長寿に寄与した医療の６段階　そしてその費用対効果

——乳児死亡率の改善だけではなかった寿命の物語——

つい先日も、廃業したクリニックの内装施設を買ってもらえないかと相談されました。思えば、病院やクリニックが経営難になる時代となりました。本来であれば、命のセイフティネットとなりうる医療機関は政治としても最優先されるべき政策。

しかし、ふと「寿命は医療の発展の中、どこで伸びたのか」という問いが浮かびました。

以下、その６段階を簡潔に整理してみます。

① 新生児・乳児死亡率の激減（1945–1965）

母子保健と周産期医療の整備により、出生直後の死亡リスクが劇的に低下しました。NICUや産科麻酔といった基盤投資は比較的少額で、平均寿命の底を強力に押し上げました。戦後、日本の寿命が一気に伸びた最大の力点はここにあると考えています。

② 感染症の制圧（1955–1975）

抗生物質と定期接種の普及で、肺炎・結核など致死的な感染症の影響が弱まりました。「死なない社会」の基礎体力がこの時期に形成されました。寿命は“運”ではなく、制度と技術に支えられるものへと変化していきます。

③ 外傷・救急医療の体系化（1965–1985）

救急車、救命救急センター、ATLSの導入により、外傷死や事故死が回避可能なものになりました。大規模なインフラ整備を要しましたが、救命の実感値は非常に高いものでした。医学と社会基盤がつながり始めた時期でもあります。

④ 循環器疾患の制圧（1985–2000）

高血圧治療の標準化、スタチンによる冠動脈疾患の管理、脳梗塞急性期治療などが確立しました。「中年期の崖」を越える手段が揃ったことで、寿命の伸びが再加速しました。治療の費用と効果の関係は比較的安定しており、費用対効果は中程度から良好といえます。

⑤ がん治療の精密化（2000–2015）

分子標的薬や免疫療法により、生存期間は延びましたが、治療コストも急上昇しました。個体差が大きく、延命効果の予測性が低いことから、費用対効果の不確実性が最も大きい段階です。この時期に、医療の進歩が医療経済と噛み合わない現象がはっきりと現れました。

⑥ 予防医療と老化ブレーキ医療（2010–現在）

禁煙政策、生活習慣介入、栄養指導などが進み、治療ではなく病気になる前に寿命の漏出を防ぐ技術が重視されるようになりました。医療者だけでなく、生活者自身が寿命の主体となる段階であり、費用対効果は極めて高く、持続可能性にも優れています。

費用対効果という観点での再配置

寿命の回収効率＝少ない投資で時間を取り戻せる領域として眺めると、次の順序になります。

新生児・母子保健（1945–65）
小さな投資で大きな寿命の伸びを生みました。

予防医療（2010–現在）
病気になる前の介入が医療費全体を押し下げます。

感染症対策（1955–75）
寿命の「最初の壁」を破り、死を日常から遠ざけました。

一方で、費用対効果が最も厳しかったのは、⑤がん治療の精密化です。
治療単価の高騰と、生存利益の個体差という構造的要因が背景にあります。

がん細胞が“個体の細胞史”である以上、治療は個別最適にならざるを得ず、医療経済学と摩擦を起こしやすい構造を持っています。

■ 例：分子標的薬

年間治療費：数百万円
延命効果：数ヶ月〜数年（個体差大）

■ 例：免疫チェックポイント阻害薬

年間：1,000万円規模も
奏効率：数%〜数十%（がん種で大きく差）

この“ばらつき”こそが、費用対効果を押し下げている本質。

医療経済学ではしばしば、がん治療薬はQALY（質調整生存年）あたりのコストが突出すると指摘されます。なぜ、費用対効果が悪くなるのか？

「がんは、個体の歴史そのものが病気になる」だから治療は、個体の数だけ最適化が必要になる。

この一文に、本質が凝縮されている。

◽ がん細胞の遺伝子変異は“個体の履歴”
◽ ターゲットが微細で高コスト
◽ 効果の指標が“延命”や“QOL改善”で測定が複雑
◽ 社会的費用（労働損失・介護など）が計算に入ると評価軸が揺れる

つまり、がん治療は“医療単体＝費用対効果”で測れない領域に踏み込んでいるといえるのです。

がん治療の時代は、医療の進歩に反比例して費用対効果が悪化した不思議な時代だった。国家単位の医療経済学と治療とが噛み合わなくなった瞬間だったともいえるのです。

Six Stages of Medical Advances That Contributed to Longevity — and Their Cost-Effectiveness

— The Story of Life Expectancy Was More Than Just Infant Mortality —

Just the other day, I was asked whether I might be interested in purchasing the interior facilities of a clinic that had gone out of business. It struck me that we have entered an era in which hospitals and clinics themselves struggle financially. Medical institutions, which should function as the ultimate safety net for life, ought to be among the highest priorities of public policy.

