13. 解析に使⽤する介⼊ポイントを定義する
介⼊前期間と介⼊後期間を明確に区別する
We considered the year in which provincial legislation was
enacted to be the time point at which the intervention occured;
all years thereafter were considered post-intervention. In
Ontario and New Brunswick, where legislation was enacted
after Canadian cycling season (after September), we considered
the intervention to have occurred in the subsequent year.
RCT abstracts were retrieved from selected journals in two study
periods of 5 year each from January 2003 to December 2007
(pre-CONSORT), and from January 2010 to December 2014
(post-CONSORT).
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 18
4. 介⼊ポイント
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
J Clin Epidemiol 2016; 71: 11-17.
14. 解析に使⽤する介⼊ポイントを定義する
介⼊点が明確でない場合、実装にかかった期間
をよく定義する
We considered a lag period of 2 years before a true influence
of CONSORT-abstract guideline could be observed on quality of
abstracts [14-16]
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 19
4. 介⼊ポイント
J Clin Epidemiol 2016; 71: 11-17.
15. a. 情報源をリストアップする
b. データの完全性、妥当性、および時間の経過に伴
うdata coverageの変化をコメントする
We analysed annual counts of admissions to hospital for cycling
related injuries obtained from the National Trauma Registry
Minimum Data Set, ……. The registry contains personal and
diagnostic information on all admissions to acute care hospital
in Canada due to injury from 1994 onwads. The cause and
nature of each patient’s injuries are coded according to the
international classification of diseases (ICD-9, ICD-9-CM, and
ICD-10-CA), and up to 25 injuries are coded per patient.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 20
6. 情報源と測定⽅法
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
16. a. すべての統計解析⽅法を報告する
• 測定間隔
We included admissions to hospital due to a cycling injury that
occurred in the 15 years between 1 April 1994 and 31 March
2008 (……) and we summed counts by fiscal year ……
…… The dependent variable was bimonthly CONSORT-abstract
score mean expressed as percentage. Bimonthly blocks (30
blocks in each study period) were chosen as it permitted
inclusion of apploximately 15 abstracts per block.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 22
8. 統計解析
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
J Clin Epidemiol 2016; 71: 11-17.
17. a. すべての統計解析⽅法を報告する
• ⽤いた回帰モデル : ARIMA, linear, RDD
Secondly, using an over-dispersed Poisson segmented
regression analysis, we modeled the annual rates of
admissions to hospital for cycling related head injuries per total
admissions to hospital for cycling related injuries ……
For “ITS”, we used segmented linear regression analysis
to assess the significance of changes in intercept and slope of
the regression line before and after the introduction of the
CONSORT-abstract statement.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 23
8. 統計解析
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
J Clin Epidemiol 2016; 71: 11-17.
18. a. すべての統計解析⽅法を報告する
• 介⼊前、介⼊中、介⼊後のタイムポイントの数
タイムポイントとObservationの数は多いほど良い
推奨
介⼊前後にそれぞれ9タイムポイント
1タイムポイント当たり100 Observation
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 24
8. 統計解析
19. a. すべての統計解析⽅法を報告する
• 介⼊前、介⼊中、介⼊後のタイムポイントの数
We included admissions to hospital due to a cycling injury that
occurred in the 15 years between 1 April 1994 and 31 March
2008 (……) and we summed counts by fiscal year ……
…… The dependent variable was bimonthly CONSORT-abstract
score mean expressed as percentage. Bimonthly blocks (30
blocks in each study period) were chosen as it permitted
inclusion of approximately 15 abstracts per block.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 25
8. 統計解析
J Clin Epidemiol 2016; 71: 11-17.
