critical analysis. In developed countries, the average gap in life expectancy between the sexes is 7 years. It has widened over the last decades, despite the trend of women copying the 'unhealthy' lifestyle of men. Estrogen levels in postmenopausal women are virtually identical to estrogen levels in males and can hardly explain the discrepancy. Furthermore, testosterone got its bad reputation from one study on mentally retarded men, which has to be interpreted with caution. However, sexual size dimorphism with men being the larger sex in conjunction with the limited replication potential of human somatic cells might account for higher mortality rates in males, especially at old age. The hypothesis, as presented here, is based on the well-known concept of a cellular mitotic clock, which was discovered by Leonard Hayflick almost half a century ago. The underlying counting mechanism, namely the gradual erosion of chromosome ends (telomeres) due to the end replication problem of linear DNA molecules, was first described by Alexey Olovnikov in 1971 and with minor modifications has become a widely accepted paradigm. In a recent Lancet study, an inverse correlation between mean telomere length and mortality in people has been found. In this and two other studies, it was confirmed that males do have shorter telomeres than females at the same age. This is almost certainly a consequence of men being usually taller than women, although nobody has done an investigation yet. Clearly, a larger body requires more cell doublings, especially due to the ongoing regeneration of tissues over a lifetime. Accordingly, the replicative history of male cells might be longer than that of female cells, resulting in the exhaustion of the regeneration potential and the early onset of age-associated diseases predominantly in large-bodied males. Inherited telomere length variation between unrelated individuals might have obscured a clear correlation between body height and mortality, leading to conflicting results in some studies. Finally, I propose that the secular height increase over the last decades, of about 2.5 cm per generation in the western world, has to be blamed for the widening of the gender gap in life expectancy.

Is height related to longevity?

Over the last 100 years, studies have provided mixed results on the mortality and health of tall and short people. However, during the last 30 years, several researchers have found a negative correlation between greater height and longevity based on relatively homogeneous deceased population samples. Findings based on millions of deaths suggest that shorter, smaller bodies have lower death rates and fewer diet-related chronic diseases, especially past middle age. Shorter people also appear to have longer average lifespans. The authors suggest that the differences in longevity between the sexes is due to their height differences because men average about 8.0% taller than women and have a 7.9% lower life expectancy at birth. Animal experiments also show that smaller animals within the same species generally live longer. The relation between height and health has become more important in recent years because rapid developments in genetic engineering will offer parents the opportunity to increase the heights of their children in the near future. The authors contend that we should not be swept along into a new world of increasingly taller generations without careful consideration of the impact of a worldwide population of taller and heavier people.