This led me to a simple but fundamental question:
At which points, within the development of medicine, did life expectancy actually increase?

Below is a concise overview of the six major stages.

① Dramatic Reduction in Neonatal and Infant Mortality (1945–1965)

Through the establishment of maternal and child health systems and advances in perinatal care, the risk of death immediately after birth fell dramatically. Foundational investments such as NICUs and obstetric anesthesia required relatively modest funding, yet powerfully lifted the lower bound of average life expectancy. I believe this period represents the single greatest driver behind Japan’s rapid postwar gains in longevity.

② Control of Infectious Diseases (1955–1975)

With the widespread use of antibiotics and routine vaccination, fatal infections such as pneumonia and tuberculosis lost much of their lethality. During this period, the basic resilience of a “society that does not easily die” was formed. Life expectancy began to shift from something governed by chance to something supported by institutions and technology.

③ Systematization of Trauma and Emergency Care (1965–1985)

The introduction of ambulances, emergency medical centers, and ATLS transformed trauma and accident-related deaths into largely preventable outcomes. Although this required substantial infrastructure investment, the perceived impact on survival was extremely high. This was also the period when medicine and social infrastructure began to meaningfully converge.

④ Control of Cardiovascular Disease (1985–2000)

Standardized hypertension management, statin-based control of coronary artery disease, and acute stroke treatments were established. With effective ways to overcome the “midlife cliff,” gains in life expectancy accelerated once again. The relationship between cost and benefit during this phase was relatively stable, yielding moderate to good cost-effectiveness.

⑤ Precision Cancer Therapy (2000–2015)

Molecular targeted therapies and immunotherapies extended survival, but at the cost of a sharp rise in treatment expenses. Due to large individual variability and low predictability of survival benefit, this stage carries the greatest uncertainty in cost-effectiveness. It was during this period that the misalignment between medical progress and health economics became unmistakably clear.

⑥ Preventive Medicine and “Aging-Brake” Medicine (2010–Present)

Anti-smoking policies, lifestyle interventions, and nutritional guidance have shifted emphasis away from treatment toward preventing the loss of lifespan before disease occurs. This is a stage in which individuals themselves—not only healthcare professionals—become the primary agents of longevity. Cost-effectiveness is extremely high, and sustainability is strong.

Reordering Medical Advances Through the Lens of Cost-Effectiveness

If we view longevity gains as a form of “lifespan recovery efficiency”—that is, areas where time can be reclaimed with minimal investment—the ranking becomes:

Neonatal and maternal health (1945–65)
→ Small investments generated enormous gains in life expectancy.

Preventive medicine (2010–present)
→ Pre-disease interventions reduce total healthcare expenditures.

Infectious disease control (1955–75)
→ Broke through the first major “wall” of mortality and pushed death out of daily life.

By contrast, the most challenging in terms of cost-effectiveness was ⑤ Precision cancer therapy.
This is driven by structural factors: soaring per-treatment costs and wide individual variation in survival benefit.

Because cancer cells represent an individual’s unique cellular history, treatment inevitably must be individually optimized—making friction with health economics almost unavoidable.

Examples

Molecular targeted therapies

• Annual cost: several million yen

• Survival benefit: several months to several years (high individual variability)

Immune checkpoint inhibitors

• Annual cost: sometimes exceeding 10 million yen

• Response rates: from a few percent to several tens of percent, depending heavily on cancer type

This very variability lies at the heart of declining cost-effectiveness.

In health economics, cancer drugs are often noted for their exceptionally high cost per QALY (quality-adjusted life year). Why does cost-effectiveness deteriorate?

Because “cancer is a disease in which an individual’s own history becomes the pathology.”
As a result, treatment must be optimized for each individual patient.

This single sentence captures the essence.

• Genetic mutations in cancer cells reflect an individual’s life history

• Targets are highly specific and therefore costly

• Outcomes are measured in survival extension and QOL improvement, making evaluation complex

• When societal costs (lost productivity, caregiving burden) are included, the evaluative framework itself becomes unstable

In other words, cancer treatment has entered a domain that cannot be adequately measured by “medical intervention = cost-effectiveness” alone.

The era of cancer therapy was a curious one: as medical progress advanced, cost-effectiveness paradoxically worsened. It may be seen as the moment when national-scale health economics and frontline clinical treatment ceased to align.