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
20. b. 研究期間と予測に使⽤した解析前のタイムポイン
トを定義する
We included admissions to hospital due to a cycling injury that
occurred in the 15 years between 1 April 1994 and 31 March
2008 (……) and we summed counts by fiscal year ……
The time series was produced from daily ED records aggregated
to the number of visits per week for each outcome. This
produced 626 weeks (observations) in our time series, …. We fit
a regression line to each segment of the series (before and
after November 2002) using ……
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 26
8. 統計解析
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
BMC fam pract 2016; 17: 23.
21. c. ⾃⼰相関, ⾮局在性, 季節性をどのように検証し、
取り扱ったかを⽰す
⾃⼰相関
アウトカムの誤差項が1つ前/近傍のタイムポイントに
依存すること
Ljung-Boxのカイ⼆乗検定やDurbin-Watson統計量を⽤
いて検証
必要があれば補正をかける
Durbin-Watson statistic was used to examine for the
presence of first-order autocorrelation among serial
observations, and model was corrected for autocorrelation if
required.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 27
8. 統計解析
J Clin Epidemiol 2016; 71: 11-17.
22. c. ⾃⼰相関, ⾮局在性, 季節性をどのように検証し、
取り扱ったかを⽰す
⾮局在性
データが⼀定の範囲に収まらないこと
介⼊とは関連しないトレンドの存在を⽰唆
augmented Dickey-Fuller検定
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 28
8. 統計解析
23. c. ⾃⼰相関, ⾮局在性, 季節性をどのように検証し、
取り扱ったかを⽰す
季節性
アウトカムに季節に依存したノイズがのること
季節性が認められた場合、
† 季節性を⽣み出す単位となる時系列情報をモデルに
含める (ex: ⽉, 週)
† タイムポイントが多ければ移動平均をとる
We included fixed effect terms for year and season to
control for secular trends in the rate of avoidable visits to the
ED since long-term temporal changes may be correlated with
the FMG practice model.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 29
8. 統計解析
BMC fam pract 2016; 17: 23.
24. d. 介⼊効果が漸進的もしくは遅延している場合、ラ
グ期間を考慮する
• ラグ期間を解析から除外する
• ラグ期間を独⽴したsegmentとして扱う
• ARIMAモデルのramp関数を⽤いる
We considered a lag period of 2 years before a true influence
of CONSORT-abstract guideline could be observed on quality of
abstracts [14-16]; therefore, data from January 2008 to
December 2009 were not collected.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 30
8. 統計解析
J Clin Epidemiol 2016; 71: 11-17.
25. a. 解析されたそれぞれの群の参加者数と観察数を報
告する
Bimonthly blocks (30 blocks in each study period) were chosen
as it permitted inclusion of approximately 15 abstracts per
block.
A total of 424 RCT abstracts in pre-CONSORT and 467 in post-
CONSORT from the three selected pediatric journals were
assessed.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 31
9. 参加者
J Clin Epidemiol 2016; 71: 11-17.
27. a. 研究期間を通して測定されたアウトカムの数を報
告する
Between 1994 and 2008 we identified 66716 admissions to
hospital for cycling related injuries across the Canadian
provinces and territories. Head injuries accounted for 29.6 of
these, and over two thirds of head injured cyclists had a brain
injury.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 33
10. アウトカム
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
31. c. 変化量の絶対値と相対値と、その臨床的・政策
的・統計学的有意性を報告する。
The ITS analysis showed a significant change in slope of
regression line between two time periods [slope change 0.151
(95%CI, 0.004-0.298), p = 0.044]. Intercepts of regression lines
did not show a significant difference between two time periods
[intercept change -2.39 (95%CI, 4.93-0.157), p = 0.065].
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 38
11. Main Result
J Clin Epidemiol 2016; 71: 11-17.
