The Strategy of Preventive Medicine

Obligatory reading for the Department of Health and Social Care.

Geoffrey Rose was an epidemiologist at the London School of Hygiene and Tropical Medicine from 1958 to 1991. He is best known for his work on cardiovascular disease. His impact on epidemiological concepts and thinking was significant. His book on the Strategy for Preventive Medicine is on the must-read list for TTE students interested in prevention and epidemiology.

In it Rose highlights that preventive interventions targeted at the individual often have a limited overall impact. For example, a meta-analysis of statin effects for primary prevention indicated a number-needed-to-treat (NNT) of 138 individuals taking statins for five years to prevent one death. He also highlighted that measures aimed at the population, such as screening, may offer little benefit to individuals.

Rose's "high-risk strategy" targets individuals with the highest risk factors, focusing on those most in need.

Part of the government's obesity strategy combines a "high-risk strategy" targeting obese individuals with weight loss drugs with the most risk factors. The strategy aims to give the drug to around 220,000 people in the first three years. The estimated cost is approximately £650 million.

The problem, though, is the increasing medicalisation of prevention, and any success is likely to be temporary and only target a small proportion of the population. Therefore, as a community-wide obesity intervention, it is doomed to fail. Rose’s intuition informs us that society would most benefit from targeting large numbers of individuals with a lower risk (of whatever diseases) from which most cases arise. When he taught, Rose used the example of reducing salt intake as a means of lowering cardiovascular risk for the entire population. These were the days before a pharmaceutical solution was available for most risk factors or ailments.

In response to this conceptual failure rooted in ignorance, razmatazz and media friendliness, we will expect to see a widening of the at-risk categories. If drugs were offered to people with a BMI > 35 and at least one obesity-related health problem, then potentially 3.4 million people would be eligible. The costs would then be exorbitant, amounting to approximately £10 billion annually, which is half the entire NHS drugs budget.

The government has therefore also turned to a population strategy that includes getting the supermarkets on board, with a new healthy food standard, to shift the population distribution of obesity. It believes that cutting the calorie count of a daily diet by just 50 calories would lift 340,000 children and 2 million adults out of obesity. We have no idea where this calculation comes from, but it sounds like more fanciful thinking from the government scriptwriters backed up by the latest AI logic.

Nanny state or worse?

However, this small benefit to each individual requires sustainable, long-term changes across the whole of society, which makes the change unlikely. Such interventions also require a robust evidence base to underpin the roll-out, which they don’t have. The evidence for whole-community interventions to prevent excessive population weight gain is limited - all trials are at risk of bias.

One of Rose’s key lessons is that "a large number of people at low risk can result in more cases of disease than a small number of people at high risk."

If the average weight of the population is increasing, we can predict that the proportion of people who will be obese will also rise. In effect, we are all responsible for the problem, as the average predicts the deviance.

The government should therefore start with the end in mind by reporting the average weight of the population. We could then determine whether the trajectory is improving or deteriorating, and whether any interventions are having an impact.

A new obesity strategy was unveiled by Boris Johnson in 2020, as the country was urged to lose weight to beat coronavirus (COVID-19) and protect the NHS. A new package of measures and 'Better Health' campaigns were announced. Like all the previous government obesity strategies, lacking an evidence base and a focus on sustainability, it failed. If only Wes Streeting knew that he was copying BoJo's strategy, including a raft of measures that similarly were untested.

Given the current government’s focus on prevention, Rose’s Strategy of Preventive Medicine should be obligatory reading in the Department of Health and Social Care. Until then, it’ll be more of the same.

This post was written by two old geezers who write their own posts.