(5)公共健康方法-Public Health Approaches-公开课-关爱惟士
(5)公共健康方法-Public Health Approaches


Prof. Carol Brayne

Carol Brayne 教授

Public health defines prevention in several ways. There's primary prevention, secondary prevention and tertiary prevention.


Primary prevention is removing a cause of a disease, so the classic example is smoking and lung cancer. You remove the smoking, you remove the lung cancer that is attributed to smoking. There will be other lung cancers but they are not lung cancers caused by smoking.


Secondary prevention is early detection of a disorder at the point where you can change its natural history in a way that means the survival of the person with the early disease, or the quality of life of that person, is enhanced.


Tertiary prevention is when a disorder is fully manifest, is fully there, and it's about the treatment and the interventions, the care that we can provide that will improve the quality of life of that person in the presence of the disorder, and that includes palliative care, so that includes dying as well as we can.


Put those all together and you have the balance of care and activity required for a society to do the best it can with the resources that it has.


Secondary prevention is effectively screening. That can be done in an intensive case identification method or it can be done at a population level. To implement screening and/or early detection, we need really rigorous evidence and that is - in the UK and many countries such as the US, there are whole commissions looking at screening evidence.


At the moment, dementia is not one of the conditions that is recommended for screening, for systematic screening in the population. At present, our research investments across the world are focused on early detection and diagnostics. The implications of this kind of research is that there will be, in the future, some sort of screening program, whether it's applied at population level or within clinic settings. So we need an evidence base that is robust enough to meet the requirements of a screening program. At present, despite massive investment, the evidence is not sufficient for that and the implications in terms of cost are enormous for societies of implementing that kind of approach. It doesn't mean it won't be possible in the future but it needs to be thought about very, very carefully.


Primary prevention; we have evidence already about the approaches that we can take to reduce the conditions that are themselves risk factors for dementia. We have evidence of reduction in the prevalence, that is the proportion of people with dementia, in many countries and the incidence, that is the new occurrence of disease in populations. So we have that evidence from the US, from the UK, from some European countries. So we have good evidence that we can change the course of people's ageing and brain ageing.


We also have evidence on how to support people when they have dementia - that's the tertiary prevention side - increasing evidence about improvements in provision of care in care homes and the nature of the interventions that we can make to support people with dementia. So at present we have an imbalance of investment into what effectively would lead to a screening program for dementia and less investment into the primary and the tertiary, and it is clear from a public health point of view that we need to rebalance that.


Thinking about primary prevention of dementia, we need to take into account the context in which that prevention needs to occur. We have a constellation of different risk factors which relate to early, mid and later life, and we have very many different populations across the world that are experiencing ageing, so that the kinds of primary prevention activities that we might want to undertake in Australia might be very different in different groups within the population.


So for example, those in the clusters where, say, smoking and drinking excessively or to harmful levels is more prevalent, we might want to have a different approach to one where people are already doing physical activity and already having very good diets. That might relate to increasing the educational levels or one might think about groups in the population who are socially isolated. So these are all the different types of risk factors that one needs to take into account.


When we think about low and middle income countries or even a country like Japan, the profile of risk factors across the life course will have been very different for the people who are entering old age now. So it is absolutely not one size fits all, but a sense of needing to understand the risk factors that are operating for different age groups in different cultures and what is the evidence base for approaching those risk factors in those cultures.


If I was in the happy position of being in charge of the public health program in Australia, I would first want to map very carefully our knowledge of dementia in the population and different sectors of the population in different regions and different groups. I would then want to map our knowledge of the risk factor and protection factor profiles - so education is a key one there and social integration is another key one - to understand that across the population. Then I would want to bring to bear the evidence base that we have about how to change those factors and what works best, what our understanding is about what works best, at the individual level and at the population level and at the community level.


Then I'd want to create a community-based program which integrated that knowledge for a community and work with the community on the concerns of the community. And then, with embedded evaluation, look to see or basically implement combined interventions going from individual to population in those communities and then follow up the impact over time. So that would be integrating community and individual.


What I would also do, though, is look at the life course risk factors that we know we need national action on, and with that it would need to be a very careful discussion with the commercial sector. So sugar, alcohol and tobacco would probably need national activity.


Thinking from a whole population perspective and from the public health evidence, individually based interventions are pretty ineffective if one thinks about the resources required for individual interventions. So, for example, smoking cessation programs, although they're effective, they're nothing like as effective as doing things at community and population level, at national level. So when we think about the barriers, we need to think very carefully about each individual risk factor and what influences people's behaviours and what approaches we need to use. So a good example of the exultation to eat well is that, in socioeconomically-deprived areas of the UK, so my own nation's experience, fast food companies target opening in socioeconomically deprived areas. So the populations within those areas are at a particular disadvantage because what's available to them in their environment is an obesogenic environment. So it's very difficult to behave in a healthy way if you live in a place which has no areas for physical activity and also you don't have much money and low cost fast food outlets.

从大众群体的角度与从公共健康方面得来的统计数据来考虑,如果考量到个体干预所需的资源,进行个体基本干预效果会很不理想。举例,个体的戒烟项目,尽管它有效果,但是却不如社区,群体及整个国家层面来得有效果。由于这些不利因素,我们需要非常周全地考虑到每个不同个体的风险因素,影响个人行为的因素和其相应的对处方法。举一个恰当的例子,是饮食喜好的定位,在英国本土,快餐业把目标人群定位在这些低收入的经济底层地区。那结果就是生活在这些地区的人群被置于了一种不利的环境 — 一种容易引起肥胖的生活环境里。所以如果你生活在这样一个缺乏运动、低收入以及低成本不健康食物的地区,你很难拥有一个健康的生活方式。

So we have to work with communities and with businesses to shift the way that these things are operating within communities, because in the end businesses don't want to kill people and don't want to make their dementia risk higher. But they do need to make a profit, so we do need to think about what are the huge barriers that exist in terms of vested interests in our own ill health, and even in dementia occurrence. So we need to try to work to turn that around.