So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

The purpose was to: 1) perform a systematic review of studies examining the relation between physical activity, fitness, and health in school-aged children and youth, and 2) make recommendations based on the findings. The systematic review was limited to 7 health indicators: high blood cholesterol, high blood pressure, the metabolic syndrome, obesity, low bone density, depression, and injuries. Literature searches were conducted using predefined keywords in 6 key databases. A total of 11,088 potential papers were identified. The abstracts and full-text articles of potentially relevant papers were screened to determine eligibility. Data was abstracted for 113 outcomes from the 86 eligible papers. The evidence was graded for each health outcome using established criteria based on the quantity and quality of studies and strength of effect. The volume, intensity, and type of physical activity were considered. Physical activity was associated with numerous health benefits. The dose-response relations observed in observational studies indicate that the more physical activity, the greater the health benefit. Results from experimental studies indicate that even modest amounts of physical activity can have health benefits in high-risk youngsters (e.g., obese). To achieve substantive health benefits, the physical activity should be of at least a moderate intensity. Vigorous intensity activities may provide even greater benefit. Aerobic-based activities had the greatest health benefit, other than for bone health, in which case high-impact weight bearing activities were required. The following recommendations were made: 1) Children and youth 5-17 years of age should accumulate an average of at least 60 minutes per day and up to several hours of at least moderate intensity physical activity. Some of the health benefits can be achieved through an average of 30 minutes per day. [Level 2, Grade A]. 2) More vigorous intensity activities should be incorporated or added when possible, including activities that strengthen muscle and bone [Level 3, Grade B]. 3) Aerobic activities should make up the majority of the physical activity. Muscle and bone strengthening activities should be incorporated on at least 3 days of the week [Level 2, Grade A].

/pdf/systematic-review-of-the-health-benefits-of-physical-4z2vkcynlg.pdf

Systematic review of the health benefits of physical activity and fitness in school-aged children and youth

The epidemiology of adult fractures is changing quickly. An analysis of 5953 fractures reviewed in a single orthopaedic trauma unit in 2000 showed that there are eight different fracture distribution curves into which all fractures can be placed. Only two fracture curves involve predominantly young patients; the other six show an increased incidence of fractures in older patients. It is popularly assumed that osteoporotic fractures are mainly seen in the thoracolumbar spine, proximal femur, proximal humerus and distal radius, but analysis of the data indicates that 14 different fractures should now be considered to be potentially osteoporotic. About 30% of fractures in men, 66% of fractures in women and 70% of inpatient fractures are potentially osteoporotic.

Epidemiology of adult fractures: A review

Many studies have shown cross-sectional (and two small studies, longitudinal) declines in total and/or free testosterone (T) levels, with age, in men. The extent to which decline in T is the result of the aging process per se, as opposed to chronic illness, medication use, and other age-related factors, remains controversial. The frequency with which aging leads to T levels consistent with hypogonadism has also not been defined. These issues bear on the potential use of T replacement in aging men, because aging and hypogonadism have, in common, reduced bone and lean body mass and muscle strength and increased total and abdominal fat. We measured T and sex hormone-binding globulin (SHBG), by RIA, in stored samples from 890 men in the Baltimore Longitudinal Study on Aging. Using a mixed-effects model, we found independent effects of age and date of sampling to reduce T levels. After compensating for date effects, which investigation suggested was artifactual, we observed significant, independent, age-invariant, longitudinal effects of age on both T and free T index (free T index = T/SHBG), with an average change of -0.124 nmol/L.yr and -0.0049 nmol T/nmol SHBG.yr. T, but not free T index, also decreased with increasing body mass index. Use of beta-blocking drugs was associated with higher T and higher free T index levels. Using total T criteria, incidence of hypogonadal T levels increased to about 20% of men over 60, 30% over 70 and 50% over 80 yr of age, and even greater percentages when free T index criteria were employed. Our observations of health factor independent, age-related longitudinal decreases in T and free T, resulting in a high frequency of hypogonadal values, suggest that further investigation of T replacement in aged men, perhaps targeted to those with the lowest serum T concentrations, are justified.