32. 研究の⽬的と照らし合わせて、主たる結果を要約
する
Since 1994 in Canada the rate of bicycling injuries, including
those to the head, has decreased among young people. In six
provinces where helmet legislation was implemented, we
observed a steep decline in the rate of hospital admissions
for young people with cycling related head injuries (54%
reduction) compared with provinces and territories without
legislation (33% reduction). …… While these results
superficially suggest an important effect of helmet legislation,
after taking baseline trends into consideration we were
unable to show an independent effect of helmet legislation
on the rate of head injuries per hospital admission for cycling
related injury one year after the implementation of legislation…
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 39
13. Key result
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
33. 研究の⽬的と照らし合わせて、主たる結果を要約
する
Our study evaluated the impact of CONSORT-abstracts
statements on the reporting quality of RCT abstracts in three
high-impact general pediatrics journals. The results of our study
showed that overall reporting quality of RCT abstracts as
assessed by CONSRT-abstract checklist remain suboptimal
(<50%). The statement made no immediate impact on
reporting quality when assessed 2 years after the publication.
However, statistically significant impact was seen in reporting
quality when assessed over a 5-year period, hence implying
gradual adoption of guideline by pediatric research fraternity.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 40
13. Key result
J Clin Epidemiol 2016; 71: 11-17.
34. a. 潜在的な交絡要因と関連した⽂脈について記載す
る
• 研究期間中に⽣じた明らかなcointerventionにつ
いて議論する
Concurrent interventions that improve cycling safety combined
with municipality specific helmet legislation are two possible
explanations. The Canadian Cycling Association’s CAN-BIKE
programme to promote cycling safety, for example ……
Similarly, changes to cycling infrastructure over the study
period (for example, traffic calming, and designated bicycle
lanes and routs) could have confounded associations with
helmet legislation.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 41
14. ⽂脈
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
35. b. ⽐較解析の結果を議論する。⽐較条件を⽤いな
かった場合は、その蓋然性についてコメントする
we were unable to show an independent effect of helmet
legislation on the rate of head injuries per hospital admission for
a cycling related injury one year after the implementation of
legislation, either overall or according to the age group of
cyclists targeted by the legislation.
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 42
14. ⽂脈
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
36. 研究の⽬的や限界、類似の研究の結果、およびそ
の他のエビデンスを考慮に⼊れて、結果の全体的
な解釈を⽰す
5.5 Clinical and research implications and conclusion
Although our study showed statistically significant
improvement in quality of RCT abstract reporting in
pediatrics, the improvement was very slow and that too
not uniform across the high-impact journals. With this, we
can say that the probability of improvement may be remote in
the not-so-widely read journals. ……
2017/10/21 REQUIRE31 Interrupted Time Series Analysis 43
16. 解釈
J Clin Epidemiol 2016; 71: 11-17.
37. 2017/10/21 REQUIRE31 Interrupted Time Series Analysis 44
参考⽂献 (⽅法論的なところ)
Jandoc R, et al. Interrupted time series analysis in drug
utilization research is increasing: systematic review and
recommendations. J Clin Epidemiol 2015; 68: 950-6.
Cochrane Effective Practice and Organisation of Care
(EPOC). Interrupted time series (ITS) analyses. EPOC
Resources for review authors, 2017. available at:
http://epoc.cochrane.org/epoc-specific-resources-review-
authors
Bernal et al. Interrupted time series regression for the
evaluation of public health interventions: a tutorial. Int J
Epidemiol 2017; 46: 348-355.
38. 2017/10/21 REQUIRE31 Interrupted Time Series Analysis 45
参考⽂献 (研究)
Dennis J et al. Helmet legislation and admissions to
hospital for cycling related head injuries in Canadian
provinces and territories: interrupted time series analysis.
BMJ 2013; 346: f2674 doi: 10.1136/bmj.f2674
Chhapola V, et al. An interrupted time series analysis
showed suboptimal improvement in reporting quality of
trial abstract. J Clin Epidemiol 2016; 71: 11-7.
Carter R, et al. Effect of family medicine group on visits to
the emergency department among diabetic patients in
Quebec between 2000 and 2011: a population-based
segmented regression analysis. BCM fam pract 2016; 17: 23.
