Neurology. Charles H. Clarke
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Название: Neurology
Автор: Charles H. Clarke
Издательство: John Wiley & Sons Limited
Жанр: Медицина
isbn: 9781119235705
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Genetic
Huntington’s: a single gene disorder with high penetrance.
Epilepsy: complex interactions between presumed susceptibility genes.
Alzheimer’s: genetic influences in 10%, but not in the majority.
Genetic and Environmental
Parkinson’s disease: presumed genetic influences but susceptibility (curiously) reduced by smoking.Table 1.1 Population size and doubling times.Source: Data from The Population Reference Bureau, 2015CountryPopulation (millions)No. of births/motherDoubling time (years)Nigeria1076.223India9703.536China12361.867USA2682.0116Japan1261.5289UK601.7433Table 1.2 Incidence and point prevalence.Source: Data from various WHO sources; excludes shingles.DisorderIncidence (100 000/year)Point prevalence /100 000Migraine37012 100Acute stroke Subarachnoid haemorrhage TIA190 15 30900Epilepsy50710Dementia50250Parkinson’s disease20200Chronic polyneuropathies4024Bell’s palsy25Meningitis & infections15Brain tumours1010Trigeminal neuralgia41Multiple sclerosis Motor neurone disease4 290 4Muscular dystrophies16
MS: genetic susceptibility and geographic location. MS is more common in latitudes around 50°N and S of the equator, and rare in the tropics (0°–23.5° N and S). Clusters of MS cases, for example on the W coast of Ireland.
Evident and Preventable
In traumatic brain injury, many severe brain injuries have been prevented by car seatbelts.
Meningitis due to Haemophilus influenza, Streptococcus pneumoniae and Meningococci: immunisation.
Generally, where primary causes are poorly understood, causation can be divided into
predisposing factors (e.g. age, gender, genetic susceptibility)
enabling factors (e.g. hypertension, poor nutrition, inadequate medical care)
precipitating factors (e.g. exposure to infectious or noxious agent)
reinforcing factors (e.g. repeated or prolonged exposure).
Most neurological conditions are products of multifactorial influences, each of which alone would not cause the disease. It is thus helpful to study risk factors.
Mortality, Life Expectancy and Quality of Life
Mortality rate: the number dying of a condition divided by the number in the population.
This information is of limited value without knowledge of the overall death rate.
Life expectancy (median survival age) is often lowered in neurological disease, but data are complex.
Taking epilepsy, one study followed over 500 cases for >10 years. The overall mortality ratio was 2.1. The hazard ratio (HR), or risk of death, for epilepsy overall, was 6.2. Life expectancy was reduced by some 2–10 years.
Quality of Life
It is not enough to prolong survival. In high grade gliomas, radiotherapy is known to prolong life by about six months. Side effects are severe; the trade‐off between survival and quality of life (QoL) is important. One study showed that how well a patient was before radiotherapy was a good indicator of disability‐free life after it. For those already disabled, radiotherapy offered little gain.
Other Important Measures
Birth rate: number of live births/mid‐year population;
Fertility rate: number of live births/number of women aged 15–44 years (Figure 1.3);
Infant mortality rate: number of infant (<1 year) deaths/number of live births;
Stillbirth rate: number of intrauterine deaths after 28 weeks/total births;
Perinatal mortality rate: number of stillbirths + deaths in first week of life/total number of births.
Figure 1.3 Comparison of age‐specific fertility rates in women with treated epilepsy and general UK population of women in 1993
.
Burden of Illness
This means all negative impacts, though the words are often used to define cost. Whilst cost studies produce fiscal measurements, it is absurd to measure QoL in cash. Utility measures such as quality‐adjusted life years (QALYs) and disability‐adjusted life years [DALYs] try to quantify this burden (Table 1.3).
Cost of Illness Studies
The principal duty of a clinician is to provide individual care. However, doctors are now rightly involved in economic considerations. In any study of cost, analysis is of signal importance. Who was the study for, and who did it? The cost and burden for an individual have different parameters when compared with the effect on families, on health services and on society. Many studies are carried out from the point of view of society, with costs estimated in terms of lost employment, lost productivity and premature death, rather from the perspective of a patient, or their family.
Direct costs mean any resource used – medical costs of primary care, out‐patient and in‐patient investigation, drugs, residential and community care, training and rehabilitation.
Indirect costs are from lost economic production. They include premature mortality, dependency, unemployment and underemployment. The ‘human capital’ approach ascribes a monetary value to a person in terms of their potential productivity.
Table 1.3 DALYs (Disability‐Adjusted Life Year) for neurological and psychiatric conditions.
Source: Modified from Olesen and Leonardi 2003.
| Condition | DALYs × 10 | |||
|---|---|---|---|---|
| Europe | Wealthy countries a | India | Sub‐Saharan Africa | World |
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