/pdf/longitudinal-effects-of-aging-on-serum-total-and-free-3ge3qog98w.pdf

Longitudinal Effects of Aging on Serum Total and Free Testosterone Levels in Healthy Men

https://www.archives-pmr.org/article/S0003-9993(01)63215-5/pdf

Gait variability and fall risk in community-living older adults: A 1-year prospective study

Epidemiology of hip fractures

We sought to determine current trends in the number of fall-related and osteoporosis-related proximal humeral fractures in elderly Finns during last three decades. We collected data from the National Hospital Discharge Register on all patients 60 years or older who were admitted to Finnish hospitals from 1970 to 2002 for primary treatment of proximal humeral fractures. Fractures induced by traffic accidents or other high-energy traumas were excluded. The number and incidence (per 100,000 patients) of fractures increased from 208 (number) and 32 (incidence) in 1970 to 1120 (number) and 105 (incidence) in 2002. The age adjusted incidence of proximal humeral fractures also showed an increase, from 51 (1970) to 129 (2002) in women, and from 14 (1970) to 48 (2002) in men. In women 80 years or older, the age specific incidence of fracture increased from 90 (1970) to 294 (2002), while in the other age groups trend changes were less extensive. The mean patient age also increased, from 73 years (1970) to 78 years (2002) in women and from 70 years (1970) to 73 years (2002) in men. If these trends continue, the number of fractures in elderly Finns will triple during the next three decades. Level of Evidence: Prognostic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence. Language: en

Update in the epidemiology of proximal humeral fractures.

The objectives of this study were to learn how hip fracture patients fall, and to compare the mechanics of their falls with those falls that did not result in hip fracture. In this way we sought to obtain reliable insight into the etiology and pathogenesis of hip fracture and fracture prevention. A total of 206 consecutive patients with fresh hip fracture and 100 controls were interviewed and examined between October 1994 and May 1996. The only inclusion criterion was that the fracture had occurred within 24 hours of hospital admittance. The control subjects were admitted from the same community after an accidental fall that did not result in hip fracture. The characteristics of the accident were determined by personal interview and examination of the patients within 24 hours of the event. In 98% of the hip fracture patients, the fracture was a result of a fall. The majority of the patients (76%) reported that they had fallen directly to the side. Forty-eight fracture cases had one or more eyewitnesses and their reports supported this observation. In 56% of the hip fracture patients, a fresh subcutaneous hematoma was seen on the greater trochanter of the proximal femur; such a hematoma was rare in the controls (6%) (P < 0.001), and this gave evidence for the direct impact of the greater trochanter during the fall of the hip fracture subjects. Most of the elderly fallers who fractured a hip did not manage to break the fall, e.g., with an outstretched arm. In conclusion, our results suggest that a typical hip fracture is the result of a fall and a subsequent impact on the greater trochanter of the proximal femur. The clinical implication of this finding is that effective prevention of hip fractures could be achieved by the diminution of the number and severity of falls of the elderly. We suggest that the severity of the falls (impacts on the greater trochanter) could be decreased by an external hip protector.

Majority of hip fractures occur as a result of a fall and impact on the greater trochanter of the femur: a prospective controlled hip fracture study with 206 consecutive patients.

Jari Parkkari

Papers

Epidemiology of hip fractures

Update in the epidemiology of proximal humeral fractures.

Majority of hip fractures occur as a result of a fall and impact on the greater trochanter of the femur: a prospective controlled hip fracture study with 206 consecutive patients.

Hip fractures in Finland between 1970 and 1997 and predictions for the future

Increasing number and incidence of low-trauma ankle fractures in elderly people: finnish statistics during 1970–2000 and projections for the future